Glossary of technical terms for the use of metallurgical engineers Terms starting with alphabet ‘R’
Glossary of technical terms for the use of metallurgical engineers
Terms starting with alphabet ‘R’
R2P2 – It means ‘reducing risks protecting people’. It is a document which describes the decision-making process of the health, safety and environment. It aims to make the procedures and protocols which the health, safety and environment follows transparent so as to ensure that the decision-making process of health, safety and environment, including risk assessment and risk management, is perceived as valid.
Rabbit ear – It is the recess in the corner of a metal-forming die to allow for wrinkling or folding of the blank.
Raceway – It is also called race. It is the groove or path in which the rolling elements in a rolling-contact bearing operate. In blast furnace, raceway consists of combustion zone in front of the tuyeres in a blast furnace. In this zone burning of the fuel takes place.
Rack – It is also called plating rack. It is a fixture used to hold work and conduct current to it during electroplating.
Rack and pinion – It is a type of linear actuator which comprises a circular gear (the pinion) engaging a linear gear (the rack). Together, they convert between rotational motion and linear motion. Rotating the pinion causes the rack to be driven in a line. Conversely, moving the rack linearly causes the pinion to rotate.
Rack and pinion gears – A straight bar with teeth cut straight across it, is called a rack. Basically, this rack is considered to be a spur gear unrolled and laid out fiat. Thus, the rack-and pinion is a special case of spur gearing. The rack-and-pinion is useful in converting rotary motion to linear and vice versa. Rotation of the pinion produces linear travel of the rack. Conversely, movement of the rack causes the pinion to rotate. The rack-and-pinion is used extensively in machine tools, lift trucks, power shovels, and other heavy machinery where rotary motion of the pinion drives the straight-line action of a reciprocating part. Normally, the rack is operated without a sealed enclosure in these applications, but some type of cover is normally provided to keep dirt and other contaminants from accumulating on the working surfaces.
Racking – It is a term which is used to describe the placing of metal parts to be heat treated on a rack or tray. This is done to keep parts in a proper position to avoid heat-related distortions and to keep the parts separated. It is also the process of arranging articles on a rack in order to transport them more efficiently through the galvanizing process.
Rack structure – It is a sturdy, built framework designed to hold, support, and organize items such as goods, equipment, pipes, or even building components, providing a stable, organized storage or support system. They can be simple steel structures in a warehouse, elevated platforms for pipes in an industrial plant, or even the primary load-bearing skeleton of a warehouse itself.
Radar – It means ‘radio detection and ranging. It consists of the techniques for observing the speed and position of objects by reflected radio waves.
Radar antenna – It is an equipment which emits and receives electro-magnetic waves to explore targets, determine range, locate objects, and control weapon systems, frequently incorporating a rotating mechanism for scanning. It consists of a radiator, metal reflector, and transmission line, with design features that influence the directionality and quality of the radar beam.
Radar beam – It is defined as a directed electromagnetic wave, generated by a vacuum electronic device (VED) such as a magnetron or Klystron, which emits radio waves or microwaves when stimulated by a high-voltage pulse.
Radar cross section – It is the effective reflecting area of a radar target, which varies with frequency, geometry, and surface composition.
Radar range – It is the distance to a radar-target, which can be calculated using parameters such as transmitted power, radar cross section, antenna gain, and signal-to-noise ratio, among others.
Radial-axial horizontal rolling machine – It is a type of metal forming technology which is used to produce seamless rings, employing both radial and axial rollers to control the ring’s dimensions during the rolling process, particularly for large-diameter and high-precision rings.
Radial basis function (RBF) – It is a three-layer neural network architecture comprising an input layer, a hidden layer, and an output layer, which utilizes basis functions centered around specific points to approximate complex functions. The Gaussian formula is frequently used because of its smoothness and infinite differentiability, facilitating superior approximation properties and faster calculations.
Radial blades – These blades refer to a type of fan blade design characterized by a rugged construction which can be flat or bent to improve efficiency and performance in several industrial applications, particularly in environments with high dust, temperature, or corrosive materials.
Radial centrifugal pump – It is a type of pump where the fluid exits the impeller in a radial direction, meaning perpendicular to the pump’s shaft, creating higher discharge pressures but typically smaller volume flow rates. In this pump, the fluid handled is conveyed radially, i.e., It enters through the suction pipe, is collected by the impeller, and then escapes vertically to the pump shaft from the pump’s impeller and through a spiral casing. This material handling method which uses centrifugal force enables higher pressures than can be achieved with axial pumps, where the fluids are conveyed axially, that is, parallel to the pump shaft.
Radial clearance – It is the internal looseness or gap in a bearing, measured as the distance one ring can move relative to another in the radial direction (perpendicular to the bearing’s axis). This space is critical for bearing function, allowing for thermal expansion during operation and preventing excessive heat, noise, or reduced performance from too little or too much clearance.
Radial coordinate – It is a measure of distance from a fixed point called the pole or origin, and it is a key component of polar and spherical coordinate systems. It represents how far a point is from the centre of the system and, along with an angular coordinate, uniquely defines the point’s position.
Radial crushing strength – It is a material property which describes a material’s resistance to compressive forces applied radially, meaning from the side, and is typically measured by a destructive test where a hollow cylinder is subjected to increasing radial load until fracture. It is the relative capacity, of a plain sleeve sample made by powder metallurgy, to resist fracture induced by a force applied between flat parallel plates in a direction perpendicular to the axis of the sample. It refers to the ability of a powder compact to resist fracture when a force is applied perpendicular to its axis, between flat parallel plates.
Radial depth – It refers to the measure of how deeply a cutting tool penetrates into the material in a radial direction during machining operations, which influences the harmonic content of the cutting forces.
Radial direction – It describes movement or orientation emanating from a central point outward in a straight line, or moving inward from a circumference to the centre, much like the spokes of a wheel. It is the direction along a radius and is frequently contrasted with axial (parallel to an axis) or tangential (along the curve) directions.
Radial distance – It is the straight-line measurement from a central point to another point, essentially the radius. This concept is used in several fields to describe the distance from an origin or central axis to a specific point, frequently within a circular or spherical system. For example, in a polar coordinate system, it represents the distance from the pole (origin) to a point.
Radial distribution function analysis – It is diffraction method which gives the distribution of inter-atomic distances present in a sample along with information concerning the frequency with which the particular distances occur.
Radial draw forming – It consists of the forming of sheet metals by the simultaneous application of tangential stretch and radial compression forces. The operation is done gradually by tangential contact with the die member. This type of forming is characterized by very close dimensional control.
Radial expansion – It refers to expansion or growth outward from a central point or axis, which can apply to different fields, including the radial swelling of materials because of the thermal or mechanical stress. The term ‘radial’ signifies the movement or dimension extending outwards, perpendicular to a central line or point.
Radial flow – It is the movement of a fluid or particles along a radius, from or toward a central point. In engineering, this is frequently seen in centrifugal pumps and turbines where fluid moves outward from the impeller’s centre, or in processes where fluid is distributed from a central source to surrounding areas.
Radial flow impeller – It is a type of impeller which directs fluid flow outward, perpendicular to the impeller’s axis of rotation, to generate pressure through centrifugal force. These impellers are characterized by blades aligned parallel to the impeller shaft and are used in applications needing high head and low flow rates, such as high-pressure pumping systems.
Radial-flow pump – Such a pump is also referred to as a centrifugal pump. The fluid enters along the axis or centre, is accelerated by the impeller and exits at right angles to the shaft (radially). An example is the centrifugal fan, which is normally used to implement a vacuum cleaner. Another type of radial-flow pump is a vortex pump. The liquid in them moves in tangential direction around the working wheel. The conversion from the mechanical energy of motor into the potential energy of flow comes by means of multiple whirls, which are excited by the impeller in the working channel of the pump. Normally, a radial-flow pump operates at higher pressures and lower flow rates than an axial-flow or a mixed-flow pump.
Radial force – It is a force that acts in a direction along a radius, either inward or outward from a central point. This type of force is crucial in understanding circular motion, mechanical components like pump impellers and transformer cores, and the design of bearings and other machinery.
Radial forging – It is a process using two or more moving anvils or dies for producing shafts with constant or varying diameters along their length or tubes with internal or external variations. It is frequently incorrectly referred to as rotary forging.
Radial friction welding (RFW) – It is a solid-state joining process where a rotating, solid, bevelled ring is radially compressed into a V-preparation created by the pipe ends, generating friction heat and forging the materials together without melting. The process adopts the principle of rotating and compressing a solid ring around two stationary pipe ends. The pipes to be welded are bevelled to provide a ‘V’ groove when they are butted together. They are then securely clamped to prevent axial and rotational movement. A solid, internally bevelled ring of compatible material with a bevelled angle that is less than that of the pipes is positioned around the pipe end.
Radial gap – It is a space between two circular or cylindrical components, measured in the radial direction (perpendicular to the axis of rotation), frequently found in pumps, turbines, or magnetic bearings to allow for fluid flow or support movement, e.g., it can be the space between a pump’s impeller and its casing or the air gap in a magnetic bearing system.
Radial grain flow – It refers to the directional orientation of metal grains, typically elongated and aligned, which flows outwards from a central point or axis, similar to spokes on a wheel.
Radial impeller – It is a rotating component with blades extending radially from a central hub, which takes in fluid axially and discharges it perpendicularly to the axis of rotation. This centrifugal action is generated by the impeller’s spinning motion, converting the mechanical energy from a motor into fluid velocity and pressure. Radial impellers are known for creating high pressure and are used in different applications, including industrial pumps, fans, and mixing equipment.
Radial lip seal – It is a radial type of seal which features a flexible sealing member, referred to as a lip. The lip is normally of an elastomeric material. It exerts radial sealing pressure on a mating shaft in order to retain fluids and / or exclude foreign matter.
Radial load – It is a force which is applied perpendicular to the axis of rotation of a mechanical component like a shaft or bearing. This type of load acts like a push or pull sideways on the component and is typically caused by the weight of rotating parts such as wheels, pulleys, or gears, or forces from things like conveyor belts.
Radial-load bearing – It is a bearing in which the load acts in a radial direction with respect to the axis of rotation.
Radial marks – These are macroscale ridges or thin ledges appearing as lines on a fracture surface. Radial marks are created under conditions of rapid crack growth. The lines frequently radiate from the fracture origin and are visible to the unaided eye or at low magnification. Radial marks can result from the intersection and connection of brittle cleavage fractures propagating at different levels. Alternatively, relatively tall, sharp-edged ridges can be created by small-scale ductile shear on intersecting planes. The appearance of radial lines varies considerably with the ductility of the material prior to and during fracture. In some microstructures (e.g., pearlitic steels), the lines can be poorly defined as diffuse ridges parallel to the direction of crack growth and may not be visible near the initiation site, but only after some growth of the crack front.
Radial piston pump – It is a type of positive displacement hydraulic pump which uses a set of pistons arranged in a circular, radial pattern around a central drive shaft to generate fluid flow and pressure. As the drive shaft rotates, a cam or eccentric component forces the pistons to move in and out of their cylinders, creating suction and discharge pressures to transfer hydraulic fluid.
Radial roll – It is also called main roll or king roll. It is the main driven roll of the rolling mill for rings in the radial pass. The roll is supported at both ends.
Radial roll forming process – It is a metal forming process where a small metal ring is continuously stretched and formed between rollers to produce a ring of larger dimensions, focusing on changing the ring’s thickness radially.
Radial rolling force – It is the action produced by the horizontal pressing force of the rolling mandrel acting against the ring and the main roll.
Radial stress – It refers to the stress acting toward or away from the central axis of a cylindrical object, such as a pipe or pressure vessel, and is a normal stress which acts along the radius.
Radial thrust – It is the lateral, outward-directed hydraulic force acting on a pump’s impeller, caused by a non-uniform pressure distribution around its circumference, particularly at off-design conditions. This uneven pressure results in a resultant force perpendicular to the pump shaft, which can cause shaft bending, bearing loads, and component wear in centrifugal pumps.
Radial tyre – It is defined as a type of tyre in which the body cord is arranged along the radial direction, featuring components such as tread, carcass, sidewall, belt ply, bead, and sealing ply, which collectively improve performance, service life, and fuel efficiency. Radial tyres are characterized by high elasticity, good wear resistance, low rolling resistance, and a high load-carrying capacity, though they can experience lateral stability issues and cracking.
Radial velocity – It is the component of an object’s velocity which is directed along the line of sight between the object and an observer, meaning it measures the rate at which the object is moving toward or away from the observer. This velocity is measured using Doppler shifts in the object’s light. A shift to longer wavelengths (red-shift) indicates motion away, while a shift to shorter wave-lengths (blue-shift) indicates motion toward the observer.
Radial wafer technique – It refers to methods and processes used to analyze and control variations in properties (like resistivity or thickness) across the radius of a wafer.
Radiant energy – It is the energy transmitted as electro-magnetic radiation.
Radiant heat – It is the heat which is communicated by radiation and transmitted by electro-magnetic waves.
Radiant intensity – It is the radiant power or flux emitted per unit solid angle expressed, e.g., in watts per steradian.
Radiant power (flux) – It is the energy emitted by a source or transported in a beam per unit time, expressed, e.g., in ergs per second or watts.
Radiant tubes – They consist of a method of heating a furnace without contaminating the furnace atmosphere with the products of combustion. The radiant tubes aim to transfer heat as uniformly as possible within the interior of the tube and transfer the heat within the furnace. The transfer of heat to the inner surface of the tube is dependent on the tube’s effective surface area. A tube with a nominal inside diameter of 100 millimeters can have a much higher effective internal surface area because of the surface roughness, which resembles small bumps and troughs. The internal surface area of the tube can also be increased using internal fins.
Radiant tube burner – It is also called radiant burners. It is an indirect-fired burner where combustion occurs within a heat-resistant tube, and the heat is transferred to the target material or process by radiation, preventing contamination of the atmosphere by combustion products. Radiant tube burner operates by combusting a fossil fuel, which heats a solid surface that radiates infrared (IR) energy to a load. This burner is normally used in a number of lower temperature heating applications, drying applications, and in industrial heat treatment applications, particularly when a controlled atmosphere is needed, such as in furnaces for annealing, hardening, or sintering. Both gas-fired and electric radiant heaters are normally used.
Radiant tube furnace – It uses long, heat-resistant tubes to transfer heat from combustion products to the materials being heated, preventing contamination of the furnace atmosphere with combustion gases.
Radiation – It is the process of emitting energy as waves or particles. The energy thus radiated is frequently used for ionizing radiation except when it is necessary to avoid confusion with non-ionizing radiation.
Radiation-absorbed dose (rad) – It is the quantity of energy (from any type of ionizing radiation) deposited in any medium (e.g., water, tissue, air). An absorbed dose of 1 rad means that 1 gram of material absorbed 100 ergs of energy (a small but measurable quantity) as a result of exposure to radiation. The related international system unit is the gray (Gy), where 1 Gy is equivalent to 100 rad.
Radiation area – It is a part of an installation accessible to employees in which there exists a radiation level of 0.075 millisieverts in any one hour over 1.5 millisieverts in any seven consecutive days.
Radiation control area – It is a defined area where specific protection measures and safety provisions are needed to control exposures or to prevent contamination during normal working conditions and to prevent or limit potential exposures.
Radiation damage – It is a general term for the alteration of properties of a material arising from exposure to ionizing radiation (penetrating radiation), such as x-rays, gamma rays, neutrons, heavy-particle radiation, or fission fragments in nuclear fuel material.
Radiation, direct – It means all radiation coming from within an X-ray tube and tube housing except the useful beam.
Radiation dose constraints – It is a numerical dose figure based on knowledge and assessment which is used as a planning aid for minimizing individual radiation dose.
Radiation hazard – It is a situation where persons can be exposed to radiation in excess of the maximum permissible dose.
Radiation heat transfer – It is the process where thermal energy is transferred through electromagnetic waves, without needing a medium, and can occur even in a vacuum. Unlike conduction and convection, which need a physical medium to transfer heat, radiation allows energy to travel directly from a hotter object to a colder one through space, like the sun warming earth. In the radiation heat transfer process, the thermal energy is exchanged between two surfaces obeying the laws of electromagnetics.
Radiation heat transfer coefficient – It is a proportionality constant which expresses radiant heat transfer between two surfaces in a manner analogous to convection, facilitating calculation by relating heat flow to a temperature difference, frequently in units of watts per square meter Kelvin. It quantifies the rate of heat transfer per unit area per unit temperature difference and is influenced by the temperature of the radiating surface and the net radiative exchange with the environment.
Radiation loss – It is a comprehensive term used in a boiler-unit heat balance to account for the conduction, radiation, and convection heat losses from the boiler to the ambient air.
Radiation protection – It is the protection of people from the harmful effects of ionizing radiation.
Radiation pyrometer – It is an instrument which measures the intensity of heat radiation emitted by a black body or an object with known emissive power to determine its temperature. There are two types namely (i) the total radiation pyrometer, which can measure temperatures at any level using infrared radiation, and (ii) the optical pyrometer, which operates at temperatures above 500 deg C using filtered red light.
Radiation shielding – It is reducing the level of radiation between a radioactive source and a person by interposing a shield of absorbing material.
Radiation source – It is a material or device that emits radiation, which can be in the form of waves or particles, and can be either natural or man-made.
Radiation thermometer – It is also known as a pyrometer or infrared thermometer. It is a non-contact device which measures an object’s temperature by detecting the infrared radiation it emits, without needing physical contact.
Radiation wave-length – It is the distance between two consecutive, identical points on a wave, such as the distance between two crests or two troughs, and is represented by the Greek letter lambda. It is a fundamental property of electromagnetic (EM) waves, like visible light or radio waves, and indicates the wave’s energy and behaviour. Shorter wavelengths, such as X-rays, carry higher energy and are more ‘particle-like’, while longer wave-lengths, like radio waves, are lower in energy and less harmful.
Radiative heat loss – It is the process where an object loses thermal energy by emitting electro-magnetic waves, specifically infrared radiation, to its surroundings. This form of heat transfer occurs independently of a medium, meaning it does not need air or other particles to travel through, and is the main way heat is lost from a hot object to a cooler environment, with the rate of loss dependent on the object’s temperature and surface properties, such as its emissivity.
Radiative heat transfer – It is the process of moving heat energy through space through electro-magnetic waves, a form of energy transfer which does not need a physical medium. Hot bodies emit these waves, which can then be absorbed by cooler bodies, leading to heat exchange. Examples include the sun warming the earth.
Radiator – It is a heat exchanger which is used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in automobiles, buildings, and electronics. A radiator is always a source of heat to its environment, although this can be for either the purpose of heating an environment, or for cooling the fluid or coolant supplied to it, as for automotive engine cooling and heating, ventilation, and air conditioning (HVAC) dry cooling towers. Despite the name, majority of the radiators transfer the bulk of their heat through convection instead of thermal radiation.
Radical – It is an atom, molecule, or ion which has at least one unpaired valence electron. With some exceptions, these unpaired electrons make radicals highly chemically reactive. Several radicals spontaneously dimerize. Majority of the organic radicals have short lifetimes. A notable example of a radical is the hydroxyl radical (OH-), a molecule which has one unpaired electron on the oxygen atom. Two other examples are triplet oxygen and triplet carbene (–CH2) which have two unpaired electrons. Radicals can be generated in a number of ways, but typical methods to produce radicals involve redox reactions. Ionizing radiation, heat, electrical discharges, and electrolysis. Radicals are intermediates in several chemical reactions, more so than is apparent from the balanced equations.
Radical process – It refers to chemical reactions involving species which contain one or more unpaired electrons, which are typically uncharged and show distinct properties and chemistries compared to cations or carbenes. These processes have evolved into a well-developed set of tools which are versatile and predictable, contributing considerably to the understanding of chemical reactions.
Radio – It is the technology of radio frequency devices.
Radioactive contaminants – These refer to materials which emit radiation and can be classified into two distinct properties namely water-soluble and insoluble. These contaminants are frequently associated with events such as nuclear power plant accidents and need specific technologies for remediation to restore affected environments.
Radioactive contamination – It is the deposition of, or presence of radioactive substances on surfaces or within solids, liquids, or gases (including the human body), where their presence is unintended or undesirable. Such contamination presents a hazard since the radioactive decay of the contaminants produces ionizing radiation (namely alpha, beta, gamma rays and free neutrons). The degree of hazard is determined by the concentration of the contaminants, the energy of the radiation being emitted, the type of radiation, and the proximity of the contamination to organs of the body. It is important to be clear that the contamination gives rise to the radiation hazard, and the terms ‘radiation’ and ‘contamination’ are not interchangeable. The sources of radioactive contamination can be classified into two groups namely natural and man-made.
Radioactive decay – It is the process by which an unstable atomic nucleus loses excess nuclear energy by emitting radiation in any of several forms, including as gamma radiation, as alpha or beta particles, or by ejecting electrons from its atomic orbitals.
Radioactive element – It is an element which has at least one isotope that undergoes spontaneous nuclear disintegration to emit positive particles, negative particles, or rays.
Radioactive isotope – It consists of varieties of an element possessing the same chemical characteristics but emitting detectable radiation’s by means of which they can be identified and traced.
Radioactive material – It is a compound or element which can emit any or all of the such radiation as alpha and beta particles, electrons, photons neutrons and gamma and all other emissions which produce ionization directly or indirectly. Radioactive materials refer to substances with unstable atomic nuclei which emit spontaneously ionizing radiation as they decay, releasing energy in the process. These are frequently mixed with hazardous waste from nuclear reactors, laboratories, or research institutions.
Radioactive particles – These are the sub-atomic particles and high-energy electro-magnetic waves emitted by unstable atoms during radioactive decay. The three main types of radiation are alpha particles (streams of helium nuclei), beta particles (energetic electrons), and gamma rays (high-energy photons). These particles carry substantial energy and can ionize other atoms and molecules, with their specific properties varying in mass, charge, and ability to penetrate matter.
Radioactive pollutants – These pollutants refer to the release of radioactive substances into the environment, causing contamination and posing risks to human health and the environment. These pollutants Radioactive materials originate from the (i) mining and processing of ores, (ii) use of isotopes in research and industrial activities, and (iii) radioactive discharge from nuclear power plants and nuclear reactors. These isotopes are toxic to the life forms since they accumulate in the bones, teeth and can cause serious disorders.
Radioactive pollution – It is defined as a form of physical, nuclear pollution to living organisms and the environment (hydrosphere, lithosphere, and atmosphere) arising from exposure to the release of ionizing radiation from radioactive elements such as uranium. Such releases occur as a result of radioactive decay of radioactive elements during (i) nuclear explosions and testing, (ii) disposal of nuclear waste, (iii) mining radioactive ores, and (iv) accidents at nuclear power plants.
Radioactive source – It contains radioactive material of a particular radio-nuclide (an unstable form of an element emitting radiation), which can vary based on the application for which the source has been manufactured. Radioactive sources emit ionizing radiation, typically in the form of alpha and beta particles, gamma rays or neutron radiation. Earlier, only radionuclides of natural origin, such as Radium-226 – an isotope of radium has been available for use. Today, radionuclides artificially produced in nuclear facilities and accelerators, including Caesium-137, Colbalt-60, and Iridium-192, are extensively used. These radioactive sources are used for medical, industrial, agricultural, research and educational purposes. Some examples of the application of radioactive sources include mapping underground sources of water, integrity testing of mechanical structures and measuring soil density for construction projects etc.
Radioactive waste – It is a waste material which emits energy as rays, waves, streams or energetic particles. It contains radionuclides and is no longer considered useful. It can be solid, liquid, or gas.
Radioactivity – It is the property of the nuclei of some isotopes to spontaneously decay (lose energy). Normal mechanisms are emission of or other particles and splitting (fissioning). It is the spontaneous emission of radiation, normally alpha or beta particles, frequently accompanied by gamma rays, from the nucleus of an unstable isotope. It is also, the rate at which radioactive material emits radiation. It is measured in units of becquerels or disintegrations per second. Other measurements are used (e.g., Sieverts) which relate to physiological effects.
Radio-analysis – It is an analytical technique, such as neutron activation analysis, which makes use of the radioactivity of an element or isotope.
Radio-chemistry – It is the branch of chemistry involving the study of radioactive substances and radioactivity, including the use of radioactive isotopes to study non-radioactive isotopes and ordinary chemical reactions
Radio direction finding (RDF) – It is the use of radio waves to determine the direction to a radio source. It differs from radar in that only the direction is determined by any one receiver; a radar system normally also gives a distance to the object of interest, as well as direction. By triangulation, the location of a radio source can be determined by measuring its direction from two or more locations.
Radio frequency – It consists of electromagnetic waves with frequencies less than that of infrared radiation. It is commercially important radio frequencies range from tens of kilohertz up to around a terahertz.
Radio frequency identification (RFID) – It is a wireless technology that uses radio waves to automatically identify and track objects, people, or animals by capturing data from a radio frequency identification tag with a radio frequency identification reader. Unlike barcodes, radio frequency identification does not need a direct line of sight for reading, allowing it to read multiple tags simultaneously and at varying distances, making it highly efficient for inventory and asset tracking.
Radio frequency identification (RFID) reader – It is an electronic device which uses radio waves to wirelessly read and capture data from a radio frequency identification tag to which it is in range. It generates radio signals to communicate with the tag, receiving information which can be used to identify and track objects or people. These readers are a fundamental part of an radio frequency identification system and are used in applications like inventory management, access control, and logistics, where they enable automated data collection without a direct line of sight.
Radio frequency interference (RFI) – It refers to unwanted signals which disrupt microwave instruments by interfering with the frequencies they measure, both internally and externally. It can be caused by different sources such as power circuits, signal voltages, and communication frequencies, impacting the accuracy of measurements in passive microwave applications.
Radio-frequency spectrometer – It is an instrument which measures the intensity of radiation emitted or absorbed by atoms or molecules as a function of frequency at frequencies from 10 kHz (kilohertz) to 100 GHz (gigahertz).
Radio-frequency spectroscopy – It is the branch of spectroscopy concerned with the measurement of the intervals between atomic or molecular energy levels that are separated by frequencies from around 10 to the power 5 hertz to 10 to the power 9 hertz as compared to the frequencies which separate optical energy levels of around 6 × 10 to the power 14 hertz.
Radio frequency (RF) spectrum – It is the portion of the electromagnetic spectrum for radio waves, normally ranging from 30 kilohertz to 300 giga-hertz, with frequencies lower than around 300 giga-hertz and wavelengths longer than around 1 millimeter. It is a finite and regulated resource used for several wireless communication technologies. Divided into frequency bands, each band has specific characteristics and applications, allowing for efficient use through techniques like frequency reuse for point-to-point communication.
Radiograph – It is a photographic shadow image resulting from uneven absorption of penetrating radiation in a test object.
Radiographic inspection – It is the examination of the soundness of an object by study of radiographs taken in different areas or of the whole object.
Radiographic testing – It is also called radiography inspection. It is the use of X-ray or gamma rays in studying the internal structure of objects to determine their homogeneity. It is normally used to determine whether a weld is sound. In case of a weld, it involves subjecting a weld or weld area to an X-ray source with an X-ray sensitive film plate on the under-side of the weld. The results are shown on the developed film (a photo-micrograph) and interpreted according to specification.
Radiography – It is a method of non-destructive inspection in which a test object is exposed to a beam of X-rays or rays and the resulting shadow image of the object is recorded on photographic film placed behind the object, or displayed on a viewing screen or television monitor (real-time radiography). Internal discontinuities are detected by observing and interpreting variations in the image caused by differences in thickness, density, or absorption within the test object.
Radio-isotope leak test system – It is a leak test system which uses a radioactive tracer gas and a detector for measuring the emission from the tracer.
Radioisotopes – Radioisotopes are radioactive isotopes of an element. They can also be defined as atoms which contain an unstable combination of neutrons and protons.
Radiology – It is the general term given to material inspection methods which are based on the differential absorption of penetrating radiation, either electromagnetic radiation of very short wavelength or particulate radiation, by the part or test-piece (object) being inspected. Because of differences in density and variations in thickness of the part or differences in absorption characteristics caused by variations in composition, different portions of a test-piece absorb different quantities of penetrating radiation. These variations in the absorption of the penetrating radiation can be monitored by detecting the unabsorbed radiation that passes through the test-piece.
Radio-nuclide – It is an unstable nuclide which hat emits ionizing radiation.
Radio-toxicity – It is the potential for radioactive substances to cause harm to living organisms because of the emitted radiation. It measures the biological damage from internal radiation, considering factors like the type and energy of radiation, the way the substance enters the body (ingestion, inhalation, or skin absorption), and how long the substance stays in the body. Unlike chemical toxicity, radio-toxicity is specifically related to the radioactive properties of the substance.
Radio transmitter – It is an apparatus designed to generate radio frequency electric current, which, connected to an antenna, can radiate energy through space.
Radium (Ra) – It a chemical element with atomic number 88. It is an alkaline earth metal. It is an element which is a radioactive decay product of uranium frequently found in uranium ore. Pure radium is silvery-white, but it readily reacts with nitrogen (rather than oxygen) upon exposure to air, forming a black surface layer of radium nitride (Ra3N2). It has several radioactive isotopes. All isotopes of radium are radioactive, the most stable isotope being radium-226 with a half-life of 1,600 years. When radium decays, it emits ionizing radiation as a by-product, which can excite fluorescent chemicals and cause radio-luminescence. For this property, it was widely used in self-luminous paints. Of the radioactive elements which occur in quantity, radium is considered particularly toxic, and it is carcinogenic because of the radioactivity of both it and its immediate decay product is radon.
Radius – Radius of a circle or sphere is any of the line segments from its centre to its perimeter. It is the distance from the centre of the circle to any point on its circumference. Radius also means to remove the sharp edge or corner of forging stock by means of a radius or form tool.
Radius elbows – These are fittings used in piping systems to change the direction of flow, with available types including long radius elbows, which provide smoother flow and have a radius 1.5 times the nominal size, and short radius elbows, which have a radius equal to the nominal size and create a larger pressure drop.
Radius of bend – It is the radius of the cylindrical surface of the pin or mandrel which comes in contact with the inside surface of the bend during bending. In the case of free or semi-guided bends to 180-degree in which a shim or block is used, the radius of bend is one-half the thickness of the shim or block.
Radius of curvature – It is the reciprocal of the curvature. For a curve, it equals the radius of the circular arc which best approximates the curve at that point. For surfaces, the radius of curvature is the radius of a circle which best fits a normal section or combinations thereof. In the case of a space curve, the radius of curvature is the length of the curvature vector.
Radius of gyration – It is the distance from an axis of rotation to a point at which the entire mass of an object is required to be concentrated to have the same moment of inertia as the object’s actual distribution of mass. It is a measure of how the mass is distributed around the axis of rotation, with a smaller radius of gyration indicating mass closer to the axis and a larger radius showing mass further away. The radius of gyration is denoted by the symbol ‘k’ and is measured in meters.
Radius vector – It is the vector which connects the origin of a chosen coordinate system to a given point, with its absolute value representing the distance of that point from the origin.
Radon – It is a heavy radioactive gas given off by rocks containing radium (or thorium). These rocks have existed since the formation of earth’s crust and radon is frequently the single largest contributor to an individual’s background radiation dose, and is the most variable from location to location. Radon is a noble gas (a group VIII element). Other members of the series are helium, neon, argon, krypton, and xenon.
Radon concentration – It refers to the quantity of radon gas present in the air, which can vary based on factors such as ventilation and the proximity of radium-226 sources in the surrounding soil and rock. High radon concentrations can pose serious health hazards, including an increased risk of lung cancer.
Radon survey – It is a geochemical survey technique which detects traces of radon gas, a product of radioactivity.
RAFT – RAFT is the ‘raceway adiabatic flame temperature’. The flame temperature is an important parameter since it affects the slag and metal chemistry, evaporation and recirculation of the alkali elements present, and the flow of metal in the hearth. It is difficult to measure the flame temperature and so it is normally calculated from an energy balance of the raceway zone. The calculated value is known as RAFT.
Rafter – It is one of a series of sloped structural members which extend from the ridge or hip to the wall plate, downslope perimeter or eave, and which are designed to support the roof deck and its associated loads. A pair of rafters is called a couple.
Raft foundation – It is also called mat foundation. It is a large, continuous, reinforced concrete slab which covers the entire footprint of a building, supporting the whole structure as a single unit by spreading the load over a wide area. It is a shallow foundation used in conditions with poor or weak soil, like soft clay or sand, to lower ground pressure and prevent differential settlement, effectively ‘floating’ the structure on the soil like a raft on water.
Rail – It is a steel bar extending horizontally between supports which is used as a track for rail road cars or other railway vehicles. The rail, as the most important component of the track superstructure, means the running surface, carrier and guiding element for the rolling wagons. It is the defining feature and most important component of the rail track. The main function of the rail is to provide a smooth and continuous level surface for movement and to provide guidance in lateral direction for movement of the wheels. Rails have asymmetric shape. Rail steel is used to make rails for the rail track as well as the tracks for moving equipments like cranes, transfer cars, charging and pusher cars in coke oven battery, and material handling equipment (stacker, reclaimers, and bender reclaimers) etc.
Railcar – It is a self-propelled railway vehicle is which designed to transport passengers. The term ‘railcar’ is normally used in reference to a train consisting of a single coach (or carriage, car, unit), with a driver’s cab at one or both ends.
Rail gauge – In rail transport, it ids the gauge of rail track. It is the distance between the two rails of a railway track. All vehicles on a rail network are required to have wheelsets which are compatible with the track gauge.
Rail infrastructure – It encompasses the entire complex system of tracks, bridges, tunnels, stations, and associated facilities which enable trains to operate safely and efficiently. This multi-disciplinary engineering includes civil, structural, and electrical components, along with signaling, power supply, and management systems, all designed to form a reliable network for both passenger and freight transport.
Railing – It is a protective barrier system made of posts and horizontal rails, designed to prevent people or vehicles from falling off a structure such as a bridge, balcony, or elevated walkway. Railings are built to specific heights and strength requirements, frequently incorporating a hand-rail for pedestrian support and a heavier guard-rail for vehicles, and are constructed from durable materials like steel, concrete, or aluminum to ensure public safety.
Rail mills – As the name suggest, rails mills are used for rolling of rail sections from the blooms.
Rail network – It refers to a system of inter-connected railway lines which are used for mass transportation of materials including movement of liquid metal. It has a significant carrying capacity. It connects different plant facilities and provides approaches to different production units. It greatly affects in-plant movement and traffic. Rail network is highly dependent on the plant general layout and can become very complex.
Rail profile – It is the cross-sectional shape of a rail, perpendicular to its length. The weight of a rail per unit length is an important factor in determining rail strength and hence axle loads and speeds. Weights are measured in kilograms per metre.
Railroad ballast – It is a layer of coarse granular material (like crushed stone or gravel) placed under and around railroad tracks to provide stability, drainage, and support for the rails and sleepers, ensuring a smooth and safe ride.
Railroad bridge – It is a specialized structural work designed and built to carry trains safely across an obstacle such as a river, ravine, or road, ensuring the continuity of the railway network. These bridges are critical infrastructure, needing constant maintenance and frequently involving complex designs which account for the immense loads of freight and passenger trains, using materials like steel and concrete to achieve stability and longevity.
Railroad car – It is a is a vehicle used for the carrying of passengers on a rail transport network. Such cars, when coupled together and hauled by one or more locomotives, form a train.
Railroad crane – This crane has flanged wheels for use on railroads. The simplest form is a crane mounted on a flat car. Most of these cranes are normally purpose built and have high lifting capacities. The design differs as per the type of work but the basic configuration is similar in all cases. The configuration normally consists of a rotating crane body which is mounted on a sturdy chassis fitted with flanged wheels. The body supports the boom and provides all the lifting and operating mechanisms. On larger cranes, a cabin for an operator is normally provided. The chassis is fitted with buffing and coupling gear to allow the crane to be moved by a locomotive, although several rail road cranes are also self-propelled to allow limited movement around a work site.
Railroad crossing – It is the point where a road or pathway intersects a railway line at the same level, also known as a grade crossing or level crossing. Engineered for safety, these intersections utilize passive or active warning devices, such as crossbuck signs, flashing lights, and gates, to alert users to potential hazards and prevent collisions between vehicles and trains.
Railroad safety – It refers to the comprehensive system of rules, technologies, and operational practices designed to prevent accidents and incidents, protect lives and property, and ensure the secure and efficient operation of railway systems. It involves safety protocols for the design, construction, operation, and maintenance of railway infrastructure and rolling stock, aiming to minimize risks and create a safety-conscious culture throughout the railway network.
Railroad switch – It is also called turnout. It is a mechanical installation enabling railway trains to be guided from one track to another. The most common type of switch consists of a pair of linked tapering rails, known as points (switch rails or point blades), lying between the diverging outer rails (the stock rails). These points can be moved laterally into one of two positions to direct a train coming from the point blades toward the straight path or the diverging path. A train moving from the narrow end toward the point blades (i.e. it is directed to one of the two paths, depending on the position of the points) is said to be executing a facing-point movement.
Railroad wheels and track materials scrap – Railroad wheels and track materials represent a class of scrap where impurities are normally low. Users of this scrap are also to consider that railroad wheels and track materials are being alloyed increasingly with chromium and molybdenum. Also, it is to be remembered that majority of the earlier cast iron wheels are being replaced with medium carbon steel forgings.
Rail sleepers – They are also called railroad ties, railway ties or crossties. They are an important railway component. They are rectangular supports which are placed across the track ballast, serving as a foundation for the rails, and helps to distribute the weight and vibrations of passing trains. Normally, the rail sleepers are always laying between two rail tracks to keep the correct space of gauge.
Rail steel – It is a specialized type of steel used in railway track construction. The properties of rail steel are achieved through control of carbon and manganese contents. Carbon content of rail steel can go up to a maximum of 0.82 % and manganese content up to a maximum of 1.7 %. The normal rails are made of steel containing 0.7 % carbon and 1 % manganese, which are called as carbon-manganese rail steel. Real steel has high strength, durability, and ability to withstand heavy loads and constant wear and tear. It is having a pearlitic structure based on its carbon-manganese composition. Its wear-resistant pearlite consists of alternating lamellae of soft iron and very hard iron carbide (also known as cementite). The smaller the spacing between cementite layers, the harder and more wear-resistant the rail steel is. Rails not only wear, they also break. Their inherent toughness is poor as a result of the presence of the brittle carbide phase. Fracture can occur from relatively minor stress-concentrating features inside the rail, or on the surface, as a result of manufacture or subsequent handling damage. Pearlitic rails have been developed almost to their limit. Now rails are also being made of a carbide free bainitic steel which is a tough rail steel with excellent wear resistance. Rail steel forms the main structural component of railway tracks, ensuring safe and efficient transportation of trains.
Rail stressing – It is a rail engineering process. It is used to prevent heat and cold tension after installation of continuous welded rail (CWR). Environmental heat causes continuous welded rail to expand and hence can cause the fixed track to buckle. Environmental cold can lead to the contraction of the fixed railway track causing brittleness and cracks. Before it is installed, the rail is altered by stretching with hydraulic tensors or heated to its stress-free temperature to make these dangerous problems less likely.
Rail track – It is a structure which allows trains to move by providing a smooth, low-friction surface for their wheels to roll on. It is also known as a railroad track, permanent way. It is made up of two parallel steel rails which are a fixed distance apart. The rails are connected by railroad ties, which are normally bolted to the rails. The ties are set into loose gravel or ballast, which helps transfer the load to the underlying foundation.
Rail traction – It refers to the system or method which is used to move trains or vehicles on rails, encompassing the power source, transmission, and mechanisms which generate the driving force.
Rail transport – It is a means of transport using wheeled vehicles running in tracks, which normally consist of two parallel steel rails. Rail transport is one of the two primary means of land transport, other being road transport. It is used both for passenger and freight transport, thanks to its energy efficiency and potentially high speed.
Railway tank car – It is also called tank wagon. It is a specialized type of railroad car designed to transport liquids and gases in bulk, frequently pressurized or non-pressurized, and insulated or non-insulated, depending on the specific commodity.
Railway wagons – These are unpowered railway vehicles which are used for the transportation of cargo. A variety of wagon types are in use to handle different types of goods, but all goods wagons in a railway network typically have standardized couplers and other fittings, such as hoses for air brakes, allowing different wagon types to be assembled into trains.
Rail welding – It is a process of joining railway rails together to create a continuous, strong rail line for high-speed, heavy-load traffic, replacing traditional joint bars. It involves heating the rail ends to a molten or plastic state and then fusing them under pressure to create a durable, metallurgical bond which increases the track’s lifespan and reduces noise, vibration, and maintenance needs.
Rail wheel – It is a type of wheel specially designed for use on railway tracks. The wheel acts as a rolling component, typically press fitted onto an axle and mounted directly on a railway carriage or locomotive, or indirectly on a bogie. The powered wheels under the locomotive are called driving wheels. Wheels are initially cast or forged and then heat-treated to have a specific hardness. New wheels are machined using a lathe to a standardized shape, called a profile, before being installed onto an axle. All wheel profiles are regularly checked to ensure proper interaction between the wheel and the rail. Incorrectly profiled wheels and worn wheels can increase rolling resistance, reduce energy efficiency, and can even cause a derailment. The International Union of Railways has defined a standard wheel diameter of 920 millimeters, although smaller sizes are used in some rapid transit railway systems and on ro-ro carriages.
Rain erosion – It is a form of liquid impingement erosion in which the impinging liquid particles are raindrops. This form of erosion is of particular concern to designers and material selectors for external surfaces of rotary-wing and fixed-wing aircraft.
Rainfall – It is defined as the total quantity of precipitation in the liquid form of water falling from the atmosphere onto the earth’s surface during a specific period. It refers to the falling of water droplets from condensed atmospheric vapour, and is measured by the depth of water collected in a rain gauge over a given time and area.
Rainfall intensity – It defines the rate at which rain falls, specifically the depth of precipitation collected over a given time period, such as millimeters per hour or inches per hour. It is calculated by dividing the total rainfall depth by the duration over which it fell.
Rainfall rate – It is a measure of the quantity of precipitation which falls over a given time period if the intensity is constant. It quantifies the intensity of rainfall, typically expressed in units like millimeters per hour or inches per hour. This rate is calculated by dividing the depth of the rainfall by its duration and indicates how much water is falling from the sky in a short period.
Rain forest – It is a dense, moist forest characterized by a high annual rainfall and frequently featuring tall, broad-leaved evergreen trees forming a continuous canopy. Rainforests are defined by their abundant rainfall, typically receiving 2,000 millimeters to 10,000 millimeters of rain annually.
Rain gauge – It is a meteorological instrument which collects and measures the quantity of liquid precipitation, such as rain, in a specific area over a given time period. It typically consists of a funnel which directs rain into a calibrated cylinder, which then records the total depth of rainfall, frequently expressed in millimeters or inches. This data is crucial for hydrologists and meteorologists for understanding weather patterns, managing water resources, and supporting agriculture.
Rain shadow – It is a region of relatively low rainfall on the leeward (downwind) side of a mountain range, where the mountains block the passage of rain-producing weather systems, casting a ‘shadow’ of dryness behind them.
Rainwater – It is the water which falls from the sky to the ground as rain. It is a form of precipitation in the water cycle. It forms when the sun’s energy evaporates water from the earth’s surface, which then rises into the atmosphere, cools, and condenses to form clouds. This atmospheric water then falls back to the earth’s surface as rain.
Rainwater harvesting – It is the process of collecting and storing rainwater which otherwise runs off into drains. It is a water conservation method which can be used for several purposes.
Rain gutter – It is also called surface water collection channel. It is a component of a water discharge system for a building.
Raise – It consists of a vertical or inclined underground working which has been excavated from the bottom upward.
Raised cosine pulse – It is a type of Nyquist pulse used in digital communication to minimize inter-symbol interference (ISI) by smoothly tapering the sinc function’s long tails, allowing for practical implementation and good trade-offs between bandwidth efficiency and robustness to noise and timing errors. It is characterized by a roll-off factor, which controls the transition band width in its frequency-domain response.
Raised face – The raised face is the most common used flange face. It is called raised face since the gasket is raised 1.5 millimeters to 6 millimeters above the bolt circle face. The flange facings are machine finished to meet the requirements of the standards and has unconfined gasket. They are suitable for average service conditions. For severe service involving high pressure, high temperature, thermal shock, or cyclic operations, this type of flange facing is normally not satisfactory.
Raised floor – It provides an elevated structural floor above a solid substrate (frequently a concrete slab) to create a hidden void for the passage of mechanical and electrical services. Raised floors are widely used in modern office buildings, and in specialized areas, where there is a requirement to route mechanical services and cables, wiring, and electrical supply. Such flooring can be installed at varying heights from 50 millimeters to heights above 1 meter to suit services which can be accommodated beneath. Additional structural support and lighting are frequently provided when a floor is raised enough for a person to crawl or even walk beneath.
Rake – It is the angular relationship between the tooth face, or a tangent to the tooth face at a given point, and a given reference plane or line. In geology, rake is the trend of an orebody along the direction of its strike. In railway terminology, a rake refers to a formation of coupled passenger coaches or freight wagons, essentially the train itself excluding the locomotive or engine. In geology, rake is the angle between a feature on a bedding plane and the strike line. Rake is also a long-handled tool with tines.
Rake angle – It is the angle of the cutting surface (or face) of a cutting tool relative to a reference plane perpendicular to the direction of cutting. It affects chip formation, cutting force, surface finish, and tool strength by changing the shape of the cutting edge. A positive rake angle makes the tool sharper and requires less force, while a negative rake angle increases the tool’s edge strength by making the cutting wedge more-blunt.
Rake classifier – It is a mechanical classifier consists of a rectangular tank with a sloping / inclined bottom. The tank is provided with movable rakes. The feed in the form of a suspension is introduced continuously near the middle of the tank. The lower end of the tank has a weir overflow from which the fines that are not settled leave with the overflow liquid. The heavy materials sink to the bottom of the tank. The rakes scrap the settled solids upwards along the bottom of the tank to the top of the tank. The reciprocating rakes keep the slurry in continuous agitation. The time of raking stroke is so adjusted that fines do not have time to settle and so remain near the surface of the slurry while the heavy particles have time to settle. Rake classifiers are also used for close circuit grinding.
Rake face – It is also called rake surface. It is the surface of a cutting tool against which the chips formed during cutting rub and slide away from the work-piece. This surface plays a critical role in chip formation, cutting efficiency, and the generation of heat during the operation. The angle of the rake face, known as the rake angle, influences several factors, including chip thickness, cutting forces, and power consumption.
Rake mechanism – Rake-mechanism of rolling mill cooling bed consists of (i) fixed straightening rakes, (ii) movable rake mechanism, and (iii) fixed rake-mechanism. Fixed straightening rakes are cast Iron toothed blocks, which receive the hot bars from the bar receiving mechanism. These fixed rakes help to straighten the bars, which are at a temperature of above 700 deg C. Movable rake mechanism consists of fabricated steel tooth rakes which are mounted on eccentric rollers to enable them to move in the x and y axis. The rakes have profile cut to suit the smallest and maximum size of bars. This mechanism collects the bars from the fixed straightening rakes and transfers them towards the delivery side of the cooling bed. Fixed rake-mechanism also consists of fabricated steel toothed rakes, which receive the bars from movable rake mechanism as the bars are transferred toward the delivery side of the cooling bed.
Raking, ladle – It means the practice of manually drawing off solid, or semi-solid slag, from the top of a ladle at the skimming station.
Ram – It is the moving or falling part of a drop hammer or press to which one of the dies is attached; sometimes applied to the upper flat die of a steam hammer. It is also referred to as the slide. It is also the moving parts of the pile hammer, consisting of a piston and a driving head, or driving head only. In a computer, RAM (random access memory) is temporary, high-speed memory that the CPU (central processing unit) uses to store data it needs for current tasks, allowing for quick access to information without searching long-term storage like a hard drive. It is a volatile memory, meaning its contents are lost when the computer loses power. More RAM allows a computer to handle more tasks simultaneously, improving overall performance and responsiveness.
Raman effect – It refers to the change in wave-length of monochromatic radiation, such as laser light, when it is scattered by molecules, with the shifts depending on the chemical structure of the sample. This phenomenon is crucial in Raman spectroscopy, which is complementary to infrared spectroscopy because of the differences in the underlying mechanisms.
Raman line (band) – It is a line (band) which is part of a Raman spectrum and corresponds to a characteristic vibrational frequency of the molecule being probed.
Raman radiation – It is also called Raman effect. It is the inelastic scattering of light by matter, resulting in a change in the light’s frequency and energy because of interactions with the vibrational and rotational modes of the molecules.
Raman scattering – It is also called Raman effect. It is the inelastic scattering of photons by matter, meaning that there is both an exchange of energy and a change in the light’s direction. Typically, this effect involves vibrational energy being gained by a molecule as incident photons from a visible laser are shifted to lower energy.
Raman shift – It is the displacement in wave number of a Raman line (band) from the wave number of the incident monochromatic beam. Raman shifts are normally expressed in units of per centimeter. They correspond to differences between molecular vibrational, rotational, or electronic energy levels.
Raman spectroscopy – It is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Raman spectroscopy is normally used in chemistry to provide a structural fingerprint by which molecules can be identified. Raman spectroscopy relies upon inelastic scattering of photons, known as Raman scattering. A source of mono-chromatic light, normally from a laser in the visible, near infrared, or near ultra-violet range is used, although X-rays can also be used. The laser light interacts with molecular vibrations, phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down. The shift in energy gives information about the vibrational modes in the system.
Raman spectrum – It is the spectrum of the modified frequencies resulting from inelastic scattering when matter is irradiated by a mono-chromatic beam of radiant energy. Raman spectra normally consist of lines (bands) at frequencies higher and lower than that of the incident mono-chromatic beam.
Ram extruder – It is an industrial machine which uses a ram or plunger, rather than a screw, to force a material through a die to create a desired shape. Material, frequently in powder or gel form, is fed into a chamber, heated, and then compressed by the ram into a constant volume, which is then pushed through a shaped die to produce continuous products like rods, tubes, or profiles.
Rammed earth – It is a sustainable construction method which creates durable, load-bearing walls by compacting a mixture of local earth (soil, sand, clay, gravel) between temporary formwork. Once the formwork is removed, it leaves a solid, monolithic wall with natural textures, high thermal mass for temperature regulation, and a low environmental impact. This technique has been used for centuries and is valued for its strength, fire resistance, and aesthetic qualities.
Rammed graphite moulds – These are casting moulds created by packing a mixture of graphite powder and binders around a pattern, offering a method to cast reactive materials like titanium without mould material reaction.
Rammer – It is a tool, either manual or powered, used to compact moulding sand around a pattern within a flask to create a dense, solid mould for casting molten metal. The sanding rammer process removes air pockets and voids from the sand, ensuring the final casting is free from defects and imperfections.
Ramming – It is the packing sand in a mould by raising and dropping the sand, pattern, flask on a table. Jolt squeezers, jarring machines, and jolt rammers are machines using this principle. It consists of packing foundry sand, refractory, or other material into a compact mass. It is the compacting of moulding (foundry) sand for forming a mould. In refractories ramming is a process of installing or shaping an unshaped refractory involving repeated impact.
Ram mix, ramming mix – It consists of unshaped refractory which is non-coherent before use, made up of aggregate, bond and if necessary, liquid, and placed by ramming (mechanical or manual) or vibration. As per the type of product, the main bond can be ceramic, chemical, or organic. Ram mixes are used as-delivered or after the addition of liquid(s).
Ramming refractory materials – These materials are in loose dry form with graded particle size. They are mixed with water for use. Wet ramming materials are used immediately on opening. Ramming materials are used mostly in cold condition so that desired shapes can be obtained with accuracy.
Ramming up – It is the process of packing the sand in the mould or core box with a rod or rammer.
Ramp – It is a sloping surface joining two different levels.
Ram-up core – It is a type of core which is positioned in a mould’s pattern or sand recess before the molding sand is rammed. It is then held in place by the compacted sand as the mould is formed, allowing it to make internal or external details on the final casting which is to be impossible to create otherwise. The key characteristic is that it is placed before ramming, unlike cores which are inserted after the mould is assembled.
Random alloy – It is a solid solution of atoms where different atomic species are distributed randomly throughout the material’s structure, leading to varying local environments and properties for each atom. This random atomic arrangement causes variations in local crystal fields and magnetic properties, and the resulting material shows a spectrum of properties influenced by this disordered atomic distribution rather than a single, uniform structure.
Random defects – These refer to different imperfections such as adsorbates, vacancies, and surface irregularities which disrupt the regular structure of a material’s surface, leading to disorder and a loss of translational invariance.
Random error – This type of error is normally because of the accumulation of a large number of small effects and can be of real concern only in measurements needing a high degree of accuracy. The cause of such error is unknown or not determined in the ordinary process of making measurement. Random error is an indeterminate error. This error takes place because of the causes which cannot be directly established because of random variations in the parameter or the system of measurement. Hence, there is no control over them. Their random nature causes both high and low values to average out. Multiple trials help to minimize their effects. Random errors can be analyzed statistically.
Random failures – These failures are normally attributed to hardware. They are failures occurring at a random time, which result in one or more of degradation of the component capability to perform its scope. Based upon historical data, random failures can be characterized by a parameter called failure rate. In other words, a random failure involves only the equipment. Random failures can occur suddenly without warning or be the outcome of slow deterioration over time. These failures can be characterized by a single reliability parameter, the device failure rate, which can be controlled and managed using an asset integrity program.
Random intermittent welds – These are intermittent welds on one or both sides of a joint in which the weld increments are made without regard to spacing.
Random orientation – It is a condition of a poly-crystalline aggregate in which the orientations of the constituent crystals are completely random relative to each other.
Random pattern – It is a winding with no fixed pattern. If a large number of circuits is needed for the pattern to repeat, a random pattern is approached. It is a winding in which the filaments do not lie in an even pattern.
Random sample – It is a subset of individuals or data points chosen from a larger population in a way that every member has an equal, independent, and known chance of being selected, frequently using tools like random number generators or tables. The goal is to create a statistically representative and unbiased sample, allowing people to make reliable inferences and conclusions about the entire population.
Random sampling – It is a technique for selecting participants from a larger population where each member has an equal and independent chance of being chosen, ensuring an unbiased and representative sample. This method, also known as probability sampling, allows people to draw statistical inferences about the entire population based on the characteristics of the randomly selected subset.
Random sequence – It is a longitudinal welding sequence wherein the weld-bead increments are deposited at random to minimize distortion.
Random signal – It is also known as a stochastic signal. It is a signal whose value at any given time cannot be predicted or described by an explicit mathematical relation, instead varying in an unpredictable way. Random signals are characterized by their statistical properties, such as probability distributions, and are fundamentally different from deterministic signals, whose values are precisely known for all time. Examples include noise in communication systems, speech signals, and earthquake signals.
Random variable – It is a parameter or variable which deviates from some measure of average performance or central tendency in a predictable way.
Random vibration – It is motion which is non-deterministic, meaning that the exact behaviour at a future point in time cannot be predicted, but general trends and statistical properties can be known. The randomness is a characteristic of the excitation or input, not the mode shapes or natural frequencies. Some common examples include an automobile riding on a rough road, wave height on the water, or the load induced on an airplane wing during flight. Structural response to random vibration is normally treated using statistical or probabilistic approaches. Mathematically, random vibration is characterized as an ergodic and stationary process.
Raney cobalt – It is a cobalt-based catalyst similar to Raney nickel. It is prepared by treating a cobalt-aluminum alloy with alkali. It is used for certain chemo-selective reductions, mainly in hydrogenation reactions.
Raney nickel – It is a heterogeneous hydrogenation catalyst, a fine-grained solid composed mainly of nickel derived from a nickel-aluminum alloy. It is used in organic chemistry for different reduction reactions, particularly hydrogenation.
Range – Range is the difference between the maximum and minimum values for which the instrument can be used for the measurement. The instrument range is stated by the manufacturer of the instrument.
Rangeability – It is the ratio of the largest flow coefficient to the smallest flow coefficient within which the deviation from the specified flow characteristic does not exceed the stated limits. A control valve which still does a good job of controlling when flow increases to 100 times the minimum controllable flow has a rangeability of 100 to 1. Rangeability can also be expressed as the ratio of the maximum to minimum controllable flow rates. In instruments, Rangeability is the valid operating range expressed as a percentage of its maximum value.
Range of a function – It is the set of all possible output values which the function produces when given an input from its domain. It is the collection of all the resulting ‘y-values’ or dependent variables for a given set of ‘x-values’ or independent variables. One can determine the range by finding the minimum and maximum possible output values, inspecting the y-values of a graph, or by analyzing the equation itself to identify the values the function can generate.
Range of stress (Sr) – It is the algebraic difference between the maximum and minimum stress in one cycle, i.e., Sr = Smax – Smin.
Range of transition – Transition is a change from one state or form to another, and the range of transition refers to the span of conditions or parameters over which this transformation occurs, such as the temperature range during a phase change, the frequency range in a filter, or the energy range in an atomic transition. The specific meaning of transition range depends heavily on the context, where it defines the scope of the change or the intermediate zone where a system shifts from one distinct behaviour to another.
Rank, coal – It is measured through a process called petrography whereby the amount of light which is reflected off the coal is quantified as its ‘reflectance’ (R). The higher is the reflectance, the higher is the coal rank.
Rankine cycle – It is an idealized thermodynamic cycle describing the process by which certain heat engines, such as steam turbines or reciprocating steam engines, allow mechanical work to be extracted from a fluid as it moves between a heat source and heat sink. Heat energy is supplied to the system through a boiler where the working fluid (typically water) is converted to a high-pressure gaseous state (steam) in order to turn a turbine. After passing over the turbine the fluid is allowed to condense back into a liquid state as waste heat energy is rejected before being returned to boiler, completing the cycle. Friction losses throughout the system are frequently neglected for the purpose of simplifying calculations as such losses are usually much less significant than thermodynamic losses, especially in larger systems.
Ranine cycle thermal efficiency – It is the ratio of the net-work output to the heat input, representing the percentage of heat energy converted into useful work by a power plant. It is calculated by dividing the net work done by the cycle by the heat supplied to the boiler. Higher thermal efficiency indicates higher effectiveness in converting energy from a heat source into mechanical or electrical power.
Rankine-Hugoniot relations – These are the equations derived from the conservation of mass, momentum, and energy, used to relate five quantities (pressure, density, internal energy, particle velocity, and shock wave velocity) during shock wave propagation.
Ranking of coal – It is a classification system based on its degree of coalification, which describes the natural process of buried plant matter being transformed into denser, drier, more carbon-rich coal under increasing heat and pressure. Coal is ranked from lowest (lignite) to highest (anthracite) based on properties like carbon content, moisture content, and heating value, with higher-rank coals having more carbon, less moisture, and a higher heating value.
Rankinite – It is a mineral composed of the chemical formula Ca3Si2O7, a calcium silicate containing calcium, oxygen, and silicon. It is a rare mineral, found in clinkers of high-temperature processes, and is of growing interest as a potential alternative binder for use in environmentally friendly cement and concrete because of its lower production temperature and potential for carbon di-oxide sequestration.
Raoult’s law – It is a law of thermodynamics which states that the partial pressure of each gaseous component of an ideal mixture of liquids is equal to the vapour pressure of the pure component multiplied by its molar fraction in the mixture.
Rapeseed oil – It is a brownish-yellow oil extracted from the seeds of the rapeseed plant, used as a lubricant because of its surfactant properties, which create a friction-reducing film between surfaces. These surfactants, including unsaturated organic acids like oleic acid, form stable damper films by forming adhesive bonds on metal surfaces, making it valuable for lubricating friction pairs in hydraulic systems and other machinery.
Rapid crack propagation (RCP) – It is a phenomenon where a brittle crack travels at high speed, frequently exceeding the speed of sound in the material, causing a long, catastrophic failure in materials like plastic pipes or frozen lakes. This type of fracture occurs when a pressurized system has enough stored energy to sustain crack growth and is often initiated by a sudden impact or a pre-existing flaw. Factors such as temperature, material properties, pipe size, and internal pressure influence considerably whether rapid crack propagation occurs.
Rapid elasticity – It is the ability of a system to quickly and automatically provision or de-provision computing resources, such as processing power, memory, and storage, in response to real-time changes in demand. This automatic adjustment ensures that applications have the necessary resources to handle sudden traffic spikes or increased workloads without user intervention, leading to high availability, cost savings from avoiding over-provisioning, and efficient resource management.
Rapid filtration – It is a water purification process which uses rapid sand filters to remove suspended solids and turbidity at a high flow rate, utilizing physical processes like adsorption and straining. After pre-treatment steps such as coagulation and flocculation, water passes through a bed of sand and gravel, followed by a final disinfection process like chlorination. The filters are regularly cleaned by back-washing to maintain their efficiency.
Rapid gravity filter – It is also known as a rapid sand filter. It is a water purification method which uses gravity to draw water through a bed of granular media (like sand or anthracite) at a high flow rate, effectively removing suspended particles and impurities.
Rapid hardening cement – As the name indicates, it develops the strength rapidly than ordinary portland cement. This cement develops at the age of three days, the same strength as that expected from the ordinary portland cement in seven days. With this cement the initial strength is higher, but they equalize at 2-3 months. Setting time for this type is similar for that of ordinary portland cement. The rapid rate of development of the strength is due to higher C3S (tri calcium silicate) and lower C2S (di calcium silicate) and due to finer grinding of the cement clinker (the minimum fineness is 3250 sq cm per gram. Rate of heat evolution is higher than ordinary portland cement due to the increase in C3S and C3A (tri-calcium aluminate), and due to its higher fineness. Chemical composition and soundness requirements are similar to those of ordinary portland cement. The uses of this cement is indicated where a rapid strength development is desired (to develop high early strength, i.e. its 3 days strength equal that of 7 days ordinary portland cement, for example (i) when formwork is to be removed for re-use, (ii) where sufficient strength for further construction is wanted as quickly as practicable, such as concrete blocks production, sidewalks and the places which cannot be closed for a long time, and repair works needed to construct quickly, (iii) for construction at low temperatures, to prevent the frost damage of the capillary water, (iv) this type of cement does not use at mass concrete constructions.
Rapid heating – It is the swift and substantial increase of an object’s or substance’s temperature using high-energy flux densities to achieve faster and more efficient processes, frequently to reduce energy consumption or enhance productivity. Technologies like lasers, induction, and infrared radiation enable rapid heating by delivering concentrated thermal energy, enabling applications from chemical reactions and metal fabrication to battery testing.
Rapid manufacturing – It refers to using technologies like additive manufacturing (3D printing) and high-speed CNC (computer numerical control) machining to produce end-use parts directly from digital designs, bypassing costly and time-consuming traditional tooling methods. It enables fast, flexible production of low-volume or customized products, including structural components and tools, by adding material layer-by-layer or using automated, subtractive processes. The term is frequently used interchangeably with or seen as the evolution of rapid prototyping and rapid tooling, aiming to accelerate the entire product development and production cycle.
Rapid mixing tank – It is a short, highly turbulent tank used in water treatment to quickly and uniformly disperse coagulants and other treatment chemicals into raw water, neutralizing negative particle charges to initiate the formation of larger, settleable particles called flocs. This process, also known as flash mixing, happens in fractions of a minute to ensure chemicals are evenly distributed, setting the stage for successful flocculation and solids removal.
Rapid omni-directional compaction (ROC) – It is a powder consolidation technique that uses a non-gaseous pressure transmission medium, typically a fluid, to apply pressure from all directions, resulting in rapid and uniform densification of the powder.
Rapid prototyping – It is a relatively new field in manufacturing which involves techniques / devices that produce prototype parts directly from computer-aided design (CAD) models in a fraction of the time needed using traditional techniques. The prototypes are used as form models (i) to check the touch and feel of the part, (ii) as fit models, to verify geometry and alignment of the part in its intended application, and (iii) in some cases as function models assembled onto a working mechanism to test the ability of the part under design to perform its intended duty. The prototyped object can also be a mould or a pattern for secondary techniques which produce preproduction or production tooling. Rapid prototyping techniques normally produce prototypes by decomposing a three-dimensional CAD model into parallel cross sections. Typically, each cross section is constructed atop the previous cross section, building the part layer by layer from layers that are 0.1 millimeter to 0.2 millimeter thick. The layers are bonded together either before or after cutting or as a natural consequence of layer formation. The construction materials available for these techniques include photo-polymerizable or thermo-plastic resin, paper, wax, and metal or ceramic powder. Secondary operations expand the list of available materials to include castable metals and certain forms of composites.
Rapid quenching – It the process of quickly cooling a heated material, frequently by immersing it in a medium like water or oil, to achieve a specific microstructure, such as increased hardness, strength, and wear resistance, while preventing slower, undesirable transformations. This rapid cooling rate is critical for creating different material properties than those formed during slow cooling.
Rapid rewetting – It refers to the swift reintroduction of water to a previously dry soil or ecosystem, frequently after a period of drought or drainage, which can trigger a surge in microbial activity and nutrient mineralization.
Rapid solidification – It is the cooling or quenching of liquid (molten) metals at rates that range 10 to the power 4 deg C per second to 10 to the power 8 deg C per second.
Rapid solidification techniques – These techniques have gained significant attention in the field of materials science because of their potential to produce materials with unique microstructures and properties. The primary objective of rapid solidification is to achieve a high cooling rate during the solidification process, which results in the formation of a fine-grained microstructure. This is achieved by applying external cooling or by quenching the liquid metal to achieve rapid cooling rates in the range of 10 to the power 4 deg C per second to 10 to the power 8 deg C per second. The process of rapid solidification can be achieved using different techniques, including melt spinning, spray forming, gas atomization, and laser processing.
Rapid thermal processing (RTP) – It is a semiconductor manufacturing process which heats silicon wafers to temperatures exceeding 1,000 deg C for not more than a few seconds. During cooling wafer-temperatures are to be brought down slowly to prevent dislocations and wafer breakage because of the thermal shock. Such rapid heating rates are frequently attained by high intensity lamps or lasers. These processes are used for a wide variety of applications in semiconductor manufacturing including dopant activation, thermal oxidation, metal reflow and chemical vapour deposition.
Rapid tooling (RT) – It is a manufacturing process which uses rapid prototyping techniques to quickly create moulds, dies, or other tools for producing parts at a lower cost and faster speed compared to conventional methods. It is classified as either direct (where the tool is built directly) or indirect (where a 3D-printed pattern is used to create the tool) and is ideal for low-to-medium volume production runs and prototyping.
Rapid tool wear – It refers to the accelerated and unexpected deterioration of a cutting tool, occurring much faster than normal, frequently because of high cutting speeds, improper cutting conditions, or specific machining processes. Unlike gradual wear which can be predicted, rapid wear can lead to premature tool failure, impacting machining efficiency, part quality, and increasing costs.
Rapping – It is the practice of striking or shaking a pattern after it is been pressed into a sand mould to loosen its grip on the sand, making it easier to remove without damaging the mould or the pattern itself. This slight jarring action enlarges the mould cavity, so the pattern is intentionally made smaller than the final casting to account for this change, a reduction known as rapping allowance.
Rapping allowance – It is also called shake allowance. It is a negative allowance added to a pattern to compensate for the slight enlargement of the mould cavity which occurs when the pattern is rapped or shaken to loosen it from the rammed sand for easier withdrawal. The pattern is made smaller than the final casting dimensions to account for this increase, ensuring the desired casting size is achieved after the pattern is removed.
Rapping bar – It is a pointed bar or rod made of steel or other metal, which is inserted vertically into a hole in a pattern, or driven into it, then struck with a hammer on alternate sides to cause vibration and loosening of the pattern from the sand.
Rapping plate – It is the metal plate attached to a pattern to permit rapping for removal from the sand.
RAR – It is a proprietary archive file format which supports data compression, error correction and file spanning. The name RAR stands for Roshal archive. The software is licensed by WinRAR GmbH. It is proprietary archive format for compressing and storing multiple files.
Rare earth drum magnetic separator – It is an industrial equipment with a rotating, non-magnetic drum containing powerful permanent rare-earth magnets, used to separate ferrous and para-magnetic materials from dry or wet streams of bulk materials. Its high-intensity magnetic field allows it to attract and remove even weakly magnetic, finely ground particles which other separators can miss, making it ideal for applications requiring high product purity.
Rare-earth elements (REE) – They also called the rare-earth metals or rare earths, and sometimes the lanthanides or lanthanoids, although scandium and yttrium, which do not belong to this series, are normally included as rare earths. Rare earth elements are a set of 17 nearly indistinguishable lustrous silvery-white soft heavy metals. Compounds containing rare earths have diverse applications in electrical and electronic components, lasers, glass, magnetic materials, and industrial processes. Scandium and yttrium are considered rare-earth elements since they tend to occur in the same ore deposits as the lanthanides and show similar chemical properties, but have different electrical and magnetic properties.
Rare earth garnets – These are also known as rare-earth iron garnets (RIGs). These are ferrimagnetic insulators with the chemical formula R3Fe5O12, where ‘R’ represents trivalent rare-earth ions, and are known for their unique magnetic properties and potential in spintronics and magneto-optical applications.
Rare earth magnets – These are permanent magnets made from alloys of rare earth elements, known for their exceptionally strong magnetic fields and high energy density. The two main types are neodymium magnets, which are the strongest, and samarium-cobalt magnets, which offer better heat resistance. They are crucial components in several high-tech devices and industrial applications.
Rare earth metals – They are also known as rare earth elements. These are relatively scarce minerals. They consist of a group of 17 chemically similar metals that includes the elements scandium and yttrium (atomic numbers 21 and 39, respectively) and the lanthanide elements (atomic numbers 57 through 71).
Rare earth phosphor – It is a luminescent material composed of a host matrix containing a small quantity of rare earth elements (such as europium, cerium, or terbium) as activators. These phosphors absorb energy and re-emit it as light, with the rare earth ions providing highly efficient, specific, and colour-tunable luminescence. They are crucial in modern technologies like white-light LEDs (light-emitting diodes), fluorescent lighting, and display screens
Rare earth roll-magnetic separator – It is a high-intensity, dry separation equipment which uses powerful, permanent neodymium-iron-boron (NdFeB) magnets in a roller assembly to capture and separate weakly magnetic materials, such as mica or iron-stained minerals, from non-magnetic materials. The system consists of a high-intensity magnetic head pulley with NdFeB magnets and steel poles, which creates an intense magnetic field. As dry material passes over the conveyor belt, weakly magnetic particles are attracted to the roll and held to the belt, while non-magnetic particles fall away.
Rare earths – These are a group of 17 metallic elements, including the 15 lanthanides, plus scandium and yttrium, which are crucial for high-tech industries because of their unique magnetic, optical, and electronic properties. Although not truly ‘rare’ in terms of abundance, they are difficult to extract and separate from one another because of their similar chemical properties and close geological association. They are necessary for manufacturing products like magnets, electronics, batteries, lasers, and in clean energy technologies. Rare earths are categorized into Light Rare earths (lanthanum to samarium) and Heavy Rare earths (europium to lutetium). They are key enablers for technologies looking to lower emissions, reduce energy consumption, as well as improve efficiency, performance, speed, durability, and thermal stability. They are also a key component in technologies that seek to make products lighter and smaller. Rare earths react with other metallic and non-metallic elements to form compounds each of which has specific chemical behaviours. This makes them indispensable and non-replaceable in many electrical, optical, magnetic, and catalytic applications.
Rare earth wet drum magnetic separator – It is an industrial equipment which uses powerful neodymium-iron-boron (rare earth) magnets housed within a rotating stainless-steel drum to continuously separate fine, weakly magnetic particles (such as iron ore, magnetite, or contamination) from slurries and low-viscosity liquids. These separators create a strong, high-gradient magnetic field to attract and capture the magnetic materials, which are then conveyed out of the product stream by the drum’s rotation for collection, resulting in purified concentrate and waste.
Rare event probability – It refers to the likelihood of an event occurring which has a very small chance of happening, frequently expressed as a low numerical value. While the probability is small, it is not zero, meaning the event can still occur. The challenge lies in accurately estimating these low probabilities, especially when data on such infrequent occurrences is scarce, leading to the development of specialized techniques like extreme value theory and advanced sampling methods in fields such as engineering and system safety.
Rarefaction – It is the region in a medium experiencing a substantial reduction in density and pressure, frequently seen in the propagation of longitudinal waves like sound or shock waves, or in the behaviour of gases at low pressures where molecular spacing increases and continuous flow is disrupted. It is a fundamental concept in acoustics for understanding sound transmission and in fields like gas dynamics and MEMS (micro-electro-mechanical systems) for analyzing fluid behaviour.
Rarefaction effect – It refers to the phenomena and consequences which occur when a gas is reduced considerably in density, leading to non-continuum flow behaviors such as velocity slip at boundaries and altered flow resistance, particularly in microchannels and hypersonic flight. This condition is quantified by the Knudsen number (Kn), which compares the mean free path of gas molecules to the system’s characteristic length scale. As ‘Kn’ increases, the gas becomes more rarefied, and continuum flow assumptions break down.
Rarefied environment – It refers to a gas environment characterized by low total pressure, where molecular flow and its characteristics, such as density and distribution, are more meaningful indicators.
Rarefied gas – It is a gas with considerably low molecular density, meaning the molecules are far apart because of the low pressure. This low density causes the mean free path (the average distance a molecule travels before colliding) to become comparable to the size of the container or flow system, so the gas no longer behaves as a continuous fluid but instead as individual molecules, needing different mathematical models for analysis.
Rare gases – These are more accurately known as noble gases or inert gases, are a group of unreactive, mono-atomic chemical elements located in Group 18 of the periodic table, including helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). Their inertness stems from their stable electron configuration with a full outer shell, making them very unlikely to form chemical bonds. They are called ‘rare gases’ since they exist in very small quantities in the earth’s atmosphere.
RASA slag granulation system – It is a water quenching method for rapidly cooling molten blast furnace slag into small, granular particles suitable for recycling as raw material, frequently in the cement industry. This process is named after its developer, RASA corporation. The system works by introducing molten slag and pressurized water jets into a granulation chamber, which breaks the slag into tiny, water-carrying particles that are then dewatered and conveyed for further use. Dewatering facilities of the RASA is composed of several filtering beds, which are made up of layers of different particle size pebble bed at the bottom.
Ratchet drive – It is a shaft or valve which is operated by means of a ratchet mechanism. The ratchet delivers an intermittent stepped rotation through a gear in one direction only.
Ratcheting – It consists of progressive cyclic inelastic deformation (growth, for example) which occurs when a component or structure is subjected to a cyclic secondary stress super-imposed on a sustained primary stress. The process is called thermal ratcheting when cyclic strain is induced by cyclic changes in temperature, and isothermal ratcheting when cyclic strain is mechanical in origin (even though accompanied by cyclic changes in temperature).
Ratchet marks – It consists of lines or markings on a fatigue fracture surface that results from the intersection and connection of fatigue fractures propagating from multiple origins. Ratchet marks are parallel to the overall direction of crack propagation and are visible to the unaided eye or at low magnification.
Ratchet mechanism – It is a mechanical device which allows continuous motion in only one direction while preventing movement in the opposite direction, using a toothed wheel (the ratchet) and a pawl that engages the teeth. This allows for controlled movement, like tightening a bolt with a ratchet wrench, or for the intermittent advancement of a part, such as in fishing reels.
Ratchet wheel – It is a toothed wheel which, in conjunction with a ‘pawl’ or ‘click’, allows continuous rotational motion in one direction while preventing it in the opposite direction. The pawl engages with the saw-shaped or sloped teeth of the wheel, falling into the tooth’s depression as the wheel turns forward and catching on a steeper edge to block backward motion. This mechanism is used in tools like ratchet wrenches, winders, and mechanical clocks to achieve one-way motion and hold a position.
Rate – It refers to the change in a quantity (like distance, velocity, or concentration) over a unit of time, basically a measure of how fast something is happening or changing. For example, the rate of reaction, which is the speed at which a chemical reaction occurs, or the volumetric flow rate, the volume of fluid passing through a surface per unit time.
Rate analysis – It is the analytical process of determining the unit cost of a specific construction activity or item of work by breaking it down into its basic components such as materials, labour, equipment, and overhead costs. This method involves quantifying the necessary resources and pricing them individually to establish an accurate and defensible unit rate, ensuring proper budgeting and cost control for a project.
Rate constant (k) – It is the proportionality constant in a chemical reaction’s rate law, which relates the reaction’s rate to the molar concentrations of its reactants. It specifically represents the rate of the reaction when the concentrations of all reactants are equal to unity, and it reflects the intrinsic speed of the reaction at a given temperature. A higher value of the rate constant indicates a faster reaction, while a smaller value indicates a slower reaction.
Rate contract – It is a standing offer between a buyer and a supplier to provide specified goods at a fixed price for a set period, without specifying a total quantity. The supplier is obligated to fulfill purchase orders for specific quantities at the agreed-upon rates when placed during the contract’s validity. Rate contracts are frequently used for common, regularly demanded items with stable prices, typically in government and large organizations.
Rated capacity – It is the manufacturers stated capacity rating for mechanical equipment. For example, the maximum continuous capacity in kilograms of steam per hour for which a boiler is designed.
Rate determining step – The overall rate of a reaction is frequently approximately determined by the slowest step which is known as the rate-determining step. For a given reaction mechanism, the prediction of the corresponding rate equation (for comparison with the experimental rate law) is frequently simplified by using this approximation of the rate-determining step.
Rated flow coefficient – It is the flow coefficient of the valve at rated travel.
Rated frequency – It defines the specific AC (alternating current) frequency at which an electrical device, such as a switchgear or a component, is designed to operate effectively and reliably. This designated frequency, typically 50 hertz or 60 hertz for power systems, ensures that the equipment functions correctly within its specified operational parameters, such as maintaining insulation integrity and proper performance.
Rated horsepower – It is the maximum power an engine, motor, or device can sustain continuously and safely under specified conditions without overheating or failing. It is a measure of an engine’s sustained output power rather than its peak or momentary power, and it indicates the power the device is designed to produce for extended periods, providing a key specification for its intended use.
Rated speed – It is the number of blows per minute of the hammer when operating at a particular maximum efficiency.
Rated travel – it is the distance of movement of the closure member from the closed position to the rated full-open position. The rated full-open position is the maximum opening recommended by the manufacturers.
Rated voltage – It is the specified voltage at which electrical equipment is designed to operate safely and reliably for its entire intended lifespan, frequently indicated on the equipment’s nameplate. It serves as a performance reference point and defines the upper limit for acceptable system voltage, ensuring the equipment functions correctly without experiencing faults or damage.
Rate equation – It is also known as the rate law or empirical differential rate equation. It is an empirical differential mathematical expression for the reaction rate of a given reaction in terms of concentrations of chemical species and constant parameters (normally rate coefficients and partial orders of reaction) only.
Rate kinetics – It studies reaction rates, i.e., the speed at which reactants are converted into products over time. It focuses on how fast a reaction proceeds and the factors, such as temperature, pressure, and reactant concentration, that influence this speed. Kinetics also uses rate data to understand the step-by-step molecular pathways, or mechanism, by which a chemical reaction occurs.
Rate limiting factor – It is a condition which prevents an overall process from running at a faster rate, which can arise from mechanical limitations, such as poor mixing or low heat transfer area, or chemical factors like slow kinetics or mass transfer issues.
Rate law – It is a mathematical equation which describes how the rate of a chemical reaction depends on the concentrations of its reactants. It is also known as the rate equation.
Rate-limiting step – It is the slowest step in a chemical reaction which involves more than one step. The rate of this step determines the overall reaction rate.
Rate of blow-down – It is a rate normally expressed as a percentage of the water fed.
Rate of creep – It is the slope of the creep-time curve at a given time determined from a Cartesian plot.
Rate-of-oil-flow – It is the rate at which a specified oil will pass through a sintered porous compact under specified test conditions.
Rate of reaction – It is the speed at which a chemical reaction takes place. It is defined as proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of a reactant per unit time. Rates of reaction can vary dramatically.
Rate of rise – It is the time rate of pressure increase at a given time in a vacuum system which is suddenly isolated from the pump by a valve. The volume and temperature of the system are held constant during the rate of rise measurement.
Rate of strain hardening – It is the rate of change of true stress with respect to true strain in the plastic range.
Rate sensitivity – It refers to strain rate sensitivity, which describes how a material’s mechanical properties, like flow stress or strength, change in response to the speed of deformation (strain rate). A material’s strain rate sensitivity quantifies its tendency to either strengthen or weaken at different loading speeds, which is crucial for designing structures and components that must perform reliably under various conditions, from slow creep to high-impact events.
Rat-hole mining – It is also called rat mining. It is a process of digging used to extract coal, where a narrow hole is manually dug by extraction workers. The practice is banned. Rat-hole mining technique is a procedure of digging manually wherein the worker involved in extraction can hardly crawl in and out, as a narrow tunnel is dug 1 meter to 1.25 meter in depth. This technique is basically of two types namely (i) side cutting method which is normally followed on slopes of hills by navigating through coal seams deposited on the rock layers and visible on the outer surface of rock and normally in darkish brown or black banded, and (ii) box cutting method which involves digging a round shape or square shape pit with a width of 5 square metre and depth of around 120 meters.
Rating – It specifies the performance limits or characteristics of a component or system, such as its maximum power, voltage, current, or its ability to withstand certain conditions, like fire or corrosion. Ratings are set by manufacturers as guidelines to define the operational parameters under which a piece of equipment is designed to work reliably and safely.
Rating, conveyor belt – It is the minimum belt breaking strength of a belt in Newtons per millimeter of belt width.
Rating, equipment – Rating of an equipment refers to the specified limits or characteristics assigned by the manufacturer, defining the equipment’s safe and optimal performance under specific conditions, often displayed on a rating plate.
Rating life – It is currently the fatigue life in millions of revolutions or hours at a given operating speed which 90 % of a group of substantially identical rolling-element bearings survive under a given load.
Ratio level of measurement – It is the most sophisticated and highest level of measurement, incorporating all features of nominal, ordinal, and interval scales. It is characterized by its ability to be categorized, ordered, and have equally spaced intervals, but most importantly, it possesses a true or absolute zero point that signifies the complete absence of the variable being measured. This true zero allows for meaningful calculations of ratios between values, such as stating that 4 objects is twice as many as 2 objects.
Rational analysis – It is a systematic, logic-based approach to making design decisions and evaluating risks, frequently involving computational methods to assess objective data and identify optimal solutions. It emphasizes objective evaluation and the use of formal techniques to analyze trade-offs, aiming to produce “reasonable and satisficing outcomes that meet goals within practical, frequently resource-limited, constraints.
Rational efficiency – It is another term for exergy efficiency or second-law efficiency, which measures a system’s performance against an ideal, reversible process. It quantifies how much of the theoretical maximum useful output (work, cooling, etc.) is actually achieved, accounting for irreversibilities like friction and heat transfer losses. A higher rational efficiency indicates a system is closer to its thermodynamic ideal and has greater potential for improvement.
Rationalization – It is a process used to merge similar packaging lines, allowing the benefits of a smaller inventory and improved economies of scale.
Rationale – It is the explicit explanation of the underlying reasoning, justification, and argumentation behind specific design decisions, choices, and processes. It details why certain alternatives have been considered and rejected, what trade-offs have been evaluated, and how these factors ultimately have led to the current design or approach. The main purpose of documenting rationale is to provide a comprehensive record which helps future teams understand, maintain, and modify engineered systems and to support designers in generating better solutions.
Rational sampling – It is the process of collecting data into subgroups, where the items within each subgroup are produced under similar, stable conditions, representing a specific ‘snapshot’ of a process at a given time. The goal is to minimize variation from special causes of variation within a subgroup, focusing instead on common cause variation (natural, random variation) to gain insights into process stability and predict long-term variations using control charts.
Ratio pyrometer – It is also known as a two colour pyrometer. It is a non-contact temperature measurement device which measures the ratio of infrared radiation emitted by a target at two different, closely spaced wave-lengths, allowing for temperature determination independent of emissivity variations.
Rattail – It is a surface imperfection on a casting, occurring as one or more irregular lines, caused by expansion of sand in the mould.
Raw data – It is information in its original, unprocessed, or unanalyzed form, collected directly from a primary source, and has not been subjected to any cleaning, organization, or manipulation to extract insights. It is considered the fundamental building block from which insights and conclusions can be drawn after further processing.
Raw material – It is also known as a feed-stock, or unprocessed material. It is a basic material which is used to produce goods, finished goods, energy, or intermediate materials that are feed-stock for future finished products.
Raw material consumption – It refers to the use or utilization of raw materials by the processes of the organization over a specific period. It can be defined as the total volume of resources extracted, imported, and processed to support a process, with a broader understanding including the environmental impact of their extraction, processing, use, and disposal. This concept is crucial for tracking resource use, calculating a process’s material footprint, and developing strategies for resource management and sustainability.
Raw material cost – Normally it is the major component of the production cost. Raw material cost is dependent on quality of raw material, yield of product, handling loss, moisture content of the raw material, and wastages associated with the use of the raw material etc. Raw material cost is also influenced by the level of waste recycling.
Raw material feed – It refers to the process of feeding unprocessed or primary materials (feedstock) to a processing system at a controlled rate to ensure efficient and consistent production. It involves mechanical equipment like feeders to transport different forms of materials, from solids and powders to liquids and gases, from storage to the point of processing, ensuring a continuous flow for operations like manufacturing, batching, and filling.
Raw material input – It is the basic, frequently natural, substance which is used as a foundational element in a production process to be transformed into a finished product. These inputs, which can include mined minerals, are essential for manufacturing and are subject to rigorous analysis and accounting within the organizational inventory and production planning systems.
Raw material preparation – It is the process of taking natural or semi-processed materials and transforming them through actions like cleaning, grinding, screening, separating, and purifying to make them suitable for use in manufacturing or production processes. This preparation ensures materials are finely ground, thoroughly mixed, and free from contaminants, which is necessary for efficient chemical reactions and the production of a high-quality final product. It refers to the initial processes which transform unprocessed or minimally processed substances into a usable form for manufacturing or other production processes.
Raw material substitution – It refers to the practice of replacing conventional raw materials with alternatives which minimize waste generation and environmental impact, such as using recycled materials or less hazardous chemicals in production processes. This approach aims to improve efficiency and create environmentally friendly products by reformulating and redesigning the material inputs.
Raw material use – It refers to the consumption of all raw material resources in a process.
Raw natural gas – It is a mixture of hydrocarbons, carbon di-oxide, hydrogen sulphide, nitrogen, water, and other impurities which is extracted from production wells, which can include crude oil, gas, and condensate wells. It can also originate from unconventional sources and needs processing to produce a methane-rich gas by removing impurities.
Raw refractory dolomite – It refers to the natural, unheated form of the mineral dolomite [CaMg(CO3)2] used as a refractory material, meaning it is resistant to high temperatures and maintains its structural integrity under extreme heat conditions.
Raw water – It is the water in its natural state, prior to any treatment for drinking. It is the water supplied to the plant before any treatment.
Rayleigh channels – These channels are wireless communication channels characterized by scattering paths between the transmitter and receiver, where the phase of each path varies uniformly and independently, typically modeled as a zero mean Gaussian random variable.
Rayleigh’s criterion – It refers to a condition for oscillations in a system, defined by the work done during one cycle being greater than zero, indicating instability and the occurrence of oscillations when the heat release rate and pressure are considered.
Rayleigh number – In fluid mechanics, the Rayleigh number for a fluid is a dimensionless number associated with buoyancy-driven flow. It is also known as free convection. It characterizes the fluid’s flow regime i.e., a value in a certain lower range denotes laminar flow and a value in a higher range denotes turbulent flow. Rayleigh number is the product of the Grashof number (Gr), which describes the relationship between buoyancy and viscosity within a fluid, and the Prandtl number (Pr), which describes the relationship between momentum diffusivity and thermal diffusivity.
Rayleigh scattering – It is the scattering of electro-magnetic radiation by independent particles which are smaller than the wavelength of radiation.
Rayleigh step bearing – It is a stepped-pad bearing having one step only in each pad.
Rayleigh waves – These are a type of surface acoustic wave which travel along the surface of solids. These waves can be produced in materials in several ways, such as by a localized impact or by piezo-electric transduction, and are frequently used in non-destructive testing for detecting defects. Rayleigh waves are part of the seismic waves that are produced on the earth by earthquakes. When guided in layers they are referred to as Lamb waves, Rayleigh–Lamb waves, or generalized Rayleigh waves
Rayon – It has regenerated cellulose composition. It is slightly stronger than cotton, but tensile strength is lowered by water. Its chemical resistance is similar to cotton. It also has high moisture absorption and hence, poor dimensional stability. It is susceptible to mildew attack. It is practically non-existent in conveyor belt today.
Razor streak – It is an impurity, metallic or non-metallic, which is trapped in the cast product and elongated subsequently in the direction of working. It can be revealed during working or finishing as a narrow streak parallel to the direction of working.
R-chart – It is also called range chart. It is a type of control chart which is used in statistical process control (SPC) to monitor the variability (range) of a process over time by plotting the range of variation within samples taken from the process. R-charts help identify whether a process is in a state of statistical control by monitoring the range of variation within sub-groups. The chart includes control limits, which are lines that define the expected variation of the process.
RCM analysis – RCM (Reliability Centered Maintenance) analysis carefully considers the questions which are (i) what does the system or equipment do and what are its functions, (ii) what functional failures are likely to occur, (iii) what are the likely consequences of these functional failures, and (iv) what can be done to reduce the probability of the failure, identify the onset of failure, or reduce the consequences of the failure.
R-curve – In linear-elastic fracture mechanics, it is a plot of crack-extension resistance as a function of stable crack extension, which is either the difference between the physical crack size, or the effective crack size, and the original crack size. R-curves normally depend on sample thickness and, for some materials, on temperature and strain rate.
RDX – RDX stands for Royal Demolition Explosive. It is the common name for hexahydro-1,3,5-trinitro-1,3,5-triazine. It a powerful secondary explosive, also known as cyclonite or hexogen. It is a white, crystalline solid used industrial applications as a high explosive. RDX serves as a base charge for detonators and is a key component in plastic explosives like Composition C-4, which contains about 91 % RDX.
Reach truck – It is a narrow-aisle, right-angle stacking truck which is designed for unit load handling with rack interface. These lift trucks are meant to operate in narrow aisles and are best for storing and retrieving pallets in racks. They are engineered with two outer legs which help distribute the load weight, and a single set of wheels in the back.
Reactance – In electrical circuits, reactance is the opposition presented to alternating current by inductance and capacitance. Along with resistance, it is one of two elements of impedance. However, while both elements involve transfer of electrical energy, no dissipation of electrical energy as heat occurs in reactance; instead, the reactance stores energy until a quarter-cycle later when the energy is returned to the circuit. Greater reactance gives smaller current for the same applied voltage. Reactance is used to compute amplitude and phase changes of sinusoidal alternating current going through a circuit element. Like resistance, reactance is measured in ohms, with positive values indicating inductive reactance and negative indicating capacitive reactance. It is denoted by the symbol X’X’. An ideal resistor has zero reactance, whereas ideal reactors have no shunt conductance and no series resistance. As frequency increases, inductive reactance increases and capacitive reactance decreases.
Reactant – It is a substance which is consumed in the course of a chemical reaction. It is sometimes used interchangeably with reagent.
Reactant concentration – It refers to the quantity of a reactant substance present in a given volume of a chemical reaction, frequently expressed in moles per litre (molarity or M). A higher concentration means there are more reactant particles, leading to a higher frequency of collisions and, consequently, an increased rate of reaction.
Reacting fuel – It is a substance which reacts with an oxidizing agent, very frequently oxygen, in a chemical process called combustion, to release energy in the form of heat and light. This reaction, also known as burning, needs the presence of the fuel, an oxidizer, and heat to occur and is an essential process for generating power in vehicles, homes, and industries.
Reacting system – It is a collection of chemical reactants and products where chemical reactions occur, frequently involving multiple phases and influenced by concentration and temperature.
Reaction – It is a process which leads to the chemical transformation of one set of chemical substances to another. It is a chemical transformation or change brought about by the interaction of two substances. In the context of beams, reaction refers to the support forces and moments which counteract the applied loads on a beam, ensuring it remains stable and balanced. These reactions, which occur at the beam’s supports (like hinges, rollers, or fixed ends), are the structural response to the loads, and are calculated by engineers using principles of statics to design safe and effective structures.
Reaction barrier – It is the energy deficit which is to be overcome in order for a particular chemical reaction to proceed. In transition state theory, the reaction barrier is interpreted as the difference between the zero-point energy of the activated complex formed in the reaction and that of the initial reactants.
Reaction blading – This concept is used in the design of steam turbine. Here the pressure drop per stage is equally divided between fixed and moving blades. In the fixed blades steam is accelerated to a velocity only slightly higher than that of the moving blades. Continued expansion of the steam in the moving blades provides thrust and gives the steam a relative velocity equal and opposite to its former absolute velocity. In reaction blading the energy transferred to the rotor in a single stage is only around half which is transferred by impulse blading. Efficiencies, however, are comparable. It turns out that the velocity value is around twice as high for impulse blading as it is for reaction blading. This means, in turn, that an impulse turbine needs fewer stages for the same power output than a reaction turbine. However, the efficiency is about the same for both the types.
Reaction bonding – It is frequently used in materials science. It is a process where a chemical reaction, like the reaction between silicon and carbon, forms a bond between materials, typically creating a solid material or joining two materials together. Reaction bonding also refers to a process where monomeric units coalesce to form clusters through bonding reactions, leading to elongation of linear chain segments and branching. This process results in the formation of equilibrium distributions of cluster sizes with different numbers of branch points.
Reaction chamber – It is a controlled environment where chemicals or substances are mixed and undergo a specific reaction or process, frequently at high temperatures or pressures, such as a laboratory experiment. It is designed to contain and facilitate the chemical transformation, with specific features for monitoring and controlling conditions like temperature, gas atmosphere, and fluid handling.
Reaction equation – It is also called chemical equation. It is a symbolic representation of a chemical reaction, showing the reactants on the left and products on the right, separated by an arrow. A balanced reaction equation also includes coefficients which ensure the same number of atoms for each element on both sides of the equation, representing the mole relationships between reactants and products according to the law of conservation of matter.
Reaction flux – It is a flux composition in which one or more of the ingredients reacts with a base metal upon heating to deposit one or more metals.
Reaction injection moulding (RIM) – It is a process for moulding polyurethane, epoxy, and other liquid chemical systems. Mixing of two to four components in the proper chemical ratio is accomplished by a high-pressure impingement-type mixing head, from which the mixed material is delivered into the mould at low pressure, where it reacts (cures). It is also known as structural reaction injection moulding.
Reaction kinetics – It is concerned with understanding the rates of chemical reactions. It is different from chemical thermodynamics, which deals with the direction in which a reaction occurs but in itself tells nothing about its rate. Reaction kinetics includes investigations of how experimental conditions influence the speed of a chemical reaction and yield information about the reaction’s mechanism and transition states, as well as the construction of mathematical models which also can describe the characteristics of a chemical reaction.
Reaction mechanism – It consists of the step-by-step sequence of elementary reactions by which a larger chemical reaction or overall change occurs. A complete mechanism is to describe and explain which bonds are broken and which are formed (and in what order), as well as all reactants, products, and catalysts involved; the quantities of each; all intermediates, activated complexes, and transition states; and the stereochemistry of each chemical species. Since the detailed processes of a complex reaction are not observable in majority of the cases, a reaction mechanism is frequently a theoretical conjecture based on thermodynamic feasibility and what little support can be gained from experiment.
Reaction medium – It is the environment in which a chemical reaction occurs, influenced by the nature of the solvent and the presence of chains which can modify its properties, such as polarity and dielectric constant.
Reaction rate – It is the speed at which reactants are converted into products in a chemical reaction.
Reaction rate constant – It is also called reaction rate coefficient. It is a proportionality constant which quantifies the rate and direction of a chemical reaction by relating it with the concentration of reactants.
Reaction sequence – It is a series of chemical reactions which occur in a specific, consecutive order, where the product of one reaction serves as the reactant for the next, ultimately transforming reactants into final products. This detailed pathway, also known as a reaction mechanism or reaction step. It explains the step-by-step process of a complex chemical reaction
Reaction sintering – It can be defined as a fabrication process in which two or more components of the required compound react together during the sintering operation. It is the sintering of a metal powder mixture consisting of at least two components which chemically react during the treatment. It is a process at a certain temperature when the powder compact is synthesized through the chemical reaction among solid phase, liquid phase, and gas phase, and sintering densification is completed.
Reaction stoichiometry – It is the study of the quantitative relationships between reactants and products in a chemical reaction, using balanced chemical equations to calculate the quantities of substances involved. It determines the precise quantities of reactants needed or the quantities of products formed in a chemical process, relying on the ‘law of conservation of mass’ for ensuring that matter is neither created nor destroyed during the reaction.
Reaction stress – It is a stress which cannot exist in a member if the member is isolated as a free body without connection to other parts of the structure.
Reaction temperature – It is the specific temperature at which a chemical reaction occurs, or is carried out, and considerably influences the reaction’s rate and outcome. Higher temperatures normally increase the speed of a reaction by providing more energy for effective molecular collisions, while specific temperatures are frequently used to control reaction pathways or favour the formation of desired products.
Reaction thermodynamics – It studies the energy changes associated with chemical reactions, focusing on the flow of energy and the relationship between heat, work, and changes in the state of matter. It helps determine the extent of a reaction and the conditions for equilibrium, but unlike chemical kinetics, it does not concern itself with the speed at which a reaction occurs.
Reaction turbine – In the reaction turbine, the rotor blades themselves are arranged to form convergent nozzles. This type of turbine makes use of the reaction force produced as the steam accelerates through the nozzles formed by the rotor. Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the stator as a jet which fills the entire circumference of the rotor. The steam then changes direction and increases its speed relative to the speed of the blades. A pressure drop occurs across both the stator and the rotor, with steam accelerating through the stator and decelerating through the rotor, with no net change in steam velocity across the stage but with a decrease in both pressure and temperature, reflecting the work performed in the driving of the rotor. In the reaction turbine, the fixed blades and the moving blades which constitute one stage are practically identical in design and function, each accounting for about half of the pressure-drop which is converted to kinetic energy in the entire stage. In the fixed blades, the pressure is harnessed to increase the velocity of the steam so that it slightly exceeds the velocity of the moving blades in the direction of rotation. In the moving blades, the pressure drop is again used to accelerate the steam but at the same time to turn it around (with respect to the blades), so that its absolute tangential velocity is almost zero as it enters the next bank of stationary blades. Hence, thrust is imparted to the moving blades as the absolute tangential velocity of the steam is reduced from slightly above blade speed to around zero. An imaginary observer moving with the steam cannot tell whether he is passing through the fixed blades or the moving ones. As he approaches either type of blade, it appears to be nearly motionless, but as he travels in the channel between blades, his velocity increases steadily until he reaches their trailing edges, which then seems to be receding rapidly.
Reaction velocity – It is also called reaction rate. It is the speed at which a chemical reaction occurs, defined as the change in concentration of reactants or products over a unit of time. It quantifies how quickly reactants are consumed or products are formed. This rate is typically measured in units of molarity per second or moles per unit time, and it is influenced by factors like temperature, reactant concentration, and the presence of a catalyst.
Reaction vessel – It is a closed container where chemical reactions are performed under controlled conditions, allowing for precise manipulation of temperature, pressure, and mixing to produce desired chemical products. These vessels can range in size from small laboratory units to large industrial tanks and are made from materials like glass or different grades of stainless steel.
Reaction zone – It is a specific region where substantial chemical or physical transformations occur, It is frequently characterized by high temperatures, active sites, or increased mass and heat fluxes which promote chemical reactions. Examples include the emulsion of metal, gas, and slag in a basic oxygen furnace, or the combustion zone in a gasifier where fuel burns rapidly.
Reactivation – It is the act or process of making something active again or becoming active again. It is the act or process of reactivating or the condition of being reactivated.
Reactive bond – It is a chemical bond between atoms which, in a particular context, is relatively unstable and hence easily broken or invaded by other chemical species or radicals, e.g., the double bond in ethylene (CH2=CH2) is highly reactive in the presence of other ethylene molecules, leading to a polymerization reaction which forms polyethylene.
Reactive bonding – It is a wafer bonding procedure which uses highly reactive nano-scale multi-layer systems as an intermediate layer between the bonding substrates. The multi-layer system consists of two alternating different thin metallic films. The self-propagating exothermic reaction within the multi-layer system contributes the local heat to bond the solder films. Based on the limited temperature the substrate material is exposed, temperature-sensitive components and materials with different coefficient of thermal expansions, i.e., metals, polymers and ceramics, can be used without thermal damage.
Reactive distillation (RD) – It is a single-vessel process which combines a chemical reaction and a distillation separation in one unit, aiming to improve efficiency, reduce costs, and improve conversion rates. It integrates a catalytic reaction (frequently in the presence of heterogeneous catalysts) within a distillation column, allowing for the continuous removal of reaction products by vapourization. This process is particularly effective for reversible reactions where continuous product removal shifts the equilibrium, leading to higher conversion than conventional processes.
Reactive evaporation – It is a vacuum deposition process in which trace quantities of an active gas are added to the vacuum chamber. The gas reacts with an evaporating material in the chamber, promoting deposition of the material on a substrate.
Reactive hydroxyl group – It is an -OH (oxygen-hydrogen) functional group which can readily participate in chemical reactions, such as alkylation, forming new bonds and allowing for substitution or conjugation with other molecules. Reactive hydroxyl groups are important since their presence enables molecules to link together, modify surfaces, or act as sites for further chemical modifications.
Reactive intermediate – It is a short-lived, unstable, highly reactive chemical species which is generated briefly in a chemical reaction but rapidly undergoes further reactions which transform it into a more stable species. It is hence a transient intermediary between the stable reactants and products of the overall reaction. The existence of intermediates, when detectable, is critical to an accurate understanding of a reaction mechanism.
Reactive ion-beam assisted deposition (RIBAD) – It is a thin-film deposition technique which combines physical vapour deposition (PVD) with ion bombardment, where a reactive gas is used to feed the ion source. It is a combination of two surface treatment processes, namely, vacuum deposition and ion implantation in which a reactive gas is used to feed the ion source. The deposition process is normally accountable for the material build-up, while the ion flux imparts the kinetic energy required to achieve adhesion and the needed coating properties. This process improves film properties like adhesion and density.
Reactive ion plating – It is a type of physical vapour deposition (PVD) where a reactive gas or vapour is introduced into the plasma, allowing for the deposition of compound materials by bombarding the substrate with energetic particles and reacting them with the depositing material.
Reactive maintenance – It is also known as breakdown maintenance or run-to failure maintenance. It basically consists of running the equipment till a breakdown takes place. No actions are taken or efforts are made to maintain the equipment till the failure of the equipment. In this type of maintenance strategy, the maintenance action is taken up when the equipment breaks down completely and needs repair to resume operation. Sometimes breakdown maintenance is the default maintenance strategy, relying on reactive maintenance. The reactive maintenance strategy is preferable where repair of the equipment is simple and easier, and where preventive maintenance carried out in stopping or disrupting normal production runs is very costly. Under the reactive maintenance strategy approach, there is no expenditure on maintenance manpower nor on cost of spares and consumables till there is a breakdown of the equipment. However, a large expenditure is needed when there is a breakdown in the equipment both in terms of manpower costs and capital costs. This approach can result into secondary equipment or process damage from equipment failure. Also, longer shutdown is needed for repair which affects the production. Unplanned shutdown of the equipment because of the failure disturbs the production planning. All these affect the supply of the products to the customers. With this type of maintenance approach, the life of the equipment gets shortened resulting in more frequent replacement. Further since the equipment is run to failure, a large material inventory of repair parts is needed to be maintained.
Reactive materials – These are substances which readily undergo chemical changes, frequently violently, when exposed to certain conditions like heat, pressure, shock, friction, air, or water, potentially leading to hazardous reactions like explosions or fires.
Reactive medium – It is a substance or system which undergoes a change or transformation when interacting with something else, such as a contaminant, a stimulus, or a particle. In environmental contexts, it can be a material placed in the subsurface to chemically transform pollutants. In other fields, it can be a medium which absorbs or reacts to incoming particles, or even a component of a reactive system that generates energy or pressure upon initiation.
Reactive membrane – It is a separation membrane designed to perform chemical reactions within or on its surface, coupling filtration with chemical processes like catalysis, oxidation, or adsorption to remove pollutants or transform substances. Unlike conventional ‘passive’ membranes, reactive membranes are functionalized with active sites or integrated with catalytic materials to improve separation efficiency, reduce energy consumption, and prevent membrane fouling.
Reactive metal – It is a metal which readily combines with oxygen at elevated temperatures to form very stable oxides, for example, titanium, zirconium, and beryllium. Reactive metals can also become embrittled by the interstitial absorption of oxygen, hydrogen, and nitrogen.
Reactive power – It is that component of apparent power which flow because of the return to the source of energy stored in a load’s electric or magnetic fields, which does no useful work at the load.
Reactive process – It is a process characterized by reactions, where substances chemically change, combine, or interact to form new substances, frequently with energy changes. These processes can occur in different fields, and can range from simple oxidation reactions to complex polymer moulding. In a broader sense, it can also refer to systems or approaches which respond to events or inputs rather than initiating action, such as in reactive programming or reactive quality assurance.
Reactive sputtering – It is the sputtering of elemental targets in the presence of chemically reactive gases which react with both the vapour flux ejected from the target and the target surface. It is a physical vapour deposition (PVD) technique where a reactive gas (like oxygen or nitrogen) is introduced during the sputtering process, causing the sputtered atoms to react and form a compound film on the substrate.
Reactive steel – The term is used for some grades of steel which react more quickly with molten zinc. This is normally caused by steel chemistry, particularly silicon and phosphorous content.
Reactivity – It is the tendency of a particular chemical substance to undergo a chemical reaction, either by itself or with other substances, normally referring to either or both of two distinct observations namely (i) whether or not a substance reacts under a specific set of circumstances, and how quickly it reacts (i.e., the reaction rate). Thermodynamically, a chemical reaction occurs since the products (taken as a group) exist at a lower free energy than the reactants, and hence are more energetically ‘stable’, but the concept of reactivity can also embody kinetic factors, depending on the usage. Chemical stability and stability and chemical compatibility are related but distinct concepts.
Reactivity controlled compression ignition (RCCI) – It is a combustion process in diesel engines which utilizes two fuels with opposite reactivity characteristics (low reactivity fuel, such as alcohols, and high reactivity fuel, such as vegetable oils) to create reactivity stratification in the combustion chamber, resulting in improved performance and reduced smoke and ‘no’ emissions.
Reactivity series It is also called activity series. It is an empirical, calculated, and structurally analytical progression of a series of metals, arranged by their general reactivity from highest to lowest and used to summarize information about their reactions with acids and water and the methods used to extract them from ores.
Reactor bed – It is a chamber within a reactor vessel containing solid material, such as catalyst particles or feedstock, through which a fluid (liquid or gas) flows to facilitate a chemical or biological reaction. Common types include fixed beds, where the solid remains stationary, fluidized beds, where solids are suspended in the fluid like a fluid, and moving beds, where the solids are continuously circulated.
Reactor, chemical – The reactor is an apparatus / vessel in which chemical operations are carried out for pilot or industry purposes. The reactors change in scale from a small unit to the massive structures. Reactors are designed based on several factors, but the most important factors are the kinetics and thermodynamics. Reactors are one of the main parts of any industrial process since the conversion of crude substrates into invaluable chemicals is performed in the reactors. Reactor design has received much attention in the past because of the significant energy involved.
Reactor containment – It is a reinforced, gas-tight structure enclosing a nuclear reactor designed to be the final barrier in a defense-in-depth strategy, preventing the escape of radioactive materials into the environment during normal operation and accidents, and protecting the reactor from external hazards. Typically, it is made of steel-reinforced concrete, the containment also provides radiation shielding.
Reactor coolant system – It is the system which is used to remove energy from the reactor core and transfer that energy either directly or indirectly to the steam turbine.
Reactor core – It is the central component of a nuclear reactor where controlled nuclear fission occurs, generating heat from nuclear fuel. It houses fuel assemblies containing fissionable material, surrounded by a coolant to absorb heat, and a moderator to slow fission-produced neutrons to sustain the chain reaction. Control rods are also integrated to manage the rate of fission.
Reactor, electrical – It refers to an inductor, or a coil, used to introduce reactance into an alternating current circuit, primarily to control current flow and improve power system stability. It is also known as a line reactor. It is a coil wired in series between two points in a power system to minimize inrush current, voltage notching effects, and voltage spikes. Reactors can be tapped so that the voltage across them can be changed to compensate for a change in the load that the motor is starting. Reactors are rated by the ohms of impedance that they provide at a given frequency and current. Reactors can also be rated by the I2R (square of current multiplied by resistance) loss across the device at a certain frequency at a rated current. Two common types of reactors are the dry-type and the oil-immersed. The dry-type is open and relies on the air to circulate and dissipate the heat. Dry-type reactors are common in low-voltage applications. Oil-immersed reactors are common in high-voltage applications. Oil-immersed reactors are placed in tanks and require a magnetic shield to prevent eddy currents from circulating in the tank. The shield is made from laminated steel sheets like the transformer core and motor stators. Reactors may be used as line or load reactors. Line reactors are used when low line impedance allows high inrush current, when power factor correction capacitors are used, or when a motor drive causes notching.
Reactor kinetics – It is the study of how the power level and neutron flux of a nuclear reactor change over time in response to different inputs, or reactivity changes, such as control rod movements or reactivity insertions. It analyzes short-term, time-dependent behaviours, differentiating between steady-state (constant power) and transient (changing power) conditions, and is important for understanding and designing reactor control systems and ensuring safe operations.
Reactor pressure vessel – It is the part of the nuclear power plant which houses the reactor core and the cooling system. It is the thick-walled, primary steel containment which houses the nuclear reactor core and coolant, acting as the most critical safety boundary in a nuclear power plant to prevent the release of radioactive materials. These large, cylindrical vessels are designed to withstand extremely high pressures, temperatures, and neutron irradiation, requiring high reliability and specific structural integrity measures, such as conservative margins of fracture toughness and special steel materials to resist radiation embrittlement over their lifetime.
Reactor protection system – It is a set of highly reliable, redundant systems in a nuclear reactor designed to automatically and manually trigger a reactor shutdown (scram) to prevent damage to the reactor core and control radioactive material release. It monitors critical parameters like power, temperature, and pressure, and initiates a full insertion of control rods when these limits are approached or exceeded, ensuring core integrity and safety.
Reactor safety – It is the practice of implementing engineering designs and operational protocols to prevent accidents and the release of radioactive materials, hence protecting workers, the public, and the environment from radiation hazards. It involves the ‘defense-in-depth’ approach, which uses inherent design features and multiple redundant safety systems to achieve safe reactor operation throughout its entire lifecycle, from design and construction to decommissioning.
Reactor vendor – It is an organization which deals with reactor and reactor design.
Readiness review – It is a final review of an engineered system from the viewpoint of readiness for safe operation. All critical personnel are brought together and all safety hazards are reexamined to see whether the hazards have been adequately addressed. Operating procedures are assessed to ensure that personnel are properly trained, not only for normal operation, but also for emergency situations.
Readout circuit – It is the electronic system designed to interface with a sensor (like an accelerometer, detector, or gas sensor), collect the signals it generates, and convert them into a usable data format, frequently through amplification and analog-to-digital conversion (ADC). These circuits are important in different applications, from imaging systems which use sensor arrays to simpler sensors, ensuring the collected signals are amplified, filtered, and accurately processed for analysis or display. A ‘readout integrated circuit (ROIC) is a specialized type of readout circuit which integrates these functions onto a single micro-electronic chip.
Reagent – It is another name for a reactant. It is a substance or compound which added to a system to cause a chemical reaction. It is a test substance which is added to a system in order to bring about a chemical reaction, or to see whether a reaction occurs.
Reagent chemicals – These are high-purity chemicals which are used for analytical reactions, for testing of new reactions where the effects of impurities are unknown, and for chemical work where impurities are either to be absent or at a known concentration.
Real area of contact – It is also known as actual contact area. In tribology, it is the total area of contact formed by summing the localized asperity contact areas within the apparent area of contact.
Real component – It refers to the part of a complex number which represents the in-phase component, such as the current flowing through a resistor, in contrast to the imaginary component which accounts for out-of-phase behaviour because of its reactive loads.
Real contact area – It is the actual, physical area of contact between two surfaces, composed of the sum of all microscopic contact points (asperities) at the atomic level, which is frequently a tiny fraction of the larger, apparent contact area visible at a macro-scopic scale. This area is a key factor in tribological phenomena such as friction and wear, as it determines the intensity of contact between the surfaces.
Real contact surface – It refers to the microscopic interface where actual physical contact occurs between two surfaces, typically consisting of a network of tiny, rough points called asperities. This ‘real’ area of contact is normally a tiny fraction of the much larger ‘apparent’ or ‘nominal’ contact area and is where forces are transmitted, influencing properties like friction and wear.
Real crystal – It is a solid material with atoms, molecules, or ions arranged in a highly ordered, repeating, three-dimensional pattern known as a crystal lattice. This internal structure results in macro-scopic shapes with specific geometric properties and unique optical, electrical, and mechanical characteristics that differentiate them from amorphous solids like glass or polycrystalline materials.
Real density – It is the intrinsic density of a solid material, calculated as its mass divided by the volume of the material itself, excluding all internal pores and voids. It is also called true density. It represents the density of the solid matter, without any contribution from open or closed pores within the material or interstitial spaces between particles. Real density is measured using methods like gas displacement pycnometry, which uses a gas (frequently helium) to determine the true volume of the solid material. In case of powders, it is the density of the solid phase in powder particles, calculated based on the specific weight of the constituents, such as lead oxide and free lead, without considering the volume of any pores.
Real fluid – It is a fluid which has finite viscosity, meaning it shows internal friction during flow, in contrast to an ideal fluid, which is hypothetical and has zero viscosity.
Real gas – It is a gas which does not perfectly obey the gas laws because of the presence of molecular volume and forces of attraction and repulsion between its molecules. As gases are compressed or cooled, their behaviour increasingly deviates from that of an ideal gas.
Real gas law – It refers to an equation which accounts for deviations from ideal gas behaviour under conditions of high pressure and low temperature, incorporating additional terms to correlate calculated values with observed gas behaviour.
Real leak – It is a crack, crevice, fissure, hole or passage way in the wall of an enclosure, capable of passing air, or other gases, from one side of the wall to the other under an action of a pressure or concentration differential existing across the wall.
Real network – It is an actual operational network characterized by its physical parameters and network effects, as opposed to a simulated environment. It presents challenges for testing machine learning methods due to security and privacy concerns, leading to a reality gap between simulation and real-world performance.
Real time analyzer – It is an instrument which processes signals through an array of parallel filters, allowing for the immediate analysis of frequency components in the Doppler-shift signals. It produces output that can be recorded with variable density, facilitating the visualization of signal characteristics in real-time.
Real-time computing (RTC) – It is the computer science term which is used for hardware and software systems subject to a ‘real-time constraint’, e.g., from event to system response. Real-time programs must guarantee response within specified time constraints, often referred to as ‘deadlines’. The term ‘real-time’ is also used in simulation to mean that the simulation’s clock runs at the same speed as a real clock. Real-time responses are frequently understood to be in the order of milli-seconds, and sometimes micro-seconds. A system not specified as operating in real time cannot normally guarantee a response within any time-frame, although typical or expected response times can be given. Real-time processing fails if not completed within a specified deadline relative to an event. Deadlines are always to be met, regardless of system load.
Real-time control system (RCS) – It is a system in which the correctness of a result depends not only on its logical accuracy but also on the time interval in which the result is delivered. It is to meet criteria such as reliable operation execution, determined operation deadlines, and predictable operation results to ensure stability and repeatability in control operations.
Real-time data (RTD) – It is information which is delivered immediately after collection. There is no delay in the timeliness of the information provided. Such data is normally processed using real-time computing although it can also be stored for later or off-line data analysis. Real-time data is not the same as dynamic data. It can be dynamic (e.g., a variable indicating current location) or static (e.g., a fresh log entry indicating location at a specific time).
Real-time data visualization – It is the process of visually representing data as it is generated and processed, allowing users to monitor and analyze data instantly, enabling quick decision-making and trend identification.
Real-time operating system (RTOS) – It is an operating system (OS) for real-time computing applications which processes data and events which have critically defined time constraints. A real-time operating system is distinct from a time-sharing operating system, such as Unix, which manages the sharing of system resources with a scheduler, data buffers, or fixed task prioritization in multi-tasking or multi-programming environments. All operations are to verifiably complete within given time and resource constraints or else fail safe. Real-time operating systems are event-driven and preemptive, meaning the operating system can monitor the relevant priority of competing tasks, and make changes to the task priority. Event-driven systems switch between tasks based on their priorities, while time-sharing systems switch the task based on clock interrupts.
Real-time optimization (RTO) – It is a model-based method that continuously analyzes data and adjusts process variables to achieve optimal economic and operational performance, even with disturbances and changing conditions. It uses advanced control systems, algorithms, and software to set optimal setpoints for process operations, maximizing performance by balancing multiple variables and constraints to minimize costs and satisfy objectives.
Real-time process monitoring – It is the continuous tracking, analysis, and reporting of data from systems, equipment, or processes as they are happening, with minimal delay between data collection and action. It uses sensors, software, and communication networks to provide instant, up-to-date information, allowing for immediate detection of issues, rapid decision-making, and timely corrective actions to maintain efficiency, quality, and performance.
Real-time radiography – A method of nondestructive inspection in which a two-dimensional radiographic image can be immediately displayed on a viewing screen or television monitor. This technique does not involve the creation of a latent image; instead, the unabsorbed radiation is converted into an optical or electronic signal, which can be viewed immediately or can be processed in near real time with electronic and video equipment.
Real-time system – It has been described as one which ‘controls an environment by receiving data, processing them, and returning the results sufficiently quickly to affect the environment at that time’. The term ‘real-time’ is used in process control and enterprise systems to mean ‘without significant delay’.
Reamer – It is a rotary cutting tool with one or more cutting elements (teeth), used for enlarging a hole to desired size and contour. It is supported principally by the metal around the hole it cuts.
Reaming – It is an operation in which a previously formed hole is sized and contoured accurately by using a rotary cutting tool (reamer) with one or more cutting elements (teeth). The principal support for the reamer during the cutting action is obtained from the work-piece.
Reaming shell – It is a component of a string of rods which is used in diamond drilling. It is set with diamonds and placed between the bit and the core barrel to maintain the gauge (or diameter) of the hole.
Rear-end condition – It is a condition which is occurring in the last metal to be extruded. It is a result of the oxidized surface of the billet feeding into the extrusion.
Rear view – It is directly opposite to the front view and is at the back of the object.
Rear axle – It is the principal driven axle located at the rear of a vehicle, which transmits power from the engine to the wheels, frequently involving a propeller shaft connected to the transmission.
Rear suspension – It is a system which connects the rear axle to the vehicle body, allowing for vertical movement of the axle while preventing longitudinal and lateral misalignment because of the different forces, such as braking and crosswinds. It typically includes components like coil springs, trailing arms, and anti-roll mechanisms to maintain wheel alignment and stability during operation.
Rear-wheel drive (RWD) – It is a form of engine and transmission layout used in motor vehicles, in which the engine drives the rear wheels only. Majority of the rear-wheel drive vehicles feature a longitudinally-mounted engine at the front of the vehicle.
Reasonable expectations – It is based on high level of confidence. This term is used within the E1 classification and concerns the likelihood that all necessary conditions will be met. It is also used in the F1.3 Sub-category and concerns the likelihood that all necessary approvals / contracts for the project to proceed to development will be forthcoming.
Reasonable prospects – It is based on moderate level of confidence. This term is used within the E2 and E3 classification and concerns the likelihood that all necessary conditions will be met.
Reasonable time frame – It is the Time frame within which all approvals, permits and contracts necessary to implement the project are to be obtained. This is to be the time normally accepted as the typical period required to complete the task or activity under normal or typical circumstances.
Reasonably available control technology (RACT) – It is the control technology which that is reasonably available, and both technologically and economically feasible. It is normally applied to existing sources in non-attainment areas. In majority of the case, It is less stringent than new source performance standards.
Reasoning process – It is the mental activity of using existing knowledge, facts, or evidence to draw conclusions, make decisions, solve problems, or construct explanations. It involves a step-by-step approach to thinking, applying logic and rational appraisal of information to move from premises to a coherent outcome, such as a conclusion, prediction, or justification. This process is fundamental to human thought and can be seen in everyday decision-making as well as in formal fields like logic, mathematics, and artificial intelligence.
Re-association – it is the recombination of the products of dissociation.
Rebar – It is short for reinforcement bar. It is a steel bar used to improve the tensile strength of concrete structures. Concrete is strong in compression but weak in tension, and rebar compensates for this weakness, preventing cracks and improving the overall load-bearing capacity, stability, and longevity of buildings, bridges, and other constructions. The bars are typically ribbed to improve bonding with the concrete, and they come in different sizes, grades, and types to meet specific project requirements.
Rebar corrosion – It is the electro-chemical degradation of steel reinforcement bars (rebar) embedded in concrete, mainly caused by environmental factors like chloride ingress and carbonation which break down concrete’s protective alkaline layer. This process results in rust formation, which expands and creates internal pressure, leading to cracks, spalling, reduced structural strength, and decreased load-bearing capacity in reinforced concrete structures.
Re-blending – It means to mix or combine something again, or to blend something which has already been blended.
Reboiler – It is a type of heat exchanger which provides heat to the bottom of a distillation column to vapourize a portion of the liquid. This generated vapour rises through the column, enabling the separation of components based on their different volatilities, while the remaining liquid is withdrawn as the bottom product. Reboilers use different heating media, such as steam, to achieve this partial vapourization, and they come in different types, including kettle and thermosyphon designs.
Reboiler tube – It is a specialized component within a reboiler, which is a heat exchanger designed to partially vapourize the liquid stream from the bottom of a distillation column to generate the vapour needed for the separation process. These tubes are engineered for efficient heat transfer from a heating medium (like steam) to the liquid, facilitating the crucial step of boiling and creating the vapour that travels up the column.
Reboiling – In porcelain enamel, it is the gas evolution occurring and recurring during repeated firing of the ground coat. It is sometimes considered a defect.
Rebonded fused grain refractory – It is a fired refractory brick or shape made predominantly or entirely from fused grain.
Rebonding – It is the term normally used in reference to adding new bonding material to used moulding sand so that it can be used again to produce moulds.
Rebound – It is the gunned material which is not adhering to the gunned or shotcreted surface during the gunning process.
Rebound hammer – It is also called Schmidt hammer. It is a non-destructive testing (NDT) device which measures the surface hardness and penetration resistance of concrete or rock by quantifying the rebound of a spring-loaded mass after impact. The rebound value, or rebound number, is recorded on a graduated scale and used to assess the quality and uniformity of concrete in-situ, providing an estimated indication of its compressive strength when correlated with conversion charts.
Rebound hammer test – It is a non-destructive method used to estimate the in-situ compressive strength and surface hardness of hardened concrete and rock. It operates on the principle that a spring-controlled mass, upon striking a concrete surface, rebounds to an extent which is directly related to the surface’s hardness, which in turn correlates to its compressive strength. The rebound value, or rebound number, is read on a graduated scale and converted to a strength value using established correlation charts or graphs.
Recalescence – It is the increase in temperature which occurs after undercooling, since the rate of liberation of heat during transformation of a material exceeds the rate of dissipation of heat. It is also a phenomenon, associated with the transformation of iron to iron on cooling (super-cooling) of iron or steel, which is revealed by the brightening (re-glowing) of the metal surface owing to the sudden increase in temperature caused by the fast liberation of the latent heat of transformation.
Recalibration – It is the process of re-adjusting a device, instrument, or system after it has been calibrated initially to restore its accuracy and ensure it continues to meet performance standards over time. This fine-tuning is necessary since components can degrade, drift, or be affected by environmental changes, leading to inaccurate measurements or operation. Recalibration ensures reliability, precision, and the ability to meet regulatory and quality requirements.
Recarburize – It is carried out to increase the carbon content of molten cast iron or steel by adding carbonaceous material, high-carbon pig iron, or a high-carbon alloy. It also means to carburize a metal part to return surface carbon lost in processing It is also known as carbon restoration.
Recarburizing – It means increasing the carbon content of molten cast iron or steel by adding carbonaceous material, high-carbon pig iron, or a high-carbon alloy. It is also carburizing a metal part to return surface carbon lost in processing.
Receiver – It is the apparatus which takes radio-frequency currents induced in an antenna and turns them into useful signals. In pneumatics, a ‘receiver’ is a pressure vessel which stores compressed air, acting as a buffer between the compressor and the fluctuating demand of pneumatic equipment, ensuring a steady air supply.
Receiver operating characteristic (ROC) – It is a graph which visualizes the performance of a binary classification system across all possible thresholds by plotting the true positive rate (sensitivity) against the false positive rate (1-specificity). It helps assess how well a diagnostic test or model can distinguish between two classes by showing the trade-off between correctly identifying positive cases and incorrectly identifying negative cases as positive at different cut-off points.
Receiving ladle – It is a ladle placed in front of the melting furnace into which all metal is tapped. It acts as a mixer and reservoir and to smooth out metal flow to the pouring area.
Recess – It is a groove or depression in a surface.
Recharge – It is the process by which water is added to a zone of saturation, normally by
percolation from the soil surface, like the recharge to an aquifer.
Rechargeable battery – It is a battery which can have a useful portion of its capacity restored by connection to a supply of electric current.
Rechucking – It means reversing a pattern upon a face plate to permit turning the opposite face to the required shape.
Reciprocal displacement – It refers to the displacement at a point in a linearly elastic body caused by loads applied at different points, expressed as the sum of individual contributions from each load, where each contribution is determined by flexibility coefficients that describe the relationship between the displacement and load.
Reciprocal lattice – It is a lattice of points, each representing a set of planes in the crystal lattice, so that a vector from the origin of the reciprocal lattice to any point is normal to the crystal planes represented by that point and has a length that is the reciprocal of the plane spacing.
Reciprocal lattice point – It is a point in reciprocal space, a mathematical space derived from a crystal’s real-space lattice, which corresponds to a family of parallel lattice planes in the crystal. The distance of a reciprocal lattice point from the origin is the inverse of the interplanar spacing (1/d) of the corresponding family of planes, and the direction to the point is perpendicular to these planes. Reciprocal lattice points are necessary in understanding crystal diffraction patterns, as the positions of diffraction spots directly relate to the reciprocal lattice.
Reciprocal linear dispersion – It is the derivative dL/dx, where ’L’ the wavelength and ‘x’ is the distance along the spectrum. The reciprocal linear dispersion normally is expressed in Angstrom per millimeter.
Reciprocal network – It is typically a linear passive two-port network. It is one where the transfer function of signal or energy between two ports is the same regardless of the direction of transmission. For example, if one applies a current at port 1 and measures the voltage at port 2, the ratio of voltage to current is the same as if one applies the same current at port 2 and measures the voltage at port 1. This symmetry in transmission characteristics is verified by specific mathematical conditions depending on the network parameters used, such as Z12 = Z21 for impedance (Z) parameters and Y12 = Y21 for admittance (Y) parameters.
Reciprocating compressor – It is a positive-displacement machine which uses a piston to compress a gas and deliver it at high pressure.
Reciprocating feeder – The feeder has reciprocating tray. The reciprocating motion is imparted by crank or eccentric and connecting rod. The feeder discharge is volumetric in nature, and is less susceptible to flowability of material, as compared to vibrating feeder. However, material movement on tray is of simple dragging nature, instead of jumping type as in case of vibrating feeder. This results into more wear of tray. The magnitude of vibrating forces is comparatively high but at a very low frequency (e.g. about 60 cycle per minute). The commonly used reciprocating feeders have capacity range up to 250 cubic meter per hour, for material of average abrasiveness. The higher capacities are possible. The feeder can handle larger lumps compared to the vibrating feeders.
Reciprocating pin-on-flat test – It is also known as tribometer. It, is a method which is used to study friction and wear, where a pin (or ball) moves back and forth (reciprocates) against a stationary flat surface, allowing people to assess the wear and friction characteristics of materials.
Reciprocating pump – It is a type of positive displacement pump that uses a piston, plunger, or diaphragm moving in a back-and-forth (reciprocating) motion to displace fluid, creating a constant volume flow suitable for low-flow, high-pressure applications.
Reciprocating rake bar screens – These are essentially automated bar screens which utilize a single rake to clean a stationary bar rack. The rake, attached to a reciprocating mechanism, moves back and forth across the bar rack, efficiently removing accumulated debris.
Reciprocating screen – It is a type of screening equipment which uses a back-and-forth, or reciprocating, motion to separate materials based on size. It is frequently used in industries like waste-water treatment and mining.
Reciprocating wear tests – These tests simulate real-world mechanical interactions by subjecting materials to repetitive back-and-forth motion. These tests provide crucial insights into friction, material degradation, and durability under cyclic loading conditions, helping engineers understand and improve component performance. Different test configurations, including pin-on-flat, ball-on-flat, and cylinder-on-flat, allow people to study different contact geometries and wear mechanisms. By controlling parameters like load, stroke length, and frequency, these tests reveal how materials behave under specific operating conditions.
Reciprocity – In electrical networks, it is a theorem which states that the current injected into one point in a network produces a voltage at a second point which is identical to the voltage produced at the first point by injection of the same current at the first point. In electro-magnetism, reciprocity is an observation which electric currents and electric fields can be analyzed from either point of view as regards the source of the energy in the system, e.g., in radio, a good transmitting antenna is normally also a good receiving antenna.
Reciprocity principle – It is a relationship between two solutions in a medium where the sources and field receivers are interchanged, applicable to both static displacements and vibrating bodies, and includes the effects of dissipative forces.
Recirculating loop – It is a system where fluids, gases, or light signals are sent back to the beginning of the system for reuse, frequently to simulate long distances, enhance efficiency, or maintain performance. These loops are used in several fields, including testing fibre optic communication systems by repeated cycling of light signals, or in plumbing to provide immediate hot water by circulating it continuously to the furthest fixtures.
Recirculating systems – When working with thicker material and cold rolled and hot rolled steel (especially with scale), the recirculating system of applying lubricant is normally the best approach. Here, sufficient amounts of lubricant not only have to protect the metal working tools, but the scale and metal fines which are generated by the process are to be flushed off the tooling and into the reservoir. The use of baffles, settling tanks and filters help collect large quantities of contaminants and metal fines, helping keep the coolant relatively clean. Magnets can be extremely helpful in keeping the amount of metal being recirculated down to a minimum.
Recirculation – It is the reintroduction of part of the flowing fluid to repeat the cycle of circulation.
Recirculation ratio – It is a dimensionless quantity which represents the ratio of the quantity of fluid or substance which is recirculated or returned to a system to the quantity of fresh inflow entering the system. It is a crucial design parameter, e.g., in trickling filters, where it indicates how much treated waste-water is sent back to the filter to improve the overall treatment efficiency and reduce the load on the filter.
Recirculation zone – It is a localized area within a fluid flow where the flow reverses direction, forming a separate region, frequently characterized by a vortex, that is distinct from the main flow. These zones typically arise from adverse pressure gradients or flow separation at sharp corners, such as behind a backward-facing step or around a blunt body. They can trap and release mass, influencing the overall fluid transport, and play a role in phenomena like combustion efficiency and solute transport in fractures.
Reclaimed asphalt binder – It is a material classified into two phases namely (i) available reclaimed asphalt binder, which includes liquid and softer binders that can be mobilized and blended, and (ii) unavailable reclaimed asphalt binder, which consists of absorbed and black rock binders that are not easily mobilized.
Reclaimed water – It is also called recycled water. It is treated waste-water which is cleaned and reused for non-potable purposes like industrial processes, and ground-water replenishment.
Reclaimer – It is a large machine used in bulk material handling applications. A reclaimer’s function is to recover bulk material such as ores from a stockpile. Reclaimers are volumetric machines and are rated in cubic meters per hour for capacity, which is often converted to tons per hour based on the average bulk density of the material being reclaimed. Reclaimers normally travel on a rail between stockpiles in the stockyard. There are several types of reclaimers which are available for suiting the specific needs such as buffer storage or storage for blending the material properties (material can be free flowing or sticky material), and reliability. The two types of reclaimers which are in common use are (i) scraper reclaimers, and (ii) bucket reclaimers. Each type has varied designs to suit an application. Reclaimers are normally electrically powered by means of a trailing cable.
Reclain – It is the porcelain enamel overspray which is removed from the spray booth and reconditioned for use.
Reclamation – It is the restoration of a site after mining or exploration activity is completed.
Recognition – It is the public appreciation for a person’s or group’s achievements. It is the act of showing appreciation and acknowledgement for employees for their contributions to the organization which links to the purpose, mission and values of the organization. Employee recognition can take on different forms, such as peer-to-peer recognition, manager-led recognition and leadership-led recognition. But what is critical to employee recognition success is making sure that employee reward and recognition tactics are delivered in a way which makes recognition meaningful, unified, shine through a spotlight and timely.
Recoil – It is rebound or spring back through force of impact or elasticity. This term is widely used with particular reference to automatic weapons. In this specific setting, the recoil spring is used to compensate and absorb the bullet force momentum and to convert energy into the activation of a weapon’s reloading system.
Recoiling – In case of a rolled coil, it involves rewinding a large, processed steel coil into smaller, more manageable coils, frequently for easier handling, storage, and transportation. The recoiling operation of a rolled coil is carried out in a recoiling line.
Recoil line – It is a blemish on a drawn sheet metal part caused by a slight change in metal thickness. The mark of radial line results from transfer of the blank from the die to the punch during forming, or from a reaction to the blank being pulled sharply through the draw ring.
Recompression – It refers to the process of increasing the pressure and temperature of a vapour, frequently for energy recovery, as seen in ‘mechanical vapour recompression’ (MVR) and ‘thermal vapour recompression’ (TVR) systems. This is done by compressing the low-pressure exit vapours using a mechanical compressor (like a blower) or a steam jet, allowing them to be reused as a heating medium to improve process efficiency and reduce energy consumption.
Reconnaissance – It is a preliminary survey of ground. A reconnaissance study identifies areas of enhanced mineral potential on a regional scale based primarily on results of regional geological studies, regional geological mapping, airborne and indirect methods, preliminary field inspection, as well as geological inference and extrapolation. The objective is to identify mineralized areas worthy of further investigation towards deposit identification. Estimates of quantities are only to be made if sufficient data are available and when an analogy with known deposits of similar geological character is possible, and then only within an order of magnitude.
Reconnaissance Mineral resource – It is the estimates based on regional geological studies and mapping, airborne and indirect methods, preliminary field inspections as well as geological inference and extrapolation.
Reconsideration – It refers to the process of revisiting previous analyses, comparisons, and evaluations during an examination, allowing the examiner to reassess details and insights based on ongoing scrutiny and the availability of both reports throughout the evaluation. This iterative process acknowledges the interconnectedness of different phases of examination and enables adjustments based on newly perceived information.
Reconstruction – It is the act or process of rebuilding, restoring, or recreating something which has been damaged or exists in a different form, whether it is a physical structure like a building or road, a damaged or corrupted digital signal, a theoretical concept, or even a damaged facility after a disaster. This can involve major repairs, complete rebuilding, or even fundamental changes to its quality, function, or form, as seen in architecture, image processing, and post-disaster recovery efforts.
Record – As per the ‘records management standards’ ISO 15489.1, a record is defined as ‘information created, received, and maintained as evidence and information by an organization or person, in pursuance of legal obligations or in the transaction of business.
Record drawing – It is the as-built drawing which provide a comparison between what has been built and the original plan. It is the ‘final construction issue’ drawing by the consultant team to create record of the completed project.
Recording instrument – It is a device which continuously records the variation of a measured quantity (like voltage, current, or temperature) with respect to time, frequently on a chart or dial, providing a permanent record of the measurements.
Record integrity – The integrity of a record refers to its being complete and unaltered. It is necessary that a record is to be protected against unauthorized alteration. Records management policies and procedures are to specify what additions or annotations can be made to a record after it is created, under what circumstances additions or comments can be authorized, and who is authorized to make them. Any authorized comment, addition or deletion to a record is to be explicitly indicated and traceable. For the integrity of records, there is the need for systematic management policies and procedures to guard against alteration and fraud. This again explains the need to capture a complete and auditable record of a record’s provenance as an important indicator of the record’s integrity. The risk of fraud in the provenance record (in addition to fraud in the record itself), has led to the development of secure provenance, especially in the electronic records. Also, the systems themselves need to have integrity. The perceived need for system integrity is also helping to build the case for the transparency. Another aspect of integrity is the contextual and structural integrity of the content of records. This includes the physical and logical format and the relationships between content elements. Failure to maintain the structural integrity of the records can damage a record’s reliability and authenticity. It also has an impact on the record’s usability.
Record-keeping – It is the systematic creation, use, maintenance, and disposition of records to meet administrative, programmatic, legal, and financial needs and responsibilities.
Record management – As per the ‘records management standards’ ISO 15489.1, records management is the ‘field of management responsible for the efficient and systematic control of the creation, receipt, maintenance, use and disposition of records, including processes for capturing and maintaining evidence of and information about business activities and transactions in the form of records’.
Record reliability – A reliable record is defined as one whose contents can be trusted as a full and accurate representation of the transactions, activities or facts to which they attest and can be depended upon in the course of subsequent transactions or activities. Records are required to be created at the time of the transaction or incident to which they relate, or soon afterwards, by individuals who have direct knowledge of the facts or by instruments routinely used within the organization to conduct the activity or transaction. The background of the record’s creation is important in determining its reliability. Automated, real-time capture of objective transaction information normally has the highest reliability, whereas timely first-hand accounts by individuals have slightly less reliability, as the content is necessarily filtered through personal subjective interpretation. Also, the record’s provenance or lineage can be used as evidence in support of a record’s reliability, with records created at the time of the event considered to be the most reliable.
Record usability – A usable record is one which can be found and understood in its original context. A usable record can be located, retrieved, presented, and interpreted. It is to be capable of later presentation as directly connected to the organizational activity or transaction which produced it. The contextual linkages of records are to carry the information needed for an understanding of the transactions which created and used them. It is to be possible to identify a record within the context of broader organizational activities and functions. The links between records which document a sequence of activities are to be maintained. There are hence two aspects of a record’s usability namely (i) the usability of the record itself, and (ii) the functionality of the system which is managing the record. To keep an individual record usable, it is to be preserved over time. In general, the main objective of preservation is to allow future users to retrieve, access, decipher, view, interpret, understand, and experience documents, data, and records in meaningful and valid (that is, authentic) ways. One of the challenges for preservation is that records are to be altered to preserve them, and this impact on the record’s integrity and authenticity. Hence, a balance is to be maintained between authenticity and usability. The second aspect of usability relates to the functionality of the system in which the record is being managed. The system is to have capability so that a usable record can be located, retrieved, presented and interpreted. In order to do that, sufficient information is to be captured about the record and the context of its creation and use. This information is to be sufficient to locate the record, while the contextual linkages are to provide an understanding of the transactions which created and used them.
Recoverable heat – It is the thermal energy generated as a byproduct of a process or system which is captured and reused for other beneficial purposes, rather than being wasted into the environment. This process, known as heat recovery, aims to increase overall energy efficiency, reduce energy costs, and decrease emissions by repurposing heat from sources like industrial exhaust gases, engines, or other equipment.
Recoverable reserves – These are the parts of a mineral deposit which can be technically, economically, and legally extracted at the current time and under existing conditions. Unlike total resources, recoverable reserves have been evaluated for profitability and the feasibility of extraction with current technology and regulations, and are projected to be an organization’s future assets which can be monetized and affect its value.
Recovered heat – It is thermal energy generated by a process which is captured and reused for another useful purpose instead of being lost to the environment. This heat is recovered using technologies such as heat exchangers, recuperators, and regenerators to preheat materials, generate steam, or even produce electricity, hence increasing overall energy efficiency and reducing energy costs and carbon emissions.
Recovery – It is the time-dependent portion of the decrease in strain following unloading of a sample at the same constant temperature as the initial test. Recovery is equal to the total decrease in strain minus the instantaneous recovery. It is also the reduction or removal of work-hardening effects in metals without motion of large-angle grain boundaries. Recovery is the proportion of the desired component obtained by processing an ore, normally expressed as a percentage. Recovery is also the percentage of valuable metal in the ore which is recovered by metallurgical treatment. Recovery also refers to different processes including recovering valuable products from a waste stream (e.g., product recovery from solid substrates) or materials from their original form, restoring a product or component to a functional state (e.g., remanufacturing), and returning a material to its original properties after deformation (e.g., in metallurgy). It can also refer to the recovery of energy or the process of a system returning to its normal operational state after a failure or disruption, such as in disaster recovery plans.
Recovery boiler – In the pulp and paper industry burns black liquor to recover inorganic chemicals (such as sodium sulphate) for reuse and to generate steam by combusting the organic components of the black liquor for energy. The process involves spraying concentrated black liquor into a furnace, where it is burned with air. The inorganic chemicals form a molten smelt at the bottom of the furnace, while heat is captured to produce steam in the boiler’s water-filled walls and tubes.
Recovery efficiency – It is a measurement of how successfully a desired product, substance, or energy is collected or retrieved from a system or process, compared to the amount which is originally present or can potentially be recovered. It involves a ratio of recovered material to the total available material. The process of determining this efficiency involves calculating initial and final quantities, then applying a specific formula unique to the context of the recovery.
Recovery Hopkinson bar techniques – These techniques are also known as momentum trapping techniques. They are used to study the dynamic mechanical behaviour of materials under high strain rates by trapping residual stress waves using momentum trap bars, allowing for samples recovery after testing.
Recovery mechanisms – These are processes or strategies designed to restore systems, data, or functionality to a usable state after a failure, disruption, or damage. These mechanisms aim to minimize downtime, data loss, and operational disruption.
Recovery rate – It is the ratio of the number of parts scrapped to the total number of parts manufactured, expressed as a percentage.
Recovery ratio – It can refer to different concepts depending on the field, but it normally indicates the proportion of something successfully restored or returned after a process, such as the quantity of fresh water produced from seawater in desalination, the quantity of material successfully retrieved in soil sampling, or the extent of elastic deformation which reverts after a load is removed.
Recovery stress – It is the internal stress which develops in a material when it attempts to return to its original shape after a deformation but is physically restrained by its surrounding structure or material. This phenomenon is notably relevant in the context of shape memory alloys (SMAs), where a material is first deformed, then heated while constrained, causing it to exert a momentous force (the recovery stress) as it tries to regain its pre-deformed shape.
Recrystallization – It is the formation of a new, strain-free grain structure from that existing in cold-worked metal, normally accomplished by heating. It is also the change from one crystal structure to another, as occurs on heating or cooling through a critical temperature. Recrystallization is a process, normally physical, by which one crystal species is grown at the expense of another or at the expense of others of the same substance but smaller in size.
Recrystallization annealing – It consists of annealing cold-worked metal to produce a new grain structure without phase change.
Recrystallization controlled rolling (RCR) – Although conventional controlled rolling can lead to very fine ferrite grain sizes, the low finishing temperature (750 deg C to 900 deg C) of this method leads to increased rolling loads for heavy plate and thick-walled seamless tube. For thicker sections, recrystallization-controlled rolling is used to refine austenite grain size. This process can result in ferrite grain sizes on the order of 8 micrometers to 10 micrometers. Recrystallization controlled rolling involves the recrystallization of austenite at successively lower temperatures below roughing temperatures but still above 900 deg C. Recrystallization is not to be sluggish for this method to succeed, and hence vanadium can be beneficial because vanadium carbide is readily dissolved at rolling temperature and hence unavailable for suppressing recrystallization. However, vanadium steels need stable carbonitrides, such as titanium nitride, to retard grain growth after recrystallization. Niobium steels, on the other hand, can undergo recrystallization-controlled rolling at higher temperatures with Nb(C,N) precipitates eventually forming. This precipitation of Nb(C,N) restricts austenite grain growth and can preclude the need for a titanium addition.
Recrystallization kinetics – It is the study of the time-dependent nature of recrystallization, which is the process in materials science where deformed grains are replaced by new, strain-free grains. It describes how quickly and to what extent recrystallization occurs over time and is influenced by factors like temperature, the quantity of prior deformation (stored energy), and the mobility of grain boundaries. The process can be quantified using models like the Avrami equation (or JMAK theory), tracking the volume fraction of recrystallized material as a function of time and annealing conditions.
Recrystallization temperature – It is the approximate minimum temperature at which complete recrystallization of a cold-worked metal occurs within a specified time.
Recrystallization texture – It refers to the preferred orientation (or texture) of crystals which form during the recrystallization process, which is the replacement of deformed grains with new, strain-free grains.
Recrystallized grain size – It is the grain size which is developed by heating cold-worked metal. The time and temperature are selected so that, although recrystallization is complete, essentially no grain growth occurs. In aluminum and magnesium alloys, it is the grain size after recrystallization, without regard to grain growth or the recrystallized conditions.
Rectangle – It is a two-dimensional quadrilateral (four-sided polygon) with four right angles and opposite sides which are equal in length and parallel to each other.
Rectangular channel – It is a conduit with a uniform rectangular cross-section used to direct fluid flow, frequently in open-channel hydraulics or micro-fluidic systems. It has a defined width and depth, allowing for the calculation of hydraulic properties like wetted area and wetted perimeter, which are crucial for understanding flow behaviour and designing efficient channel systems.
Rectangular coordinates – These are also known as Cartesian coordinates. They define a point’s position on a plane or in space using two or three perpendicular axes (x, y, and z) which intersect at a central point called the origin. Each point is represented by an ordered pair (x, y) or triplet (x, y, z), where the numbers indicate the distance from the origin along each respective axis. This system is fundamental for mapping locations, representing data, and defining object positions in computer graphics and engineering.
Rectangular cross section – It is a geometric shape characterized by two perpendicular sides, with dimensions denoted as b1 (longer side) and b2 (shorter side), where the angle alpha represents the orientation of the longer side relative to the flow component in the cross-sectional plane.
Rectangular hollow section (RHS) – It is a structural steel product with a rectangular outer shape and a hollow interior, frequently referred to as a box section. It offers a high strength-to-weight ratio and is highly versatile in construction and manufacturing because of its flat surfaces, which simplify joining, welding, and fabrication processes. Rectangular hollow section is durable, resistant to environmental factors, and can withstand extreme temperatures, making it suitable for a wide range of industrial applications.
Rectangular lifting magnet – It is built with either of two basic magnetic circuits, the two-pole or three-pole circuit, and it also can be permanent or electro-magnet. Pole plate and core material are normally hot rolled steel or low carbon steel. For the plates of rectangular lift magnets hot rolled steel plate is welded and joined into the required box shape. Using these stock materials, there is no limitation to lift magnet geometry.
Rectification – It consists of work done to correct dimensional errors. In chemical engineering, rectification is a thermal separation process, which is also known as counter-current distillation, that concentrates a volatile mixture by repeatedly vaporizing and condensing the mixture, resulting in a higher purity of the more volatile component. Rectification aims to improve the purity of a substance through repeated distillation cycles, unlike simple distillation which separates components based on boiling points. It involves a multi-stage distillation process carried out in a column, where vapor and liquid streams interact in a counter-current manner. Rectification is also the mechanism by which out-of-band radio frequency and microwave signals are converted to in-band signals. This process is very much an envelope detector. In electrical engineering, rectification is the process of converting alternating current to direct current, typically achieved using devices like diodes which allow current to flow in only one direction.
Rectifier – It is a device which converts alternating current (which periodically reverses) to direct current which flows in only one direction. Rectifier can be a solid-state, vacuum tube, or electro-mechanical device.
Rectifier transformers – These are specialized transformers which are used to convert alternating current to direct current in various applications, such as industrial power supplies, traction systems, and electrochemical processes. These transformers frequently include diodes or thyristors within the same tank. The process of rectification involves changing the direction of current flow in the circuit, and transformers are used to step down or step up the voltage level of the alternating current power supply. One of the challenges of rectifier transformers is the generation of harmonics in the output voltage waveform. Harmonics are the multiples of the fundamental frequency and can cause unwanted effects such as increased losses, electromagnetic interference, and distortion of the wave-form. To reduce the harmonic content in the output voltage, a technique called pulse rectification can be used.
Rectiformer – It is a combination of a transformer and a rectifier, which is used in electro-chemical processes or supply of electro-static precipitators.
Rectisol process – It is a physical absorption method which uses chilled methanol as a solvent to remove acid gases like carbon di-oxide (CO2) and hydrogen sulphide (H2S) from gas streams at very low temperatures, typically between -30 deg C and -75 deg C. It is a widely used process, particularly for purifying synthesis gas from coal, oil, or lignite gasification, and is known for achieving very high gas purities (e.g., less than 0.1 parts per million total sulphur).
Recuperative burner – Recuperative burners preheat incoming combustion air by capturing waste heat from exhaust gases. This preheated air enhances fuel efficiency and reduces energy consumption. They use a heat exchanger positioned within the exhaust flue. Exhaust gases leaving the furnace transfer their thermal energy to the heat exchanger, warming the incoming air stream. This preheated air then mixes with fuel, resulting in a more efficient combustion process. In case of a recuperative burner, the structure of the burner is the similar to the radiation heat exchanger tube which heats the inlet air up to the higher temperature (about 750 deg C) by recovering the heat from the exhaust gas to the inlet air. Hence, the exchanged heat in the burner can improve the combustion efficiency and save the fuel cost approximately 25 % to 30 %. Recuperative burners are frequently used in industries where moderate heat recovery is sufficient and initial cost savings are crucial, such as in small to medium-sized industrial furnaces.
Recuperative heating – It involves preheating combustion air by capturing waste heat from exhaust gases using a heat exchanger, improving combustion efficiency and fuel economy.
Recuperator – It consists of the equipment for transferring heat from gaseous products of combustion to incoming air or fuel. The incoming material passes through pipes surrounded by a chamber through which the outgoing gases pass. Recuperator normally recovers heat from the exhaust gases of a furnace of medium temperature or high temperature and transfer it to incoming combustion air. Recuperators can be categorized by the relative directions of gas flow such as (i) ‘in parallel-flow heat exchangers’ where both the gases flow in the same general direction, (ii) ‘in counter flow exchangers’ where both the gases flow in opposite directions, or (iii) ‘in cross-flow’ where the gases flow at right angles to each other. Counter flow heat exchangers have the greatest effectiveness while the parallel flow arrangement has the lowest effectiveness. Recuperators can be based on the principle of heat transfer by radiation, convection, or combinations. Recuperators are constructed out of either metallic or ceramic materials. Metallic recuperators are used in applications with temperatures below 1,050 deg C, while heat recovery at higher temperatures is better suited to ceramic tube recuperators which can operate with hot side temperatures as high as 1,500 deg C and cold side temperatures of around 950 deg C.
R-curve – It is a plot of crack-extension resistance as a function of stable crack extension, which is the difference between either the physical crack size or the effective crack size and the original crack size. R-curves normally depend on sample thickness and, for some materials, on temperature and strain rate. It is also known as J-R curve.
Recurrent neural network (RNN) – It is a type of artificial neural network designed to process sequential data, like text or time-series, by using a ‘memory’ to retain information from previous inputs and feed it back into the network to influence current outputs. Unlike standard feedforward networks, recurrent neural networks have feedback loops, enabling them to recognize patterns, dependencies, and context over time, making them suitable for tasks like speech recognition, language translation, and text generation.
Recursive least squares (RLS) filter – It is an adaptive filter algorithm which recursively finds the coefficients that minimize a weighted linear least squares cost function relating to the input signals. This approach is in contrast to other algorithms such as the least mean squares (LMS) which aim to reduce the mean square error.
Recyclability – It is the ability of a product or material to be collected, sorted, and processed to be transformed into new products or raw materials for new applications. It is a property of materials which can be economically recovered and reprocessed into new items, reducing waste and conserving natural resources.
Recycle gas compressor – It compresses and circulates gas within a closed-loop system, reintroducing a portion of the processed gas back to its inlet to maintain process conditions, control pressure, and improve efficiency by maximizing resource utilization in processes like hydrotreating and catalytic reforming. This ‘hot gas recycling’ is a common technique where compressed gas is sent back to an earlier point in the system, rather than exiting as a waste stream, to either ensure stable operation or to increase the overall flow rate of reactants.
Recycling – It is the process by which salvaged materials become usable products. It is the process of converting waste products into reusable materials. Recycling differs from reuse, which simply means using a product again.
Recycling process – It involves collecting waste materials like plastics, paper, glass, and metals, followed by sorting them into categories, cleaning, and processing them into their raw forms. These raw materials are then used to manufacture new products, which reduces the need for virgin raw materials, conserves energy, and minimizes pollution and landfill waste.
Red brass – It is a type of brass alloy, characterized by a reddish tint because of a high copper content (typically 77 % to 86 %). It finds applications in plumbing, industrial components, electrical hardware, and decorative items because of its durability, corrosion resistance, and machinability. Red brass fittings and components are widely used for pump housings, impellers, and valves because of their ability to resist saltwater corrosion. These components ensure reliable performance for vessels and offshore equipment.
Redesign – It is the process of redoing an existing design to improve some deficiency in the existing design.
Red mud – It is a residue, containing a high percentage of iron oxide, obtained in purifying bauxite in the production of alumina in the Bayer process. In fretting wear, a mud is powdery form of debris, normally consisting of iron oxides, which is expelled from a ferrous metal joint near the location where fretting wear is occurring.
REDOP process – It has developed to recycle mixed plastic waste into blast furnaces. A mixed plastics/paper fraction is recovered from municipal waste and further separated into a plastic fraction and a paper fraction. The former is de-halogenated by a new process patented by DSM Research. In this de-halogenating process, a slurry of waste in water is heated in a stirred reactor. The released hydro-chloric acid is neutralized by addition of a diluted water-soluble base. The non-halogenated plastics melt into droplets, the size of which is determined by the stirring and by the traces of cellulose still present. Upon cooling, the plastic droplets solidify, yielding mixed plastic (MP) granules having size and characteristics well suited to pneumatic injection in the blast furnace. The chlorine content is comparable to coal and the calorific value is at least equivalent.
Redox – It is also called reduction–oxidation or oxidation–reduction. It is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state. The oxidation and reduction processes occur simultaneously in the chemical reaction. There are two classes of redox reactions. The first is electron-transfer in which only one (normally) electron flows from the atom, ion, or molecule being oxidized to the atom, ion, or molecule which is reduced. This type of redox reaction is frequently discussed in terms of redox couples and electrode potentials. The second is atom transfer in which an atom transfers from one substrate to another, e.g., in the rusting of iron, the oxidation state of iron atoms increases as the iron converts to an oxide, and simultaneously, the oxidation state of oxygen decreases as it accepts electrons released by the iron. Although oxidation reactions are normally associated with forming oxides, other chemical species can serve the same function. In hydrogenation, bonds like C=C are reduced by transfer of hydrogen atoms.
Redox equilibrium – It refers to a state where the rates of oxidation and reduction reactions are equal, meaning that there is no net change in the concentrations of reactants and products in a redox system. Redox equilibrium play an important role in the electron transport chain.
Redox potential – it is the potential of a reversible oxidation-reduction electrode measured with respect to a reference electrode, corrected to the hydrogen electrode, in a given electrode.
Red phosphorus – It is a polymeric and thermally stable allotropic form of phosphorus, effective as a flame-retardant additive in polymers, particularly at concentrations below 10 %. It is relatively nontoxic and acts by quenching free radicals and reducing heat production during combustion, although it can react with moisture to produce toxic phosphine gas.
Redrawing – It is the second and successive deep-drawing operations in which cup-like shells are deepened and reduced in cross-sectional dimensions.
Redraw rod – The preferred term is drawing stock.
Red shift – It is a systematic displacement toward the longer wavelengths of the spectrum.
Redsmelt process – It is an ironmaking process which is based two reduction steps. These are (i) pre-reduction of iron bearing materials in a rotary hearth furnace (RHF), and (ii) smelting of the hot pre-reduced iron (DRI, direct reduced iron). Originally a submerged arc furnace (SAF) has been used for the second step. Submerged arc furnace has now been replaced by a coal and oxygen blown converter (oxy-coal reactor) known as ‘New Smelting Technology’ (NST). The rotary hearth furnace reduces green pellets made out of iron ore, reductant fines and binders to produce hot, metallized direct reduced iron which is charged to the NST converter for its smelting to hot metal.
Reduce or reduction – It refers to a chemical process where a substance gains electrons, or experiences a decrease in its oxidation state.
Reduce, reuse, and recycle – These are frequently referred to as the three ‘Rs’ These are fundamental principles in sustainable waste management and environmental conservation. These principles are essential in minimizing waste generation, maximizing resource efficiency, and reducing the negative impact on the environment. Reduce emphasizes the importance of reducing the quantity of waste being produced. This principle involves being mindful of the consumption habits and making conscious choices to minimize waste generation. Reuse encourages to find ways to extend the lifespan of items instead of discarding them after a single use. Reusing items is a powerful way to minimize waste and conserve resources. By embracing the concept of reuse, it is possible to reduce the demand for new products and decrease the quantity of waste generated. Recycle is the process of converting waste materials into new products to prevent the waste of potentially useful materials. This practice helps conserve natural resources, reduce energy consumption, and decrease greenhouse gas emissions. By separating recyclable materials from general waste and supporting recycling programs, it is possible to contribute to a more sustainable and circular economy.
Reduced metal powder – It refers to metal powder produced by chemically reducing metal oxides or compounds with a reducing agent, like carbon or hydrogen, without melting the metal.
Reduced-ply belt – Reduced-ply belts consist of carcasses with either fewer plies than comparable multiple-ply belts or special weaves. The features of reduced-ply belt include (i) straight warp ply carcass structure which allows designs to provide higher tension than ordinary multi-ply belts, (ii) provides high bendability and impact resistance, and (iii) belts can be easily joined.
Reducer – It is a pipe fitting which is used to join two different pipe sizes together. Reducers can be either concentric or eccentric which refers to the relative position of the center lines of the outlet and inlet. Special attention is to be given when using reducers in a horizontal orientation as the slope prevents free draining of a system if not installed correctly.
Reducer rolling – It is also known as roll forging. It is a longitudinal rolling process which reduces the cross-sectional area of heated bars or billets by passing them between two rotating roll segments with forming grooves, creating workpieces with varying cross-sections along the rolling direction.
Reducers – The reducers change the number of revolutions of the electric motor to the required revolutions of the rolls. They increase the torque. They can be one-stage, two-stage and three-stage type. The gear ratio of each stage can range from 4 to 6.
Reducibility – Reducibility refers to the ease with which a substance can be reduced, meaning the tendency to gain electrons or have its oxidation state decreased during a chemical reaction. It also means being capable of being reduced or made simpler, smaller, or less in size, amount, degree, or importance. In a more technical context, it refers to the ability to solve a problem by transforming it into a simpler, known problem.
Reducibility index (RI) – Reducibility index of iron ore sinter is a metallurgical property which measures how easily the iron oxides in the ore can be removed to form metallic iron by a reducing gas, a crucial factor for blas furnace operations. A higher reducibility index indicates that the sinter is of better quality since it can be reduced more readily, leading to a smoother and more efficient smelting process and better permeability of the burden in the blast furnace.
Reducing agent – It is also known as a reductant, reducer, or electron donor. It is a compound which causes reduction, thereby itself becoming oxidized. It is also a chemical which, at high temperatures, lowers the state of oxidation of other batch chemicals. Reducing agent is a chemical species which donates an electron to an electron recipient (called the oxidizing agent, oxidant, oxidizer, or electron acceptor). Examples of substances that are common reducing agents include hydrogen, carbon mono-oxide, the alkali metals, formic acid, oxalic acid, and sulphite compounds. Reducing agents in the blast furnace are carbon of coke, and the carbon mono-oxide gas generated in the furnace by the combustion of coke and injected pulverized coal.
Reducing atmosphere – It is a furnace atmosphere which tends to remove oxygen from substances or materials placed in the furnace. It is an atmosphere which tends to (i) promote the removal of oxygen from a chemical compound, and (ii) promote the reduction of immersed materials. It is also a chemically active protective atmosphere which at high temperature reduces metal oxides to their metallic state. Reducing atmosphere is a relative term and such an atmosphere can be reducing to one oxide but not to another oxide.
Reducing flame – It is a gas flame which is produced with excess fuel in the inner flame. It is also a gas flame resulting from combustion of a mixture containing too much fuel or too little air.
Reducing and sizing block (RSB) mill – It is a sophisticated finishing mill stand in a rod and bar mill, typically using 3-roll technology, which combines heavy-duty reducing passes for substantial diameter reduction and high-precision sizing passes to achieve tight tolerances and a smooth surface finish on steel bars. Its key advantage is the high flexibility and productivity it offers by allowing for a wide range of finished sizes to be rolled with minimal roll set changes, utilizing rapid remote-control adjustments of rolls and guides.
Reducing and sizing mill (RSM) – It is a type of rolling mill which is used to reduce the diameter (and potentially the wall thickness) of pipes or bars, improving their accuracy and surface quality. This mill is frequently located between the finishing block mill and the high-speed laying head. It is normally designed with a split structure and independent twin-module block transmissions, it ensures flexibility and ease of production and maintenance. It uses a series of rollers or stands to progressively reduce the diameter of the product, frequently while also adjusting the wall thickness to achieve the desired dimensions.
Reducing tee – It is a pipe fitting, in a T-shape, where the branch outlet has a smaller diameter than the two main ‘run’ ports, allowing for a change in fluid flow diameter in a piping system. It combines the functions of a tee and a reducer into a single fitting, enabling a smaller pipe to branch off from a larger main line.
Reducing valve – It is a regulating device which serves to reduce the fluid pressure supply to the needed delivery pressure. Reducing valve automatically reduces supply pressure to a pre-selected pressure as long as the supply pressure is at least as high as the selected pressure. The main parts of the reducing valve are the main valve, an upward-seating valve which has a piston on top of its valve stem, an upward-seating auxiliary (or controlling) valve, a controlling diaphragm, and an adjusting spring and screw.
Reductant – It is also called reducing agent. It is a substance, such as carbon or hydrogen, which causes the reduction of a metal oxide by donating electrons and removing oxygen, thereby producing a pure metal. The reductant itself is oxidized in the process, which is a fundamental step in many processes of extractive metallurgy, like the blast furnace for iron production.
Reduction – In cupping and deep drawing, it is a measure of the percentage decrease from blank diameter to cup diameter, or of diameter reduction in redrawing. In forging, rolling, and drawing, it is either the ratio of the original to final cross-sectional area or the percentage decrease in cross-sectional area. Reduction is also a reaction in which there is a decrease in valence resulting from a gain in electrons. It is the removal of oxygen from a chemical compound. In sampling, reduction is the process of preparing one or more sub-samples from a sample. Reduction can also refer to decreasing the valence of an ion or atom by the addition of electrons.
Reduction cell – It is a pot or tank in which either a water solution of a salt or a fused salt is reduced electrolytically to form free metals or other substances.
Reduction disintegration index (RDI) – In the upper part of the blast furnace shaft, the permeability of the burden can be influenced by the breakdown of sinter upon reduction. The reduction disintegration index is defined as a quantitative measure of the disintegration of the sinter which can occur in the upper part of the blast furnace after some reduction. Sinter with a high degree of reduction disintegration generates fines in the top of the furnace which affects the flow distribution within the blast furnace.
Reduction gear boxes / reducers – The reduction gear boxes / reducers are used in the rolling mills where speed of motor is higher than required for rolls. Depending on the required reduction in speed, reducers can be used having 1, 2 or 3 stages.
Reduction in area (RA) – It is the difference between the original cross-sectional area of a tensile sample and the smallest area at or after fracture as specified for the material undergoing testing. It is also known as reduction of area.
Reduction mechanism – It is the detailed step-by-step process by which a chemical species gains electrons, resulting in a decrease in its oxidation state and often a gain in hydrogen or a loss of oxygen. Examples include the gain of electrons in redox reactions.
Reduction of oxide – It refers to the process of removing oxygen from metal oxide particles (like iron oxide) in the powder, typically during the sintering stage, to produce a pure metal powder or a metal with desired properties. It is the process of converting a metal oxide to metal by applying sufficient heat in the presence of a solid or gaseous material, such as hydrogen, having a higher attraction for oxygen than does the metal.
Reduction- oxidation (Redox) processes– These processes are used for the chemical oxidation or chemical reduction. These involve use of oxidants or reductants to bring about a change in the chemical composition of a compound or group of compounds to less harmful or hazardous compounds.
Reduction potential – It EredEhis a measure of the tendency of a chemical species to acquire electrons from or lose electrons to an electrode and hence be reduced or oxidized respectively. Redox potential is expressed in volts (V). Each species has its own intrinsic redox potential, e.g., the more positive the reduction potential (reduction potential is more frequently used because of the general formalism in electro-chemistry), the higher the species’ affinity for electrons and tendency to be reduced.
Reduction ratio – It refers to the ratio of the volume of the loose powder to the volume of the final compact or part produced after compaction. It is also the quotient of the reduced oxygen content into the total initial content of a powder. In mechanical working, it is the quotient of the reduced cross-section into the original cross-section in metal working such as extrusion, it is an indication of the degree of plastic deformation.
Reduction reaction – In electro-chemistry, it is a chemical reaction which is taking place at cathodic sites by the consumption of electrons.
Reduction roasting – Reduction roasting is the removal of oxygen from a component of an ore normally by using a reductant such as carbon mono-oxide. The rotary kiln is used as a reduction furnace. It can employ a wide range of carbon carriers not suitable as reductants for shaft furnaces from anthracite and coke breeze to charcoal fines, lignite, and brown coal. The charge (ore and reductant) normally moves through the rotary kiln counter-current to the hot gases. Coupled reactions mainly ore reduction by carbon mono-oxide gas and reaction of carbon with carbon di-oxide with regeneration of carbon mono-oxide, occur in the charge. The reactivity of carbon is critical for the process as a whole. Some of the carbon mono-oxide gas formed escapes from the charge so that oxidizing gases from the free kiln volume cannot permeate into it. Reducing conditions depend on (i) the temperature, reactivity, and quantity of the reductant, (ii) the residence time, and (iii) the charge holdup at the discharge end of the kiln. The rate of reduction can be controlled to meet a variety of objectives, from the formation of magnetite (Fe3O4) to the production of direct reduced iron (DRI).
Redundancy – It is the intentional duplication of critical components or functions of a system with the goal of increasing reliability of the system, normally in the form of a backup or fail-safe, or to improve actual system performance.
Redundancy parameter – It is a value which defines the quantity of overlap or unnecessary information in a system, model, or data set, indicating that some elements can be expressed in terms of others, leading to non-identifiability or inefficiencies. In engineering and statistics, it can quantify shared predictive information or the ability of a model to be reparametrized with fewer variables. In a database context, a redundancy parameter defines the minimum number of backups of each data file to retain, ensuring data availability.
Redundant – It applies to things which are unnecessary or can be left out.
Redundant switches – These refer to critical devices equipped with dual network paths, allowing them to maintain operation by connecting to two Ethernet interfaces linked to separate switches in the event of a network failure.
Redwood viscosity – It is a commercial measure of viscosity expressed as the time in seconds needed for 50 cubic centimeters of a fluid to flow through a tube of 10 millimeters length and 1.5 millimeters diameter at a given temperature.
Reed switch – It is a magnetically activated electro-mechanical switch, consisting of two ferro-magnetic reeds (flexible metal contacts) sealed inside a hermetic glass envelope. When exposed to a magnetic field from a permanent magnet or electro-magnetic coil, the reeds are pulled together, closing the electrical circuit. When the magnetic field is removed, the reeds return to their original position, opening the circuit.
Reel – It is a spool or hub for coiling or feeding wire or strip. It also means to straighten and planish a round bar by passing it between contoured rolls.
Reel breaks – These are transverse breaks or ridges on successive inner laps of a coil which results from crimping of the lead end of the coil into a gripping segmented mandrel. These are also called reel kinks.
Reentrant angle – It is an interior angle of a polygon higher than 180-degree.
Reference – It is a physical feature which is used to establish position and measurement.
Reference accident – It is one of a range of accidents at a nuclear reactor or other nuclear installation that can reasonably be foreseen in safety analysis as giving rise to the most significant release of radionuclides from the site. It refers to a hypothetical or specific accident scenario which is used as a benchmark or standard for safety analysis, emergency planning, or design criteria.
Reference data – It is a set of static, non-transactional values or codes which provides context and meaning to other data within an organization or across systems, enabling consistent interpretation, classification, and accurate analysis. It acts as a standard, frequently mandated by regulators, to classify entities (like customers or products), define relationships, and establish common definitions for reporting and integration across different systems.
Reference designation – It is a unique code, typically a letter or two followed by a number (e.g., C3, R15), which identifies a specific component or element on a bill of materials, within an electrical schematic or printed circuit board (PCB). This standardized system allows engineers, technicians, and assemblers to accurately locate and reference parts during design, manufacturing, and troubleshooting, ensuring clarity and consistency in documentation and complex systems.
Reference designator – It is a unique, standardized alphanumeric code (like R1, C5, U10) which identifies a specific component on a printed circuit board (PCB), in an electrical schematic, or on a bill of materials (BOM). This system ensures clear communication and accurate tracking of components during the entire product lifecycle, from design and manufacturing to assembly, troubleshooting, and maintenance.
Reference document – It is a supplementary text or document which provides context, information, or a standard for another document or activity, but is not a core part of the main agreement itself. These documents can include specifications, guidelines, prior contracts, policies, or other supporting materials which are referenced within a main document to make it more comprehensive and ensure clarity.
Reference electrode – It is a non-polarizable electrode with a known and highly reproducible potential used for potentiometric and voltametric analyses.
Reference line – In data visualization and other contexts, it is a line which is used to provide a visual reference point for comparison or context within a chart, graph, or other visual representation. It can be a horizontal or vertical line indicating a threshold, a target value, or a specific data point. Reference lines help users interpret data by providing a visual anchor against which to compare the data points displayed in a chart or graph.
Reference material – In materials characterization, it is a material of definite composition which closely resembles in chemical and physical nature of the material with which an analyst expects to deal. It is a material or substance, one or more of whose property values are sufficiently homogeneous and well established to be used for the calibration of an apparatus, the assessment of a measurement method, or for assigning values to materials. It is a reference material which can be in the form of a pure or mixed gas, liquid or solid. Examples are water for the calibration of viscometers, sapphire as a heat-capacity calibrant in calorimetry, and solutions used for calibration in chemical analysis. Reference material is used for calibration or standardization.
Reference plane – It is a foundational flat surface used as a standard for measurement, alignment, or defining a coordinate system in different fields. It provides a reliable point of comparison for other objects or planes, ensuring accuracy and consistency in design and measurement processes.
Reference point – It is a fixed position near the top of a tank used for accurate level gauging, which can be a plate, a groove, or a fixed arm that does not contact the gauging hatch.
Reference sample – It is a carefully selected sample or material which is used as a benchmark for comparison with other samples, hence, ensuring quality consistency and serving as a standard for analysis and evaluation.
Reference temperature – It is the temperature of collapse of pyrometric cone. It is the temperature at which the tip of a pyrometric reference cone reaches the level on which the base of the cone is mounted when the cone is heated at a specified rate under specified conditions.
Reference view – It refers to one of the standard orthographic projections (such as the front, top, or side view) which serves as a primary representation of the object from a particular perspective. These views are projected onto reference planes or principal planes of projection, which are imaginary planes used to establish the orientation and position of the object in space.
Refined aluminum – It is the aluminum of very high purity (99.95 % or higher) achieved by special metallurgical treatments.
Refined copper – It is the metal containing at least 99.85 % of copper, or metal containing at least 97.5 % of copper, provided that the content of any other element does not exceed the limit specified as silver -0.25 %, arsenic 0.5 %, cadmium 1.3 %, chromium 1.4 %, magnesium 0.8 %, lead 1.5 %, sulphur 0.7 %, tin 0.8 %, tellurium 0.8 %, zinc 1 %, zirconium 0.3 % and other elements, each 0.3 %. Other elements are, e.g., aluminum, beryllium, cobalt, iron, manganese, nickel, and silicon. Refined copper is produced by electrolytic refining, electrolytic extraction, chemical refining or fire refining. Other refined copper (containing at least 97.5 % by weight of copper) is normally produced by alloying refined copper with one or more other elements up to the maximum content limits as given above. In practical application, it applies to refinery shapes which are directly consumed without further refining.
Refined natural gas – It is the purified and processed form of raw natural gas, mainly composed of methane, which has been stripped of impurities such as water, carbon di-oxide, and hydrogen sulphide to meet pipeline or sales gas quality specifications. This conditioning process, which also removes heavier hydro-carbons and other non-combustible substances, makes the gas suitable for transportation and use in applications like electricity generation and heating, or for the further recovery of valuable by-products like ethane, propane, and butane.
Refined steel – It refers to steel which has undergone a process to remove impurities and unwanted elements, resulting in a purer and more desirable composition for specific applications.
Refinery – It is known as oil refinery or petroleum refinery. It is an industrial process plant where petroleum (crude oil) is transformed and refined into products such as gasoline (petrol), diesel fuel, fuel oils, asphalt base, heating oil, kerosene, liquefied petroleum gas and petroleum naphtha.
Refining – It is the branch of process metallurgy dealing with the purification of crude or impure metals. It consists of purifying an impure metal. It is to be distinguished from other processes such as smelting and calcining in that those two involve a chemical change to the raw material, whereas in refining the final material is chemically identical to the raw material. Refining hence increases the purity of the raw material through processing. There are several processes including pyro-metallurgical and hydro-metallurgical techniques.
Refining combined burner (RCB) – In the electric arc furnace, it is a system which allows for both oxygen and fuel (like coal or natural gas) to be injected into the furnace to refine the molten steel, optimizing the process and reducing maintenance costs. It is a single, automated unit which can inject both oxygen and fuel into an electric arc furnace, facilitating the refining process. It is installed on the side of the furnace, near the molten metal, and can be used to blow oxygen and fuel into the arc furnace.
Refining, copper – It consists of further purification of blister copper by removal of its oxygen content and recovery of any rare or precious metals which has been present in the ore by either (i) fire refining in a furnace, (ii) electrolytic refining, in which the blister copper is cast into anodes, suspended in an acid solution and deposited on to plates at the cathode by electrolysis.
Refining furnaces – These are industrial equipment used to heat and refine metals or other materials, mainly to increase purity or achieve a desired composition, and they are crucial in industries like steelmaking, copper refining, and metal casting.
Reflectance – Reflectance of the surface of a material is its effectiveness in reflecting radiant energy. It is the fraction of incident electromagnetic power which is reflected at the boundary. Reflectance is a component of the response of the electronic structure of the material to the electromagnetic field of light, and is in general a function of the frequency, or wavelength, of the light, its polarization, and the angle of incidence. The dependence of reflectance on the wavelength is called a reflectance spectrum or spectral reflectance curve.
Reflected beam – It is a ray or wave of energy, such as light, sound, or heat, which rebounds or bounces back from a surface it strikes. It is the ‘reflected ray’ in the process of reflection, where an incident beam (the incoming beam) hits a surface and then travels away from that surface after redirection.
Reflection – It is the change in direction of a wave-front at an interface between two different media so that the wave-front returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection (for example at a mirror) the angle at which the wave is incident on the surface equals the angle at which it is reflected. In acoustics, reflection causes echoes and is used in sonar. In geology, it is important in the study of seismic waves. Reflection is observed with surface waves in bodies of water. Reflection is observed with several types of electro-magnetic wave, besides visible light. Reflection of very high frequency (VHF) and higher frequencies is important for radio transmission and for radar. Even hard X-rays and gamma rays can be reflected at shallow angles with special ‘grazing’ mirrors.
Reflection Fresnel coefficient – It refers to the quantitative measures which describe the energy relationship between incident and reflected electro-magnetic waves at the interface of two media, determined by factors such as dielectric constant, polarization mode, and angle of incidence.
Reflection grating – It is a grating which uses reflection off a series of fine, equidistant ridges, rather than transmission through a pattern of slots, to diffract light into its component wavelengths. The gratings used in optical instrumentation are almost exclusively reflection gratings.
Reflection high-energy electron diffraction (RHEED) – Itis a surface-sensitive technique which is used to characterize the surface structure and morphology of crystalline materials, particularly during thin film growth, by analyzing the diffraction patterns of high-energy electrons grazing the sample surface. Reflection high-energy electron diffraction systems gather information only from the surface layer of the sample, which distinguishes reflection high-energy electron diffraction from other materials characterization methods that also rely on diffraction of high-energy electrons. Transmission electron microscopy, another common electron diffraction method samples mainly the bulk of the sample due to the geometry of the system, although in special cases it can provide surface information.
Reflection method – It is the technique of producing a diffraction pattern by X-rays or electrons which have been reflected from a sample surface.
Reflection polariscope – It is an optical instrument which uses polarized light to visualize internal stresses or strains in transparent materials like glass or plastics by reflecting light off the sample’s surface.
Reflection spectrum – It is a graph which shows the quantity of light, or electro-magnetic radiation, a material reflects at different wavelengths (or colours). This graph provides a unique signature for a material, revealing its composition and properties based on which wavelengths it reflects more or less. The shape of the spectrum is determined by the material’s refractive index and absorption index, with peaks and dips indicating specific reflective or absorbing properties.
Reflection, X-rays –It is the coherent scattering of X-rays by the atoms of a crystal which necessarily results in beams in characteristic directions.
Reflective factor – It is the ratio of light or radiant energy reflected by a surface to the total incident light or radiant energy it receives. It basically measures how much light a surface bounces back, expressed as a fraction or percentage. For example, a surface with a high reflective factor reflects most of the light, while a surface with a low factor absorbs most of it.
Reflective material – It is a substance with optical properties that bounce back light, rather than absorbing or transmitting it, hence increasing visibility and improving safety in low-light conditions. These materials, such as mirrors, aluminum foil, and some safety fabrics, work by reflecting light from an external source back to an observer, making objects stand out.
Reflector sheet – It is a clad product consisting of a facing layer of high-purity aluminum capable of taking a high polish, for reflecting heat or light, and a base of commercially pure aluminum or an aluminum-manganese alloy, for strength and formability.
Reflectoscope – It is a general term referring to an instrument that uses mirrors to gather, focus, and reflect light to form an image, with the most common example being the reflecting telescope. There is also a specific device called a ‘supersonic reflectoscope’ used in engineering to inspect the interior of solid parts by sending and receiving sound waves.
Reflowing – It is the melting of an electrodeposit followed by solidification. The surface has the appearance and physical characteristics of a hot dipped surface (especially tin or tin alloy plates). It is also called flow brightening.
Reflow soldering – It is a non-standard term for a soldering process variation in which preplaced solder is melted to produce a soldered joint or coated surface.
Reflux – It is the heating of a substance at the boiling temperature and returning the condensed vapours to the vessel to be reheated.
Reflux condenser – It is a device which condenses vapours, typically in a chemical reaction or distillation, and returns them to the original vessel. This process, known as refluxing, allows for continuous heating of a substance without loss of volatile components, maintaining controlled temperature and reaction conditions. It is a common and essential apparatus in several industrial chemical processes.
Reformate – It is the high-octane liquid product resulting from the catalytic reforming process, which chemically restructures low-octane naphtha from crude oil into higher-octane aromatic and isoparaffinic hydrocarbons. These aromatics, including benzene, toluene, and xylene (BTX), serve as premium gasoline blending stocks and as important raw materials for the petrochemical industry, used in the production of plastics and other chemicals.
Reformer tube – It is a high-alloy, heat-resistant pressure vessel used in industrial furnaces to produce syngas (hydrogen and carbon mono-oxide) or hydrogen through the steam reforming process. These tubes contain a catalyst to promote the endothermic reaction of hydrocarbon feedstocks at high temperatures and pressures, needing specialized materials and construction to withstand severe conditions and ensure long-term, reliable operation.
Refracted ray – It is the path of a ray of light or other electro-magnetic radiation as it changes direction when passing from one medium to another with a different optical density, such as from air into water or glass. This change in direction is caused by a change in the light’s speed, bending either towards or away from the normal line (a line perpendicular to the surface) depending on the optical properties of the two media, a phenomenon governed by Snell’s law.
Refracting surface – It is a boundary between two transparent media where light bends, or refracts, causing a change in its direction and speed. These surfaces, which can be flat or curved (like spherical surfaces), are fundamental components in optical systems, such as lenses and telescopes, and are designed based on principles like Snell’s law to control and focus light.
Refractive index – Refractive index of a medium is a dimensionless quantity representing the ratio of the speed of light in a vacuum to the speed of light in that medium. It quantifies how much light slows down and bends when passing from a vacuum (or air) into that specific medium, with a higher refractive index indicating a slower speed of light and a greater bending of the light rays. Refractive index is a standard of measurement used particularly to establish the qualities of optical glass. The index is the ratio of the sine of the angle of incidence of a ray of light to the sine of the angle of refraction (the change in direction when a ray of light passes from one medium to another) by the glass. The second medium normally used to establish the index is a vacuum.
Refractive power – It is the measure of an optical element’s ability to converge or diverge light, measured in diopters (D). It is calculated as the reciprocal of the focal length (in meters) and represents how strongly a lens or mirror bends light. A higher refractive power indicates a shorter focal length and a higher ability to change the path of light rays.
Refractory – It is a material of very high melting point with properties which make it suitable for such uses as furnace linings and kiln construction. It is also the quality of resisting heat.
Refractories – These are inorganic, non-metallic, porous, and heterogeneous materials which are composed of thermally stable mineral aggregates, a binder phase, and additives. The principal raw materials used in the production of refractories are the oxides of silicon, aluminum, magnesium, calcium, and zirconium. There are some non-oxide refractories like carbides, nitrides, borides, silicates and graphite. Refractories are heat resistant materials used in almost all processes involving high temperatures and / or corrosive environment. Refractories insulate and protect furnaces and vessels due to their excellent resistance to heat, chemical attack, and mechanical damage. Refractories are defined as non-metallic materials having those chemical and physical properties that make them applicable for structures or as components of systems that are exposed to environments above 540 deg C.
Refractories, acid – These are refractories which contain a substantial quantity of silica which can react chemically with basic refractories, basic slags, or basic fluxes at high temperatures.
Refractories, basic – These are refractories whose major constituent is lime, magnesia, or both, and which can react chemically with acid refractories, acid slags, or acid fluxes at high temperatures. Commercial use of this term also includes refractories made of chrome ore or combinations of chrome ore and dead-burned magnesite.
Refractories, neutral – These are refractories which are resistant to chemical attack by both acid and basic slags, refractories, or fluxes at high temperatures.
Refractoriness – It is the characteristic property of a refractory which allows it to withstand a high temperature in its environment and conditions of use. It is the capability of maintaining a desired degree of chemical and physical identity at high temperatures and in the environment and conditions of use.
Refractoriness-under-load (RUL) – It is a particular measure of the behaviour of a refractory subjected to the combined effects of load, rising temperature and time. It evaluates the softening behaviour of fired refractory bricks at rising temperature and constant load conditions. It gives an indication of the temperature at which the brick is going to collapse in service condition with similar load. However, under actual service conditions the bricks are heated only on one face and most of the load is carried by the relatively cooler rigid portion of the refractory bricks. Hence, the refractoriness under load test gives only an index of refractory quality, rather than a figure which can be used in a refractory design. Under service conditions, where the refractory used is heating from all sides such as checkers, partition walls etc. the refractoriness under load test data is quite significant. For refractoriness under load, samples in cylindrical shape of 50 millimeters height and 50 millimeters diameter are heated at a constant rate under a load of 0.2 mega pascal (MPa) and the change in height includes the thermal expansion and also the expansion of test equipment. The test results are taken from the recording. The initial temperature is taken at 0.6 % compression while the final temperature is taken at 20 % compression or when the sample has collapsed.
Refractoriness under load (differential) – In order to eliminate errors as a result of the inherent expansion of the test equipment when the refractoriness under load is being tested, and to enable tests to be carried out in an oxidizing atmosphere, a different method has been developed to determine the resistance at rising temperature and constant load which is the refractoriness under load (differential) test. In this method same type of samples are used as for the refractoriness under load test bur they have an internal bore to permit rods to be fitted to the upper and the lower sides. With this method, temperature values are obtained by differential measurements in an oxidizing atmosphere and these values are considerably lower than the refractoriness under load values.
Refractory – It is a material (normally an inorganic, non-metallic, ceramic material) of very high melting point with properties which make it suitable for such uses as furnace linings and kiln construction. It is the quality of resisting heat. It consists of non-metallic materials which are having those chemical and physical properties that make them applicable for structures, or as components of systems, which are exposed to environments above 540 deg C. Refractory also means resistant to high temperature.
Refractory alloy – It is a heat-resistant alloy. It is an alloy having an extremely high melting point. It is an alloy which is difficult to work at high elevated temperatures.
Refractory block – It is a normally rectangular refractory shape of a size larger than normally can be laid with one hand. All sides may not be plane and parallel.
Refractory brick – It is also known as a fire brick. It is a ceramic material designed to withstand high temperatures and extreme conditions. It is a normally rectangular refractory shape with one dimension higher than the other two and of a size that usually can be laid with one hand. All sides may not be plane and parallel such as wedges, arches, keys, and circle brick. They are normally used in lining furnaces, kilns, fire-boxes, and other applications requiring high-temperature resistance.
Refractory castable – It is a castable. It consists of non-coherent mixture of aggregate and bond. It is mainly supplied dry and placed by casting after the addition and mixing of water or another liquid.
Refractory cermets – These are composite materials which combine a ceramic phase (high melting point, refractory) with a metallic phase (for ductility and conductivity). These materials are designed to have high-temperature resistance, hardness, and wear resistance.
Refractory clay – It is a type of fire clay with a high melting point. It maintains its structural integrity and rigidity at extremely high temperatures, frequently exceeding 540 deg C. It is mainly composed of hydrated aluminum silicate, such as kaolin, and is used to line industrial furnaces, kilns, and other high-temperature vessels. Refractory clay fuses at PCE (pyrometric cone equivalent) 25 (1,590 deg C) or higher.
Refractory fibres – These are non-metallic, inorganic, continuous, or non-continuous filaments having those chemical and physical properties which make them applicable for structures, or as components of systems, which are exposed to environments above 540 deg C.
Refractory lining – It refers to a protective layer behind the working lining in contact with furnace contents, encased in a metal shell. It needs knowledge of mechanical properties like thermal expansion, thermal conductivity, and Young’s modulus for proper design and installation. It is the brickwork or castable used in boilers and furnaces to protect metal surfaces and for boiler baffles.
Refractory metal – It is a metal which is having an extremely high melting point and low vapour pressure, e.g., niobium, tantalum, molybdenum, tungsten, and rhenium.
Refractory ore – It is the ore which resists the action of chemical reagents in the normal treatment processes and which can need pressure leaching or other means to affect the full recovery of the valuable minerals.
Refractory organics – These organics tend to resist conventional methods of waste-water treatment. Typical examples include surfactants, phenols, and agricultural pesticides. Some of these can be toxic to the biological treatment processes.
Refractory oxide – It is a ceramic material primarily composed of metallic oxides, e.g., alumina (Al2O3), silica (SiO2), or zirconia (ZrO2), which can withstand very high temperatures (typically above 540 deg C), chemical attack, and thermal stress. These materials are important for constructing furnace linings and other components in high-temperature processes like glass and metal manufacturing, where they are to remain stable without melting, cracking, or decomposing.
Refractory relining – It refers to the process of replacing or renewing the protective layer (the lining) made of refractory materials inside a high-temperature furnace or other processing unit which has been damaged or worn down, hence ensuring structural integrity and operational effectiveness.
Refractory shape – It consists of a refractory piece which is forming a stable mass with specific dimensions.
Refractory waste – It refers to the leftover, non-recyclable material derived from the manufacturing of refractory products like bricks, castables, and ceramics. These are typically high-temperature resistant materials used in industries such as steel, glass, and cement production.
Refrigerants – These are the working fluids of refrigeration cycles which absorb heat from a reservoir at low temperatures and reject heat at higher temperatures.
Refrigeration – It consists of cooling a space, substance, or system to lower and / or maintain its temperature below the ambient one (while the removed heat is ejected to a place of higher temperature). Refrigeration is an artificial, or human-made, cooling method. It refers to the process by which energy, in the form of heat, is removed from a low-temperature medium and transferred to a high-temperature medium. This work of energy transfer is traditionally driven by mechanical means, but it can also be driven by heat, magnetism, electricity, laser, or other means.
Regeneration, catalyst – It is the process of restoring the activity or performance of a catalyst which has been deactivated due to factors such as poisoning, sintering, or ageing. It is the process of restoring the activity and performance of a deactivated catalyst by removing accumulated deposits or other deactivating agents, frequently through methods like thermal treatment or chemical washing, to extend its lifespan and maintain efficiency.
Refrigeration cycle – It is a thermodynamic process which uses mechanical work to transfer heat from a low-temperature space to a high-temperature sink, typically involving a closed loop with a refrigerant. This continuous cycle, most commonly the vapour compression cycle, consists of four main stages namely evaporation, compression, condensation, and expansion, performed by four key components namely the evaporator, compressor, condenser, and expansion valve.
Refrigeration process – It is the controlled method of extracting heat from a low-temperature region and transferring it to a high-temperature region, hence cooling the desired space or substance. This is achieved by manipulating the state of a working fluid called a refrigerant through stages of compression, condensation, expansion, and evaporation, a cyclical process which needs the expenditure of mechanical or other forms of work and is fundamentally based on the second law of thermodynamics.
Refrigeration system – It is a mechanical or thermodynamic equipment which abstracts heat from a low-temperature area and transfers it to a high-temperature area, thereby lowering and maintaining the temperature in the original area. This artificial cooling process typically involves a working fluid (refrigerant) which cycles through different phases and states, driven by components like a compressor and expansion valve, to absorb and release heat.
Refrigeration technology – It is the science and application of heat transfer to artificially cool a space or substance below the ambient temperature, typically by moving heat from a lower-temperature area to a higher-temperature environment using mechanical work. This involves the controlled circulation of a refrigerant through a refrigeration cycle, utilizing principles of thermodynamics, particularly the second law, to facilitate the transfer of heat through processes like compression, expansion, evaporation, and condensation.
Regasification – It is the process of converting liquefied natural gas (LNG) back into its gaseous state for distribution and use. This occurs at terminals where liquefied natural gas, after being transported in its liquid form (which is a much smaller volume), is reheated by heat exchangers using sources like warm water to evaporate it and prepare it for pipeline injection.
Regasification process – It is the controlled process of converting liquefied natural gas (LNG) back into its gaseous state by applying heat through heat exchangers, typically using sources like seawater or ambient air. This vaporized natural gas is then pressurized, frequently to over 8.5 mega-pascals, and can be supplied to pipelines for heating, electricity generation, or use as a vehicle fuel. The engineering challenges involve ensuring maximum safety because of the flammability of the liquefied natural gas and achieving high thermal efficiency in the heat exchangers to handle large volumes of gas efficiently.
Regeneration gas – It refers to the gas used to desorb impurities from molecular sieve beds in a regeneration circuit, where it is processed in a specific order, impacting the quality of the outlet gas.
Regeneration gas cooler – It is a component which cools the wet regeneration gas after it has been heated and used to desorb water and hydrocarbons from the adsorbent bed, facilitating the separation of condensed water and liquid hydrocarbons.
Regenerative braking – It is a braking scheme that returns energy to the source.
Regenerative Brayton cycle – It is an improved version of the Brayton cycle which incorporates a regenerator to preheat the pressurized air from the compressor, enhancing the cycle’s thermal efficiency by recovering waste heat from the exhaust gases. This cycle needs that the temperature at the turbine outlet be higher than that at the compressor exit to facilitate effective heat transfer.
Regenerative burner – A regenerative burner is with a heat recovery system that recovers the waste heat of the furnace exhaust gas to heat up the combustion air needed for the burning of the fuel at the burner. Use of regenerative burners for reheating furnaces can provide significant energy savings. The regenerative burners are designed to recover the heat to the inlet air by transferring the heat from the exhaust gas to the inlet air which is to be used in the combustion. The regenerative burner has two set of burners each with a regenerator and the reversing valve. The regenerator uses the ceramic (usually alumina) balls to collect the heat. While the first regenerative burner is firing, the other is exhausting the furnace gases. The exhaust gas is passed through the regenerative burner body and transfers the heat to the ceramic balls. Hence, the heat from exhaust gas is transferred to the inlet air since it is passed through the heated ceramic balls. The reversing valve sets the direction of the air flow that enters into the burner head, which makes the inlet air temperature similar to the operating temperature. Because of a high preheat combustion air temperature, the regenerative burner can save the fuel and make the combustion highly efficient.
Regenerative circuit – It is a circuit which uses positive feedback. It can be an amplifier or an oscillator.
Regenerative conveyor – It is a conveyor for which the head is at a substantially lower altitude than the tail (downhill conveying), generating power.
Regenerative heating – As in recuperative heating, waste heat from the furnace is used to pre-heat combustion air. Regenerative heating is a cyclic process whereby exhaust gases pass over and hence heat up refractory blocks in one of two pre-heating chambers. Once the first chamber has been heated up, exhaust gases are diverted to heat the second chamber, while cold combustion gas is introduced into the first chamber to be pre-heated by the hot refractory blocks. Continuous reversal of this process provides a permanent flow of pre-heated gas for combustion.
Regenerative process – It involves a system which recovers and reuses its own energy or components, frequently through cycles that repeat and are statistically similar to the beginning of the process. This concept applies in different contexts such as regenerative braking recovers mechanical energy during braking to convert it into electrical energy, recharging a battery, and regenerative cycles in industrial systems, like power plants, extract waste heat from different stages to improve overall efficiency.
Regenerative turbine pump – It is also known as drag, friction, liquid-ring pump, peripheral, traction, turbulence, or vortex pumps. These pumps are a class of rotodynamic pump that operates at high head pressures, typically 400 kilopascals to 2,000 kilopascals. The pump has an impeller with a number of vanes or paddles which spins in a cavity. The suction port and pressure ports are located at the perimeter of the cavity and are isolated by a barrier called a stripper, which allows only the tip channel (fluid between the blades) to recirculate, and forces any fluid in the side channel (fluid in the cavity outside of the blades) through the pressure port. In a regenerative turbine pump, as fluid spirals repeatedly from a vane into the side channel and back to the next vane, kinetic energy is imparted to the periphery, hence pressure builds with each spiral, in a manner similar to a regenerative blower. As regenerative turbine pumps cannot become vapour locked, they are normally applied to volatile, hot, or cryogenic fluid transport. However, as tolerances are typically tight, they are vulnerable to solids or particles causing jamming or rapid wear. Efficiency is typically low, and pressure and power consumption typically decrease with flow. Additionally, pumping direction can be reversed by reversing direction of spin.
Regenerator – It is same as recuperator except that the gaseous products or combustion heat brick checker work in a chamber connected to the exhaust side of the furnace while the incoming air and fuel are being heated by the brick checker work in a second chamber, connected to the entrance side. At intervals, the gas flow is reversed so that incoming air and fuel contact hot checker work while that in the second chamber is being reheated by exhaust gases. Regenerator is normally used for large capacity furnaces. In regenerator, a minimum of two chambers are used so that while one is absorbing heat from the exhaust gases, the other is transferring heat to the combustion air. The direction of air-flow is altered about a fixed interval of time. Important relations exist between the size of the regenerator, time between reversals, thickness of brick, conductivity of brick and heat storage ratio of the brick. The time between the reversals is an important aspect in a regenerator. Long periods mean higher thermal storage and hence higher cost. Also, long periods of reversal result in lower average temperature of preheat and consequently reduce fuel economy. Regenerators are especially suited for high temperature applications with dirty exhaust gases. The major disadvantages are its large size and the capital costs, which are significantly greater than costs of recuperators. Other disadvantages of regenerator are the accumulation of dust and slagging on the surfaces which reduce efficiency of the heat transfer. Heat losses from the walls of the regenerator and air in leaks during the gas period and out-leaks during air period also reduces the heat transfer efficiency.
Regime – It is a preferred state of the climate system, frequently representing one phase of dominant patterns or modes of climate variability.
Region – It is a territory characterized by specific geographical and climatological features. The environment and climate of a region is affected by regional and local scale forcing such as topography, land use characteristics, lakes, industries etc. as well as remote influences from other regions.
Regional grid – It is an interconnected network of power transmission lines, substations, and distribution systems which covers a specific geographic area, connecting local power generation and consumption within that region. It is a hierarchal level of the national electrical grid, designed to manage localized energy demands and resources, optimize power flow, and ensure the reliability and security of the electricity supply within the region by balancing power resources and managing peak demand periods.
Regional market – It is a designated geographic area or group of territories where goods and services are bought and sold, often defined by political, cultural, or economic boundaries, and characterized by shared characteristics. It is a broader concept than a local market, encompassing a specific geographic region for sales and distribution.
Regional metamorphism – It is the metamorphism caused by both the heat of igneous processes and tectonic pressure.
Regional vulnerability assessment (RVA) – It is a structured process to identify, analyze, and prioritize potential harms to a specific geographic area, frequently from environmental changes, societal pressures, or other hazards. It assesses the exposure of a region to risks, its sensitivity to potential impacts, and its capacity to adapt to them. Regional vulnerability assessments serve as early warning systems and planning tools, helping decision-makers understand future risks and develop strategies for risk mitigation and improved resilience.
Region of instability – Normally fan curves arc downward from the zero-flow condition, i.e., as the back-pressure on the fan decreases, the airflow increases. Majority of fans have an operating region in which their fan performance curve slopes in the same direction as the system resistance curve. A fan operating in this region can have unstable operation. Instability results from the fan’s interaction with the system as the fan attempts to generate more air flow, which causes the system pressure to increase, reducing the generated air flow. As the air flow decreases, the system pressure also decreases, and the fan responds by generating more air flow. This cyclic behaviour results in a searching action which creates a sound similar to breathing. This operating instability promotes poor fan efficiency and increases wear on the fan components.
Regranulation – It refers to the process of reusing internally generated scrap material by processing it, although the energy used in this processing is permanently lost. It emphasizes minimizing the quantity of material produced for regrinding before optimizing the regranulation method itself. In case of plastics, regranulation is the process of shredding plastic waste into small pieces, melting it, and then extruding it into uniform granules (pellets) which can be reused as a secondary raw material to make new plastic products. This process produces a consistent particle size and removes dust, making the recycled material suitable for further manufacturing and promoting a circular economy by reducing waste and the need for virgin plastic.
Regression analysis – It is a statistical method for modeling the relationship between a dependent variable and one or more independent variables, used to understand how changes in the independent variables affect the dependent variable, make predictions, and identify which factors are most influential. It establishes an equation which best fits the data, allowing for forecasting and the quantitative assessment of relationships between variables.
Regression coefficient – It is a statistical value which quantifies the average change in a dependent variable for a one-unit change in an independent variable, representing the slope of the regression line. These coefficients indicate the direction and magnitude of the relationship between variables, where a positive coefficient means the variables increase together, a negative coefficient means one increases as the other decreases, and a larger absolute value signifies a stronger relationship.
Regression model – It is a statistical tool which quantifies the relationship between a dependent variable and one or more independent variables, allowing for prediction of future outcomes and understanding the impact of those independent variables. For example, it can estimate how temperature (an independent variable) affects the expansion of mercury (a dependent variable) in a thermometer. Common types include linear regression for a straight-line relationship and logistic regression for predicting categorical outcomes, like predicting if an email is spam or not.
Regression technique – It is a statistical or data-driven method used to understand and quantify the relationship between a dependent variable and one or more independent variables, allowing for the prediction of the dependent variable’s value based on the independent variables. Basically, it finds a mathematical relationship or a pattern in data to make educated guesses or forecasts about future outcomes.
Regular castable – It is a refractory castable with a hydraulic bond containing cement but without a deflocculant and with a calcium oxide content higher than 2.5 % on a calcined basis.
Regular lay – Regular lay in the wire rope denotes that the wires are twisted in one direction, and the strand in opposite direction to form the rope. The wires in regular lay line up with the axis of the rope. The direction of the wire lay in the strand is opposite to the direction of the strand lay. Regular lay wire ropes are distinguished between right-hand ordinary lay (RHOL) and left-hand ordinary lay (LHOL). Due to the difference in direction between the wires and strand, regular lay ropes are less likely to untwist or kink. Regular lay roes are also less subject to failure from crushing and distortion because of shorter length of exposed outer wires. Regular lay ropes are naturally more rotation-resistant, and also spool better in a drum than lang lay ropes. The advantages of regular lay ropes are (i) better structural stability, (ii) higher number of broken wires is allowed, and (iii) identification of broken wires is easier.
Regular port valve – It is a term normally applied to plug valves. The regular port of such a valve is customarily around 40 % of the line pipe area. It corresponds to a venturi or reduced-bore valve of the same nominal pipe size. Venturi ball valves frequently are a logical alternative to plug valves with advantages in price torque and low maintenance.
Regular reflection – It is the condition in which all the incident light is reflected at the same angle as the angle of the incident light relative to the normal at the point of incidence. The reflection surface then appears bright, or mirrorlike, when viewed with the naked eye.
Regular spangle – They are visible multifaceted zinc crystal structure on zinc coated steel. The cooling rate is uncontrolled which produces a variable grain size.
Regulating pressure – It refers to the process of controlling and maintaining a fluid’s pressure at a desired level, frequently by reducing a high input pressure to a lower output pressure, using a device like a pressure regulator.
Regulating transformer – It is also known as a voltage regulator. It is a device which maintains a stable voltage output despite fluctuations in the input voltage or load, ensuring electrical equipment operates optimally. Originally, regulating transformers were installed in power systems to compensate for voltage fluctuations. However, studies have shown that they also have several other important advantages for transmission systems. By carefully choosing the transformation ratios, it is possible to control the active and reactive power flow in the power system to allow for a more economic utilization of the transmission capacity. In addition, the power losses associated with energy distribution can be considerably reduced and circulating currents largely avoided.
Regulating valve – It is also known as a control valve. It is a throttling valve which exercises automatic control over some variable (normally pressure). It is not an on-off valve. It is a device which is used to adjust and control the flow of fluids or gases by varying the size of the flow passage, hence enabling precise regulation of flow rate, pressure, temperature, or liquid level.
Regulation – It refers to statutory rules or laws which are formally written down and enacted by a legislative body, and have the force of law.
Regulations and standards – Regulations are mandatory, legally enforceable rules set by statutory or governmental authorities to ensure safety, protect interests, and maintain order, while standards are established norms, guidelines, or requirements for products, processes, or systems developed by consensus (frequently by industry bodies like International Organization for Standardization) to provide benchmarks for quality, consistency, and best practices. The key difference is that regulations are compulsory by law, whereas standards are typically voluntary unless incorporated into a regulation or contract.
Regulation system – It is a structured set of rules, standards, and mechanisms, typically established by an authority, to control, guide, or influence the behaviour of individuals, organizations, equipments, or processes to achieve specific goals. This system includes the creation of standards and statutory rules, monitoring for compliance, and enforcing penalties for violations.
Regulator – It is a device for controlling the delivery of welding or cutting gas at some substantially constant pressure.
Regulatory agencies – These are government authorities which establish and enforce laws and standards within specific sectors to protect the public interest, promote fair practices, and prevent failures and hazardous events. They function by setting regulations, licensing activities, conducting inspections, and taking corrective actions or penalties to ensure compliance with the statutory requirements.
Regulatory bodies – These are government agencies which regulates and enforces rules and regulations in a specific area.
Regulatory compliance – It is the process of adhering to laws, regulations, standards, and other rules set forth by governments and other regulatory bodies. It is an important aspect of organizational working, since organizations are required to follow certain laws and regulations to maintain their operations. Regulatory compliance helps ensure that organizations do not engage in unethical or illegal practices. The compliance standards are specific to industries and locations and can result in large penalties if not followed correctly.
Regulatory control – It refers to the government or regulatory body’s authority to oversee and enforce rules for an industry, system, or activity to ensure health, safety, economic stability, or environmental protection. This is achieved through the imposition of mandatory standards, laws, and regulations.
Regulatory instruments – These are rules-based tools which focus on enforcing compliance with minimum standards. Their goal is compliance with the law and their driving mechanism is deterrence. Regulatory tools include laws and regulations.
Regulatory norms – These are the norms which are legally binding rules and guidelines established by statutory authorities or regulatory bodies to control an industry, process, or sector, ensuring compliance and responsible conduct.
Regelation – It is the phenomenon in which ice converts to liquid because of the applied pressure and then re-converts to ice once the pressure is removed. It is the phenomenon of ice melting under pressure and refreezing when the pressure is reduced. This can be demonstrated by looping a fine wire around a block of ice, with a heavy weight attached to it. The pressure exerted on the ice slowly melts it locally, permitting the wire to pass through the entire block. The wire’s track refills as soon as pressure is relieved, so the ice block will remain intact even after wire passes completely through. This experiment is possible for ice at −10 deg C or cooler, and while essentially valid, the details of the process by which the wire passes through the ice are complex. The phenomenon works best with high thermal conductivity materials such as copper, since latent heat of fusion from the top side needs to be transferred to the lower side to supply latent heat of melting.
Rehabilitation – It is a treatment or treatments designed to facilitate the process of recovery from injury, illness or disease to as normal a condition as possible.
Rehbinder effect – It is the modification of the mechanical properties at or near the surface of a solid, which is attributable to interaction with a surfactant.
Reheading machines – These machines are used when the work-piece is needed to be annealed before heading is completed. As an example, when the quantity of cold working needed cause the work-piece to fracture before heading is complete. Reheading machines are made as either open-die or solid-die machines, single or double stroke, and can be fed by hand or hopper. Punch presses are also used for reheading.
Reheat behaviour – It consists of the changes in length or volume which are taking place in a fired refractory when subjected to a reheat test.
Reheat change (after shrinkage and after expansion) – After heating to high temperature and subsequent cooling, a permanent change in the dimension (permanent linear change) frequently occurs which is described as after expansion or after shrinkage. If a refractory brick has very strong after-shrinkage then the joints get enlarged and the brickwork is loosened and no longer tight. In opposite case, after expansion is also dangerous since this can cause the destruction of the brickwork through pressure. The permanent linear change (PLC) of the refractories can be influenced. For getting a brick with a constant volume, the burning of the raw materials and the firing of the bricks is to be controlled in such a manner so that equilibrium is achieved at the desired temperature.
Reheating furnace – It is one of the key equipments in a hot rolling mill. It consumes the majority of energy needed for the rolling of steel. It is normally used to heat the steel stock (billets, blooms, or slabs etc.) to the rolling temperatures which are suitable for plastic deformation of steel and hence for rolling in the hot rolling mill. Reheating furnace is an important equipment for the hot rolling of steel. It is the heart of any hot rolling mill. The heating process in a reheating furnace is a continuous process. Fuel used in these furnaces can be pulverized coal, liquid fuel, or gaseous fuel. Types of the reheating furnaces used in the rolling mills are (i) pusher furnace, (ii) walking beam furnace, (iii) walking hearth furnace, (iv) roller hearth furnace, and (v) rotary hearth furnace. The rotary hearth furnace is normally used in pipe rolling mills. The steel stock to be rolled is charged at the entrance of the reheating furnace. During its travel in the reheating furnace, the steel stock is pre-heated, heated, and soaked as it passes through pre-heating, heating and soaking zone of the reheating furnace. At the end of the soaking zone of the furnace, the steel stock is discharged from the furnace by ejector for rolling in the rolling mill. The temperature of the heated steel material at the time of discharged depends on several factors and it can vary in the range of 1,100 deg C to 1,250 deg C.
Reheat steam cycle – It is a Rankine cycle modification where steam is partially expanded through a high-pressure turbine, then sent back to the boiler to be reheated before continuing expansion in a low-pressure turbine. This process improves the thermal efficiency by increasing the mean temperature of heat addition and significantly reduces the ‘wetness’ (moisture content) in the exhaust steam, which helps to prevent erosion of the low-pressure turbine blades.
Reheat test – It is the prescribed heat treatment of a fired refractory free of externally applied stresses to determine its linear or volume stability by measurements before and after the heating.
Reheat turbines – These turbines are used almost exclusively in electrical power plants. In a reheat turbine, steam flow exits from a high-pressure section of the turbine and is returned to the boiler where additional superheat is added. The steam then goes back into an intermediate pressure section of the turbine and continues its expansion.
Reichert cones – These are essentially an improved version of the trays. They are cone-shaped with a central single feed point. Normally, they contain multiple stages mounted vertically above each other. The more common configurations are (i) 4DS (four double / single stages), and (ii) 2DSS.DS (two double / single / single stages plus a double /s ingle stage), the first one is used as the roughers while the second as the cleaners. The process variables are (i) feed rate (increased rate reduces performance above an optimum), (ii) feed density (needs to be kept between 60 % to 63 % solids otherwise either recovery or grade suffers), and (iii) insert settings (range 1 to 9 with increasing opening the recovery is more but the grade gets lower). The advantages are (i) high capacity for floor area, and (ii) high feed density (63 % solids) so low volume-pumping needed. The disadvantages are (i) low upgradation ratio (typically 3:1), (ii) controlled specific gravity of the feed is needed, (iii) low recovery of fines, (iv) feed needs screening, (v) low tolerance for slimes, (vi) bottom separating surfaces of cones not visible or easily accessible, and (vii) needs wash water for density control during cleaner stages.
Reinforced composite material – It is a composite consisting of a matrix material and reinforcing agents, typically high-strength fibres, particles, or fabrics which improve the composite’s mechanical properties, such as strength, stiffness, and rigidity. The matrix binds these reinforcements together, distributes stress, and protects them from damage, creating a strong, lightweight material with properties superior to its individual components.
Reinforced composite structure – It is a composite material where a matrix (like a plastic, metal, or ceramic) is strengthened by embedding fibres or particles of another material, providing improved mechanical properties like increased strength, stiffness, and impact resistance compared to the individual components alone. The fibres or particles act as the ‘reinforcement’, distributing stress and preventing the matrix from failing, while the matrix holds the reinforcement in place and provides toughness.
Reinforced concrete – It is a composite material in which concrete’s relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is normally, though not necessarily, steel reinforcement bars (abbreviated as rebar) and is normally embedded passively in the concrete before the concrete sets. However, post-tensioning is also employed as a technique to reinforce the concrete. In corrosion engineering terms, when designed correctly, the alkalinity of the concrete protects the steel rebar from corrosion.
Reinforced concrete beam – It is a structural element made from a combination of concrete and steel reinforcement bars (rebar) to carry loads, mainly bending moments and shear forces. Concrete excels in compression but is weak in tension, while steel provides the necessary tensile strength to the composite material, creating a strong and durable beam widely used in buildings, bridges, and other structures.
Reinforced concrete structure – It is a composite building material which combines concrete with steel reinforcement (rebar), creating a stronger, more durable, and more versatile material than either concrete or steel alone. The concrete provides high compressive strength, while the embedded steel provides high tensile strength, allowing the structure to effectively withstand both pushing and pulling forces, making it ideal for buildings, bridges, and dams
Reinforced concrete structures drawing – The two main groups of drawings for showing reinforced concrete structures are general arrangement drawings, and reinforcement drawings. General arrangement drawings are floor plans, roof plans, sections and elevations, drawn to a small scale and provide overall view of the work. They supply the setting out dimensions, the positions and sometimes the sizes of all the members. A reference grid is provided similar to that for a structural steel building.
Reinforcement drawings of structural elements are drawn to a larger scale and give detailed information about the reinforcement. There is no justification for ambiguity, and it is necessary that all drawings are easy to read, and cannot be misunderstood.
Reinforced material – It is a base material improved by the addition of another material (the reinforcement) to improve its mechanical properties, such as strength, stiffness, or toughness. Reinforcements are frequently in the form of fibres, particulates, or whiskers and are integrated into a surrounding ‘matrix’ material, creating a composite which performs better than the original material alone.
Reinforced membrane – It is a membrane improved with stronger, more durable materials, like fibres, fabrics, or polymers, to improve its mechanical strength, flexibility, and overall integrity. This combination creates a composite structure where the reinforcement material provides stability and resistance, allowing the membrane to withstand greater stress and pressure while frequently maintaining its essential membrane properties, such as conductivity or permeability.
Reinforced plastics – These are moulded, formed, filament- wound, tape-wrapped, or shaped plastic parts consisting of resins to which reinforcing fibres, mats, fabrics, and so on, have been added before the forming operation to provide some strength properties greatly superior to those of the base resin.
Reinforced polymer – It is also known as fibre-reinforced polymer or fibre-reinforced plastic. It is a composite material which is made of a polymer matrix reinforced with fibres. The fibres are normally glass, carbon, or aramid, although other fibres such as paper or wood or asbestos have been sometimes used. The polymer is normally an epoxy, vinylester or polyester thermosetting plastic. Phenol formaldehyde resins are still in use.
Reinforced reaction injection moulding (RRIM) – It is a reaction injection moulding with a reinforcement added.
Reinforcement – It is a strong material bonded into a matrix to improve its mechanical properties. Reinforcements are normally long fibres, chopped fibres, whiskers, particulates, and so on. The is not to be used synonymously with filler.
Reinforcement bar – It is also called reinforcing bar, rebar, reinforcing steel or steel reinforcement. It is a tension device which is added to concrete to form reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. Concrete is strong under compression, but has low tensile strength. Rebar normally consists of steel bars which significantly increase the tensile strength of the structure. Reinforcement bar surfaces feature a continuous series of ribs, lugs, or indentations to promote a better bond with the concrete and reduce the risk of slippage. The most common type of reinforcement bar is carbon steel, typically consisting of hot-rolled round bars with deformation patterns embossed into its surface. Steel and concrete have similar coefficients of thermal expansion, so a concrete structural member reinforced with steel experiences minimal differential stress as the temperature changes.
Reinforcement corrosion – It is the deterioration of steel reinforcement bats embedded in concrete, caused by the loss of concrete’s protective alkaline environment because of the carbonation or the penetration of chloride ions. This chemical process forms rust, a larger volume product which generates internal pressure, leading to cracks and reduced structural integrity and load-bearing capacity in the concrete structure.
Reinforcing fillers – These are materials incorporated into a rubber matrix which improve mechanical properties such as tensile strength, modulus, abrasion resistance, hardness, and tear resistance. They are characterized by factors including particle size, structure, concentration, physical and chemical nature, and porosity, with examples including carbon black and precipitated silica.
Reinforcing material – It is defined as substances added to plastics to modify material properties, normally in the form of fibres or particulate fillers, which improve the mechanical performance of composites by improving strength and stiffness.
Reinforcing material lay-up quality control – It refers to the processes and procedures which are used to ensure the quality and integrity of a composite material’s structure during the layering (lay-up) of reinforcing materials (like fibres) and resin, critical for achieving desired mechanical properties.
Reinforcing mechanism – It refers to the processes by which carbon nano-tubes (CNTs) and carbon nano-fibres (CNFs) improve the mechanical performance of cement-based materials through effects such as filling, bridging, and nucleation, which contribute to reduced porosity, improved crack resistance, and enhanced crystallinity of binding materials.
Reinstatement – It refers to the act of restoring someone or something to a former position, status, or condition.
Reject rate – It is the percentage of units produced which are considered defective or substandard. A lower Reject rate implies a higher-quality manufacturing process with fewer defective units being produced. Rejection rate is ratio of the number of parts scrapped to the total number of parts manufactured, expressed as a percentage.
Relative atomic mass – It is defined as a dimensionless number which indicates how many times the atomic mass of an atom is higher than the atomic mass unit (AMU). It corresponds numerically to the molar mass expressed in grams per mole.
Relative biological effectiveness (RBE) – It is the ratio of the dose of a reference radiation (like X-rays) to the dose of another radiation needed to produce the same biological effect. It essentially quantifies how much more effective one type of radiation is compared to another in causing a specific biological outcome.
Relative cost coefficients – These are defined as a measure used to evaluate the increased cost of producing a component with specific characteristics compared to an ideal design, taking into account factors such as material-process compatibility, geometry, size, tolerances, and surface finish. Each coefficient reflects the relative cost impact of deviations from ideal conditions, with a value of unity indicating an ideal design.
Relative density – It is also called specific gravity. It is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Relative density for solids and liquids is nearly always measured with respect to water at its densest (at 4 deg C) and for gases, the reference is air at room temperature (20 deg C). The term ‘relative density’ is preferred in International System of Units, whereas the term ‘specific gravity’ is gradually being abandoned.
Relative density distribution – It refers to the variation of density within a material, which can show differences in density across different areas, particularly during processes such as compaction, where a more homogeneous density is desirable
Relative erosion factor – It refers to a factor which quantifies the influence of specific factors (like rainfall, soil type, topography, or land management) on the rate of soil erosion, compared to a baseline or standard condition.
Relative flow coefficient – It is the ratio of the flow coefficient at a stated travel to the flow coefficient at rated travel.
Relative humidity – It is the ratio of partial density of water vapour in the air to the saturation density of water vapour at the same temperature. It is the ratio of the mass of water vapour present in a unit volume of gas to the maximum possible mass of water vapour in unit volume of the same gas at the same temperature and pressure.
Relative operating characteristic (ROC) curve – It is a graphical representation of a classifier’s performance, plotting the true positive rate (sensitivity) against the false positive rate (1-specificity) across different threshold settings, allowing for the visualization of trade-offs between sensitivity and specificity.
Relative permeability – It is the ratio of effective permeability to absolute permeability, indicating the ability of a porous medium to allow fluid flow in the presence of other fluids. This dimensionless parameter ranges from 0 to 1 and is influenced by factors such as rock wettability and saturation history.
Relative potency factor (RPF) – This factor quantifies potencies of substances with respect to a defined effect, relative to the potency of a chosen index substance. Relative potency factors can be used to express combined exposures of multiple substances in terms of the exposure value of the chosen index substance (i.e., in index substance equivalents). Hazard characterizations, and hence also relative potency factors are based on mass units (e.g., micrometers), and not on mol units. Relative potency factors can be different for different levels of the human organism (external, internal, specific compartment). These factors can be given as data or computed from hazard characterizations. These factors can be specified with uncertainty. Computation from uncertain hazard characterizations allows to include correlations between uncertain relative potency factors which originate from using the same index substance.
Relative rib area – It is also known as bond index. It is a measure used in concrete construction for steel reinforcement bars. It is defined as the ratio of the total projected area of the ribs onto a plane perpendicular to the bar’s axis to the bar’s nominal surface area between two ribs. It quantifies the bar’s surface roughness and is a key parameter influencing the bond strength between the reinforcement bar and the surrounding concrete, as a higher relative rib area normally leads to increased bond strength.
Relative sea level (RSL) – It is defined as the sea level which is observed with respect to a land-based reference frame. It is frequently contrasted with eustatic sea level, which is a measure of the total mass or volume of the oceans. Relative sea level can change by the processes changing eustatic sea level (e.g., ice melt and thermal expansion), but also by changes on land such as subsidence and isostatic rebound. In sequence stratigraphy, relative sea level is similarly defined as the distance from the ocean surface to the bottom of the sediment on the ocean floor. Hence, relative sea level is independent of the thickness of the sediment layer at the bottom of the ocean, which makes it a different concept than water depth.
Relative sintering temperature – It is the ratio of the sintering temperature to the melt ing temperature of the substance as expressed on the Kelvin scale. It refers to the sintering temperature expressed as a percentage of the material’s melting point, typically between 60% and 80% of the melting temperature, to achieve optimal densification and bonding.
Relative speed – ItvB∣A=‖vB∣A‖ is the vector norm of the relative velocity. It is the speed of one object in relation to another. It is used to compare the speeds of two or more objects moving at different rates.
Relative standard deviation (RSD) – It is the standard deviation expressed as a percentage of the mean value given by RSD = 100 (S/X) [Dsquare/(n-1)], where ‘S’ is the standard deviation, ‘D’ is the difference between individual results and the average, ‘n’ is the number of individual results, and ‘X’ is the average of individual results. It is also known as coefficient of variation.
Relative steam velocity – It refers to the velocity of steam as seen by a moving blade, rather than a stationary observer. It is a crucial concept in understanding turbine performance and design.
Relative thermal index (RTI) – It is a measure of a material’s ability to retain its properties when exposed to high temperatures over an extended period, indicating its thermal endurance. It is a characteristic parameter which reflects a material’s resistance to thermal degradation, specifically its ability to maintain its physical and / or electrical properties under high-temperature conditions. Relative thermal index is determined by subjecting a material to a series of progressively higher temperatures and measuring its properties at each temperature. A higher value of relative thermal index indicates a material’s better ability to withstand high temperatures without significant degradation of its critical properties.
Relative transmittance – It is the ratio of the transmittance of the object in question to that of a reference object. For a spectral line on a photographic emulsion, it is the ratio of the transmittance of the photographic image of the spectral line to the transmittance of a clear portion of the photographic emulsion. Relative transmittance can be total, specular, or diffuse.
Relative units, temperature – Relative units are compared with a physical and chemical process which always produces the same temperature. Degrees Celsius (international system), also called degrees centigrade and represented by the symbol ‘degree C’. This measurement unit is defined by assigning the value 0 degree to the freezing point of water and the value 100 degree to the boiling point of water when both measurements are taken at a pressure of one atmosphere. The scale is then divided into 100 equal parts in which each corresponds to 1 degree. Degrees Fahrenheit (international system) measurement unit is based on divisions between the freezing and evaporation points of ammonium chloride solutions. In this scale, the zero and hundred corresponds to the freezing and evaporation temperatures of ammonium chloride in water. As per this scale 32 degrees Fahrenheit corresponds to the melting point of ice and 212 degrees Fahrenheit corresponds to boiling point of water. The difference between the two points is 180 degrees which is divided into 180 equal portions, determines the degree Fahrenheit.
Relative velocity – It is the velocity of an object ‘B’ relative to another object ‘A’ is the velocity which the object ‘B’ appears to have to an observer moving with ‘A’. The relative velocity of an object ‘B’ relative to an observer ‘A’, is the velocity vector of ‘B’ measured in the rest frame of ‘A’.
Relativistic heavy ion collider (RHIC) – It is a particle accelerator which collides beams of heavy ions (like gold) at nearly the speed of light to study the fundamental forces and properties of matter, including the creation and properties of a state of matter called quark-gluon plasma.
Relaxation curve – It is a plot of either the remaining, or relaxed, stress as a function of time.
Relaxation oscillator – It is an oscillator which relies on an active device periodically changing state. Such oscillators normally produce a square-wave or sawtooth waveform, different from the approximately sinusoidal waveshape of a harmonic oscillator.
Relaxation rate – It is the absolute value of the slope of a stress-relaxation curve at a given time.
Relaxation time – It is the time needed for a stress under a sustained constant strain to diminish by a stated fraction of its initial value.
Relaxed stress – It is the initial stress minus the remaining stress at a given time during a stress-relaxation test.
Relay – It is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch can have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof. Relays are used where it is necessary to control a circuit by an independent low-power signal, or where several circuits are to be controlled by one signal.
Relay contacts – These refer to the conductive components within a relay which open or close a circuit in response to the movement of the armature, which is actuated by a magnetic field generated by a small current in the solenoid. When the armature is attracted, the relay contacts allow a much larger current to flow, enabling the control of high-power devices.
Release – A release occurs when a hazardous substance goes from a controlled condition (for example, inside a truck, barrel, storage tank, or landfill) to an uncontrolled condition in the air, water, or land.
Release agent – It is a material which is applied in a thin film to the surface of a mould to keep the resin from bonding to the mould. It is also called parting agent. It is also called parting agent. Release agent is a material, e.g., silicone, stearate, oil, or wax for lubricating a die pattern or core box to facilitate easy removal of a casting, mold or core.
Release film – It is an impermeable layer of film which does not bond to the resin being cured.
Release paper – It is a sheet, serving as a protectant or carrier, or both, for an adhesive film or mass, which is easily removed from the film or mass prior to use.
Reliable data – It means that data which can be trusted to be accurate, complete, consistent, and free from errors, ensuring that it is trustworthy and can be used confidently for decision-making.
Reliability – It is the probability which an item survives a given operating period, under specified operating conditions, without failure. It is a quantitative measure of the ability of a product or service to fulfill its intended function for a specified period of time. It is defined as the probability which a product, system, or service performs its intended function adequately for a specified period of time, or operates in a defined environment without failure. Reliability is closely related to availability, which is typically described as the ability of a component or system to function at a specified moment or interval of time. Reliability frequently plays a key role in the cost-effectiveness of systems.
Reliability analysis – It is a process for measuring how consistent and dependable a system, product, or scale is over time or under repeated conditions. It assesses a product’s ability to function as intended without failure for a specified duration. In statistics and research, it evaluates whether a measurement tool consistently yields similar results when used repeatedly, ensuring the scores are not random.
Reliability assessment – It evaluates a measurement instrument’s ability to produce consistent and stable results when used repeatedly under similar conditions. Instruments like thermometers or assessments are reliable if they yield the same outcome each time they are applied, suggesting a lack of random error. The assessment of reliability typically involves comparing results from the same instrument over different times (test-retest), by different individuals (interrater), or assessing the consistency of items within the instrument itself (internal consistency).
Reliability centered maintenance (RCM) – It is a process used to determine what must be done to ensure that any physical asset continues to function in order to fulfill its intended functions in its present operating context. It is a method to identify and select failure management policies to efficiently and effectively achieve the required safety, availability and economy of operation. It is a process to establish the safe minimum levels of maintenance while ensuring an equipment continues to perform to its design function within the current operating context. It achieves this by providing a means for determining optimal maintenance and operational strategies based on the probability and consequence of the analyzed failure modes. It is a systematic approach to determine the maintenance requirements of plant and equipment in its operation. It uses preventive maintenance, predictive maintenance, real-time monitoring, and run to failure and proactive maintenance. These techniques are used in an integrated manner to increase the probability which a machine or component is going to function in the required manner over its design life cycle with a minimum of maintenance. The aim of reliability centered maintenance is to create such maintenance strategy which helps minimize the total operating costs while increasing reliability of the system. Reliability centered maintenance basically combines several well-known techniques and tools, in a systematic approach managing risks, as a basis for maintenance decisions.
Reliability engineering – It is a sub-discipline of systems engineering which emphasizes the ability of equipment to function without failure. Availability, testability, maintainability, and maintenance are frequently defined as a part of ‘reliability engineering’ in reliability programmes.
Reliability factor – It is a value which quantifies the degree to which a product, component, or system performs its intended function under specified conditions for a given period of time. This factor can serve several purposes such as (i) in engineering, it’s a design factor to account for material uncertainties, ensuring the design meets a reliability goal, and (ii) in statistics, it is a factor from a distribution (like the t-distribution) used to calculate the margin of error in a confidence interval.
Reliability function – It is theoretically defined as the probability of success. In practice, it is calculated using different techniques, and its value ranges between 0 and 1, where 0 indicates no probability of success while 1 indicates definite success. This probability is estimated from detailed (physics of failure) analysis, previous data sets, or through reliability testing and reliability modeling.
Reliability indicator – It is a measurable quantity or metric used to assess the ability of a component, system, or data set to perform its intended function or to provide consistent results over time. Basically, it quantifies the dependability or consistency of something, helping to classify it as reliable or unreliable.
Relief radius – It refers to the radius of the rounded corners or edges of the roll grooves, designed to facilitate metal flow and prevent jamming or sticking during the rolling process.
Relief device – It is an emergency system component designed to discharge gas or fluid from a pressurized vessel or piping system to prevent a dangerous overpressure situation from exceeding its maximum allowable working pressure. These devices typically activate automatically when internal pressure reaches a predetermined level, releasing the excess fluid and then closing once pressure normalizes, hence protecting personnel and equipment from damage and potential explosions.
Relief grooves – These refer to circumferential grooves or notches, such as U-shaped notches, used in engineering design to reduce stress concentrations and improve stress flow in components, thence improving their mechanical performance.
Relief header – It is a large-diameter pipe in an industrial facility which collects gases, vapours, or liquids from multiple pressure relief devices, such as relief valves and rupture disks, and directs them to a central disposal point, such as a flare stack or knockout drum. Its main purpose is to safely manage overpressure events by ensuring that the released fluids are handled without creating excessive back pressure or forming dangerous pockets, frequently by maintaining a self-draining slope away from the relief devices.
Relief response – It is also known as emergency management. It is the generic name of an inter-disciplinary field dealing with the strategic organizational management processes used to protect critical assets of the organization from hazard risks which can cause disasters or catastrophes and to ensure their continuance within their planned lifetime.
Relief sprue – It is the term which normally refers to a second sprue at opposite end of the runner to relieve pressure created during pouring operation.
Relief valve – It is also known as pressure relief valve (PRV). It is a type of safety valve which is used to control or limit the pressure in a system since excessive pressure can otherwise build up and create a process upset, instrument or equipment failure, explosion, or fire.
Relief valve, safety relief valve – It is a quick-acting, spring-loaded valve which opens (relieves) when the pressure exceeds the spring setting. It is frequently installed on the body cavity of ball and gate valves to relieve thermal overpressure in liquid services. It is an automatic pressure relieving device actuated by the pressure upstream of the valve and characterized by opening pop action with further increase in lift with an increase in pressure over popping pressure.
Relieving – It is the buffing or other abrasive treatment of the high points of an embossed metal surface to produce highlights which contrast with the finish in the recesses. It is also the removal of material from selected portions of a coloured metal surface by mechanical means to achieve a multi-coloured effect.
Relubrication – It is the process of applying compatible grease to shielded bearings at recommended intervals to ensure their optimal performance and longevity.
Reluctance motor – It is a type of electric motor which induces non-permanent magnetic poles on the ferro-magnetic rotor, relying on varying magnetic reluctance. The rotor carries no windings.
Reluctance torque – It is the torque produced in a reluctance motor because of the tendency of the rotor to align itself with the magnetic field generated by the stator. This action occurs as the rotor positions itself to minimize reluctance within the magnetic circuit.
Remainder – It is the quantity ‘left over’ after performing some computation. In arithmetic, the remainder is the integer ‘left over’ after dividing one integer by another to produce an integer quotient (integer division). In algebra of polynomials, the remainder is the polynomial ‘left over’ after dividing one polynomial by another.
Remaining stress – It is the stress remaining at a given time during a stress-relaxation test.
Remanence (Br) – It is the magnetic induction remaining in a magnetic circuit after removal of the applied magnetizing force. It is sometimes called remanent induction. It is the force the electromagnet uses to hold the ferromagnetic piece after cancelling the magnetic field. Its approximate value is 5 % of holding force (Fm) depending on the piece (size, roughness, and material etc.).
Remanufacture – It is a form of green design in which parts and components are rebuilt or refurbished after a portion of their life so that they can be reissued and used as essentially new parts.
Remanufacturing – It is a comprehensive disassembly and reassembly process which restores a used product to at least its original equipment specified state, involving thorough cleaning, testing, diagnosis, and potential repair or replacement of worn or obsolete components. This process can include hardware upgrades and software changes, resulting in products that share capabilities equivalent to current production models.
Remedial action – It is the action which is taken to investigate, monitor, assess and evaluate the release or threat of release of hazardous substances or contaminants to the environment. It can also refer to the actual ‘clean-up’ of the environment by the different removal, treatment, monitored remediation, or corrective actions. The term clean-up is sometimes is used interchangeably with the terms remedial action, removal action, response action, remedy, remediation, or corrective action.
Remedial investigation (RI) – It establishes (i) the nature and extent of the contamination and the sources, (ii) identifies current and potential impacts to public health, welfare, and the environment, (iii) identifies current and reasonably foreseeable uses of land and waters of the state, and (iv) gets and evaluates any information necessary for identification and comparison of alternative remedial actions.
Remedial maintenance – It is a set of activities which are performed to eliminate the source of failure without interrupting the continuity of the production process.
Remedial measures – These refer to recommendations made to reduce risks associated with installations, which can include strategies such as nitrogen blanketing, bund provision, and installation of isolation valves to improve safety and mitigate potential hazards.
Remedial objective (RO) – It establishes remedial goals for the current and reasonably foreseeable uses of lands and waters of the region which have been or are threatened to be affected by a release of hazardous substance.
Remediation – It is a general term for providing a remedy. Environmental remediation deals with the clean-up, or other methods to contain pollution, toxic spills, hazardous materials, or contaminants from soil, groundwater, sediment, or surface water etc. for the general protection of human health and the environment.
Remediation (or Reclamation), mineral deposits – Remediation (or Reclamation) is the restoration of a Project site conditions which are required by regulatory or other provisions.
Remelt – It refers to either the process of melting metal again (re-melting) or the scrap metal which is melted again. Specifically, it includes returns like rejected castings, gates, sprues, and risers which are recycled by being added back into a new batch of molten metal to produce more ingots or castings. This remelting improves material quality and properties, making it a valuable and environmentally sound practice.
Remnant magnetization – It is the magnetization remaining in a magnetic material after the external magnetic field that produced it has been removed. It is a residual magnetic property, contrasted with induced magnetization which exists only when a field is present. This retained magnetism is also a quantitative measure of the magnetism left behind and can provide information about the history of the earth’s magnetic field, as seen in natural remanent magnetization in rocks.
Remote access – It is the ability to connect to and control a computer, network, or system from a different physical location, allowing users to work with files, applications, and data as if they are physically present.
Remote control – It is the operation of a valve or other flow-control device from a point at a distance from the device being controlled. It can be accomplished by electrical, pneumatic, or hydraulic means.
Remote-field eddy current (RFEC) inspection – It is a non-destructive examination technique which is suitable for the examination of conducting tubular goods using a probe from the inner surface. Because of the remote-field eddy current, the technique provides what is, in effect, a through-wall examination using only the interior probe. Although the technique is applicable to any conducting tubular material, it has been primarily applied to ferro-magnetics since conventional eddy current testing techniques are not suitable for detecting opposite-wall defects in such material unless the material can be magnetically saturated. In this case, corrosion / erosion wall thinning and pitting as well as cracking are the flaws of interest. One advantage of remote-field eddy current inspection for either ferro-magnetic or non-ferromagnetic material inspection is that the probe can be made more flexible than saturation eddy current or magnetic probes, hence facilitating the examination of tubes with bends or diameter changes. Another advantage of remote-field eddy current inspection is that it is approximately equal (within a factor of 2) in sensitivity to axially and circumferentially oriented flaws in ferro-magnetic material. The major disadvantage of remote-field eddy current inspection is that, when applied to non-ferromagnetic material, it is not normally as sensitive or accurate as traditional eddy current testing techniques.
Remote monitoring – It is the act of observing, checking, and managing a system, or a device from a different location using technology like IoT (Internet of Things), networks, and cloud computing to ensure optimal performance. This allows for real-time data collection, early detection of problems, proactive maintenance, and timely intervention, reducing downtime and improving efficiency.
Remote racking system – It is a system for inserting circuit breakers into switchgear which allows the operator to stay at a safe distance from any possible arc hazard.
Remote sensing – It is the small scale or large-scale acquisition of information of an object or phenomenon by the use of either recording or real-time sensing device(s) which are wireless, or not inphysical or intimate contact with the object (such as by way of aircraft, spacecraft, satellite, buoy, or ship). In practice, remote sensing is the stand-off collection through the use of a variety of devices for gathering information on a given object or area.
Remote sensor – It is a device which gathers information about an object or phenomenon from a distance, without direct physical contact, by collecting and measuring electro-magnetic radiation or other energy. These sensors can be passive, detecting natural energy, or active, emitting their own energy to illuminate a target and then measure the reflected energy. Examples include instruments which measure temperature or soil moisture.
Removable fasteners – It is a type of fastener which permits the parts to be readily disconnected without damaging the fastener, e.g. nut and bolt.
Removal action – It is an immediate, short-term clean-up action to address a release or threatened release of hazardous substances. This action is initiated to reduce or eliminate an immediate threat to public health and / or the environment.
Removal of minerals – This step is done to the clean water (from previous step) to remove minerals which can build-up on steam turbines or other process equipment. Depending on the water source, this step can be done by one or more of these processes (i) softening, (ii) demineralization (ion exchange), and (iii) reverse osmosis (membrane).
Removal of nitrogen oxides (NOx) – It refers to different methods and processes used to eliminate harmful nitrogen oxides, mainly nitrogen mono-oxide (NO) and nitrogen di-oxide (NO2) from gas streams, such as flue gas, by converting them into less harmful substances, like nitrogen gas (N2) and water. This is typically achieved through techniques like ‘selective catalytic reduction’ (SCR), which uses catalysts and a reducing agent like ammonia (NH3) to convert NOx into nitrogen and water, or through absorption and biological processes.
Removal of oxygen – Dissolved oxygen and other gases primarily consisting of carbon di-oxide (CO2) in boiler feedwater is major cause of boiler system corrosion. While oxygen results in localized corrosion (pitting), CO2 forms carbonic acid and damages condensate piping. Removal of oxygen can be done by (i) deaeration, or (ii) oxygen scavenging.
Renewable electricity – It is the electric power which is derived from primary energy sources that replenish on a rapid scale or that are not appreciably diminished by human exploitation.
Renewable energy – It is also called green energy. It is the energy made from renewable natural resources which are replenished on a human timescale. The most widely used renewable energy types are solar energy, wind power, and hydropower. Bioenergy and geothermal power are also significant in some countries. Some also consider nuclear power a renewable power source, although this is controversial, as nuclear energy requires mining uranium, a non-renewable resource. Renewable energy installations can be large or small and are suited for both urban and rural areas.
Renewable energy power generation – It is the production of electricity from natural, self-replenishing resources like sunlight, wind, water (hydropower), biomass, and geothermal heat which are naturally renewed at a rate faster than they are consumed. These sources are considered ‘green’ or clean energy since they have a low or zero-carbon footprint and considerably reduce harmful emissions, helping to combat climate change.
Renewable energy storage (RES) – It refers to systems which store energy produced from renewable sources, such as solar, wind, and biomass, to balance energy production with consumption. These systems, including batteries and pumped hydroelectric storage, address the challenges of intermittent energy supply and variability in electricity demand.
Renewable liquid fuels – These are defined as energy-dense fuels which are miscible with petroleum gasoline and diesel, providing a means to improve renewable energy content in the transport sector while potentially reducing greenhouse gas emissions.
Renewable natural gas (RNG) – It is anaerobically generated biogas which has been refined for use in place of fossil natural gas, sourced from materials such as municipal solid waste landfills, wastewater treatment plants, and organic waste management operations.
Reoil – It means oil put on the sheet after cleaning and before coiling for shipment to prevent water stain.
Reoxidation – It refers to the unwanted reaction of reactive elements in molten steel with air, leading to the formation of exogenous inclusions which can degrade product quality. This process can occur at different points in the steelmaking process where the melt is exposed to the atmosphere, particularly at uncovered surfaces in the ladle furnace, tundish, or continuous casting mold.
Reoxidation products – These are the inclusions because of reoxidation of steel. Example of such inclusion is the alumina inclusion generated when (i) the aluminum remaining in the liquid steel is oxidized by iron oxide in the slag, or (ii) by the exposure of the liquid steel to the atmosphere.
Repair – It means responding to the breakdown of equipment and undertaking work to correct the problem in order to return the equipment to a working condition. It is also performing finishing work on the piece after galvanizing in order to meet standards or specifications, or coating areas of steel which have been exposed because of the post galvanizing fabrication, installation, or extremely rough handling.
Repair engineering – It needs a thorough understanding of composite structural mechanics and structural joining of composites and metal structures. These two aspects, in combination with other considerations, such as damage removal, surface preparation, and repair fabrication, need a clearly defined engineering process. The level of repair is to be determined by such factors as damage criticality, operational requirements, and repair station capabilities. All of these add up to a unique repair for most composite structural damage restoration.
Repair technology – It refers to methods and processes used to restore damaged components, such as dies and moulds, enabling them to be put back into operation. Common techniques include different welding processes, such as tungsten inert gas welding, plasma arc welding, and laser welding, as well as alternative methods like electro-spark and cold-spray technologies.
Repair welding – It is the process of using different welding techniques to fix defects, damage, or worn components, restoring their original integrity and mechanical properties by removing the damaged area and depositing filler material. It is a critical step for maintaining the functionality and safety of structures and equipment, frequently involving careful preparation, the chosen welding process, and post-weld treatments like heat treatment to reduce stress and refine the material’s micro-structure.
Repassivation – It is the process where a passive oxide layer reforms on a metal surface after being damaged or temporarily removed, restoring its natural corrosion resistance. This occurs when aggressive ions, which previously caused a corrosive state (like in pitting corrosion), are displaced by a new, protective layer, allowing the material to become ‘passive’ and stable in its environment again.
Repeatability – It is a term which is used to refer to the test-result variability associated with a limited set of specifically defined sources of variability within a single laboratory.
Repeatability (of results of measurements) – It is the closeness of the agreement between the independent results of successive measurements of the same measurand carried out under the same conditions of measurement which is obtained with the same method on identical test material, under the same conditions (same operator, same apparatus, same laboratory and after short intervals of time). These conditions are called repeatability conditions. Repeatability conditions include (i) the same measurement process, (ii) the same observer, (iii) the same measuring instrument, used under the same conditions, (iv) the same location, and (v) repetition over a short period of time. Repeatability can be expressed quantitatively in terms of the dispersion of characteristics of the results. The measure of repeatability is the standard deviation qualified as repeatability standard deviation.
Repeated bending test – It is also known as a cyclic bending test or fatigue bending test. It evaluates a material’s ability to withstand repeated bending forces without failure, simulating real-world conditions where materials are subjected to cyclic loading.
Repeated impact – It is the preferred term when all impacts are superimposed on the same point or zone.
Repeated loading – It is also known as cyclic or repetitive loading, It refers to the continuous and repeated application of a load (stress, strain, and force etc.) to a material or structural component, potentially leading to fatigue and eventual failure.
Repeated measurements – These refer to the process of taking multiple sets of measurements at specific test points during an experiment, which helps in estimating the variances of measurement errors and assessing the fit of the estimates.
Repeated stress – It refers to a type of stress which varies from zero to a maximum value of the same nature (tension or compression), or a stress which changes over time in a repeated fashion. In case of human resource, repeated stress refers to ongoing or chronic exposure to environmental or psychological factors which cause physical or emotional strain. It can result from long-term job demands, relationship difficulties, financial pressures, or other life challenges.
Repeated tension test – It is also known as a cyclic tensile test. It is a mechanical test where a material sample is subjected to repeated cycles of tensile (pulling) stress until failure, allowing engineers to assess its fatigue strength and durability.
Repeaters and looping channels – Repeaters are devices used to receive the work piece as it emerges out from one stand and loop it through 180-degree into an adjacent stand automatically. This consists of grooved channels or troughs which guide the leading end of the rolling stock through 180 degree or in some cases through an S-shaped path in forward running repeaters. The front end of the stock is driven round the repeater by the succeeding stock until it is gripped by the next stand. The speed matching between the adjacent stands is normally such that the succeeding stand runs slightly slower than the balancing speed which causes the loop to grow in size. The repeating channels are designed to allow the stock to kick out on to a flat table under these conditions. Sometimes the repeaters function as twist guides as well.
Repeating coil – It is an old name for a transformer, which is especially used in telephone circuits.
Replacement ore – It is the ore formed by a process during which certain minerals have passed into solution and have been carried away, while valuable minerals from the solution have been deposited in the place of those removed.
Replacement part – It is a component designed to substitute a damaged, worn, or broken original part of a machine or equipment, ensuring its continued operation or functionality. These parts are to be interchangeable and fit as per the same specifications, allowing for easy repair without custom fitting and minimizing maintenance downtime. Replacement parts can come from the original equipment manufacturer (OEM), a third-party aftermarket supplier, or be refurbished.
Replica – It is a reproduction of a surface in a material. It is normally accomplished by depositing a thin film of suitable material, such as a plastic, onto the sample surface. This film is subsequently extracted and examined by optical microscopy, scanning electron microscopy, or transmission electron microscopy, the latter being the most common. Replication techniques can be classified as either surface replication or extraction replication. Surface replicas provide an image of the surface topography of a sample, while extraction replicas lift particles from the sample.
Replicability – It means getting consistent results across studies aimed at answering the same scientific question, each of which has obtained its own data. Two studies can be considered to have replicated if they get consistent results given the level of uncertainty inherent in the system under study.
Replicast process – It is a ceramic shell process similar to the investment casting process. It uses a pattern made from expanded polystyrene (EPS) and is surrounded by a thin ceramic shell. It is a casting process which utilizes dimensionally precise replicas, typically made from expanded polystyrene, to create moulds for casting, resulting in high-quality, complex castings with minimal finishing needs.
Replicate – In electron microscopy, it means to reproduce using a replica.
Replenishment – It is the process of restoring or maintaining adequate inventory levels by moving goods from a reserve or upstream location to a downstream location, like a production line. It involves monitoring stock levels, forecasting demand, and triggering transactions (such as purchase orders or internal stock transfers) to ensure an item’s availability, hence preventing shortages and supporting efficient supply chain operations.
Report – It is a document or a statement which presents information in an organized format for a specific audience and purpose. Reports are normally given in the form of written documents. Typically reports relay information which have been found or observed. The credible report improves the previous beliefs while dishonest information can question the agency preparing the report.
Reporting – It is the process of systematically collecting, analyzing, and communicating data and information to relevant stakeholders to inform decision-making, track performance, and ensure accountability. This involves defining reporting structures, which establish the formal chain of command and flow of communication, clarifying who is responsible for providing information to whom. Reporting can range from internal operational reports to external financial and sustainability reports, providing a holistic view of the organization’s activities and impact.
Reporting system – It is an organized framework of tools, processes, and people designed to collect, analyze, and present data and information in a structured format, frequently for decision-making, problem-solving, or performance tracking. It involves gathering data from different sources, transforming it into comprehensible reports (like tables, charts, and graphs), and distributing these reports to specific audiences to communicate insights, monitor processes, and facilitate informed actions.
Repository – It consists of long-term radioactive waste storage facility.
Repowering – It means refurbishing the equipment of a power plant, with a view to improved efficiency or life span.
Representative sample – It is a small portion of a larger material, product, or process which accurately reflects the characteristics of the entire batch. The goal is to allow the quality control personnel to make reliable inferences about the quality or properties of the whole, based on the analysis of the smaller, more manageable sample, saving time and resources compared to testing the entire batch.
Representative volume element (RVE) – It is the smallest volume of a heterogeneous material which, when averaged, provides a statistically representative description of the material’s overall properties and behaviour.
Repressing – It is the application of pressure to a previously pressed and sintered powder metallurgy compact, normally for the purpose of improving some physical or mechanical property or for dimensional accuracy.
Reprocessing – It refers normally to the processes used to separate spent nuclear reactor fuel into nuclear materials which can be recycled for use in new fuel and material which is to be discarded as waste.
Reproducibility – It is a term which is used to describe test-result variability with specifically defined components of variance obtained both from within a single laboratory and between laboratories.
Reproducibility (of results of measurements) – It is the closeness of the agreement between the independent results of measurements of the same measurand carried out on identical test material but under different conditions (different operators, different apparatus, different laboratories, and / or after different intervals of time). However, it is to be noted that a valid statement of reproducibility requires specification of the conditions changed. The changed conditions include (i) principle of measurement, (ii) method of measurement, (iii) observer, (iv) measuring instrument, (v) reference standard, (vi) location, (vii) condition of use, and (viii) time. Reproducibility can be expressed quantitatively in terms of the dispersion characteristics of the results. The measure of reproducibility is the standard deviation qualified as reproducibility standard deviation. Reproducibility is closely related to replicability and repeatability. It is a major principle underpinning the scientific method. For the findings of a study to be reproducible means that results obtained by an experiment or an observational study or in a statistical analysis of a data set are to be achieved again with a high degree of reliability when the study is replicated. There are different kinds of replication but typically replication studies involve different researchers using the same methodology. Only after one or several such successful replications should a result be recognized as scientific knowledge.
Repulsion motor – It is a wound rotor induction motor using a pair of short-circuited brushes on a commutator.
Repulsive electrostatic force – It is the push experienced between two or more objects with the same type of electric charge (like two positive charges or two negative charges), causing them to move away from each other. This fundamental force is also known as Coulomb force and follows Coulomb’s law, which describes the strength and direction of the interaction based on the magnitude of the charges and the distance between them.
Request for bid (RFB) – It is a formal document issued by an organization, frequently a government agency, to invite suppliers to submit sealed bids for standardized goods, services, or construction projects. It clearly defines the precise specifications and requirements for what is needed, and the contract is typically awarded to the bidder who submits the lowest price while still meeting all the stated requirements.
Request for proposal (RFP) – It is a formal document an organization issues to solicit detailed solutions and pricing from potential suppliers for a specific project or service. It outlines the project’s requirements, scope, and objectives, allowing suppliers to present their capabilities and how they can meet the need. RFPs are used to foster competition, ensure transparency, and facilitate a data-based vendor selection process for complex procurements.
Request for quotation (RFQ) – It is a process wherein an organization asks a set of potential suppliers or service providers to submit their quotations and stand a chance to supply or provide goods or services. Once the organization receives the quotations, it can choose the vendor which best matches its criteria for the goods or services.
Request for tender (RFT) – It is a formal document issued by a buyer to invite potential suppliers to submit competitive bids for the supply of goods, services, or works. It provides clear details on the project’s scope, establishes the rules of the bidding process, and defines the criteria for evaluating proposals, aiming to ensure transparency, promote competition, and facilitate informed purchasing decisions.
Requirements list – In engineering design, it is a detailed list of the functional requirements with qualitative or quantitative goals and limits for each.
Rerolling quality – It means the quality of the rolled billets from which the surface defects have not been removed or completely removed.
Reroll stock – It is a semi-finished rolled product of rectangular cross-section in coiled form suitable for further rolling. Examples are foil stock and sheet stock.
Research – It is defined as the creation of new knowledge and/or the use of existing knowledge in a new and creative way so as to generate new concepts, methodologies and understandings. This could include synthesis and analysis of previous research to the extent that it leads to new and creative outcomes.
Research and development (R&D) – It is defined as activities designed to advance and sustain the capabilities of the organization in pursuit of its mission. The R&D plan of the organization supports strategic planning by identifying and communicating the set of R&D needs which are reliant on external support. It is intended to help stakeholders understand the context for specialized needs and how they relate to the bigger picture of strengthening the effectiveness and improving the efficiency of organization. Research is planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge is going to be useful in developing a new product or service or a new process or technique or in bringing about a significant improvement to an existing product or process. Development is the translation of research findings or other knowledge into a plan or design for a new product or process or for a considerable improvement to an existing product or process whether intended for sale or use. It includes the conceptual formulation, design, and testing of product alternatives, construction of prototypes, and operation of pilot plants.
Researcher development skill framework (RDSF) – It is made up of five components consisting of a centre and four quadrants, which together cover both the discipline specific and generic skills needed by researchers. centre represents researcher and research. It places the researchers and their research at the centre. The core skills namely (i) subject knowledge (ii) discipline specific skills, and (iii) intellectual ability are unique to the researchers and their research area. In addition to the centre piece, the researcher development skill framework has four quadrants. Within each quadrant there are three skills categories which are then broken down into skills areas with examples. To help develop these skills, training, workshops, and resources are needed. Quadrant 1 represents personal and professional development. It includes (i) self-management, (ii) career management, and leadership and interpersonal skills. Quadrant 2 represents research management. It includes (i) research planning and income management, (ii) data management, digital literacy, and administration, and (iii) research conduct, integrity and ethics. Quadrant 3 represents communication. It includes (i) academic literacy and writing, (ii) verbal and visual presentation skills, and (iii) publication and dissemination. Quadrant 4 represents engagement and impact. It includes (i) outreach and influence, (ii) knowledge exchange and innovation, and (iii) education.
Research management – It includes (i) research planning and income management, (ii) data management, digital literacy and administration, and (ii) research conduct, integrity and ethics. The skill areas for research planning and income management include (i) research project development, (ii) grant seeking (pre-award), and (iii) grant management (post award).
Research plan – It is a framework which shows how a researcher intends to approach the research topic. The plan can take several forms such as a written outline, a narrative, a visual / concept map or timeline. It is a document which changes and develops as researchers conduct their research. Components of a research plan include (i) research conceptualization which introduces the research question, (ii) research methodology which describes the approach to the research question, (iii) literature review, critical evaluation and synthesis, which consists of systematic approach to locating, reviewing and evaluating the work (text, exhibitions, and critiques etc.) relating to the research topic, and (iv) communication which is geared toward an intended audience, shows evidence of researcher’s inquiry.
Restricted Resources / Reserve – Restricted Resources / Reserve is that part of any resource / reserve category which is restricted from extraction by laws or regulations. For example, restricted reserves meet all the requirements of reserves except that they are restricted from extraction by laws or regulations.
Reserves – Reserves are that part of the reserve base which can be economically extracted or produced at the time of determination. The term reserves need not signify that extraction facilities are in place and operative. Reserves include only recoverable materials. Hence, terms such as ‘extractable reserves’ and ‘recoverable reserves’ are redundant and are not a part of the classification system.
Reserve base – Reserve base is that part of an identified resource which meets specified minimum physical and chemical criteria related to current mining and production practices, including those for grade, quality, thickness, and depth. The reserve base is the in-place demonstrated (measured plus indicated) resource from which reserves are estimated. It can encompass those parts of the resources which have a reasonable potential for becoming economically available within planning horizons beyond those that assume proven technology and current economics. The reserve base includes those resources which are currently economic (reserves), marginally economic (marginal reserves), and some of those that are currently subeconomic (subeconomic resources). The term Geological reserve has been applied by others normally to the reserve-base category, but it also can include the inferred-reserve base category.
Reserves estimate – It is the calculated, quantifiable quantity of a resource, such as oil, gas, or minerals, which can be extracted economically and technically from the earth, based on geological, engineering, and economic data. These estimates are crucial to make operational and investment decisions, determine financial status, and comply with regulations, though the estimates themselves can vary based on methodology and are distinct from production levels.
Reserves-to-production ratio (R/P ratio) – It is an indicator which estimates how many years a non-renewable resource, like oil or natural gas, is going to last at its current rate of consumption. It is calculated by dividing the known quantity of economically recoverable reserves by the quantity of the resource produced in one year. This ratio helps to forecast resource availability and plan for future supply needs, although it is an estimate which does not account for new discoveries or changes in production and consumption patterns.
Reservoir – It is a man-made lake which collects and stores water for future use. Reservoir for hydraulic fluid is a tank for holding the fluid required to supply the system, including a reserve to cover any losses from minor leakage and evaporation. The reservoir is generally designed to provide space for fluid expansion, permit air entrained in the fluid to escape, and to help cool the fluid. The reservoir tank is either vented to the atmosphere or closed to the atmosphere and pressurized. Hydraulic oil flows from the reservoir tank to the pump, where it is forced through the system and eventually returned to the reservoir tank. The reservoir tank not only supplies the operating needs of the system, but it also replenishes fluid lost through leakage. Furthermore, the reservoir serves as an overflow basin for excess fluid forced out of the system by thermal expansion (the increase of fluid volume caused by temperature changes), the accumulators, and by piston and rod displacement. The reservoir also furnishes a place for the fluid to purge itself of air bubbles which can enter the system. Foreign matter picked up in the system can also be separated from the hydraulic fluid in the reservoir or as it flows through line filters. Reservoir tank is either pressurized or non-pressurized.
Reservoir area – It is the total surface of a reservoir measured in a horizontal plane at an elevation corresponding to the full supply level of the reservoir.
Reservoir capacity – It is the total volume of water a reservoir is capable of holding when filled up to the full supply or normal water level.
Reservoir equipment – It refers to the components and tools used in and around a reservoir, primarily for hydraulic systems, which include air breathers, gauges, filters, and suction strainers, to manage fluid levels, prevent contamination, and ensure proper system function.
Reset – It means the realigning or adjusting of dies or tools during a production run. It is not to be confused with the operation setup which occurs before a production run.
Resettable fuse – It is a circuit protective device which opens on excess current, and then, on cooling off, restores the circuit automatically.
Residue – It is the small amount of substance or material that remains after a main part has been removed or a process has been completed. The process of leaving a residue involves actions like evaporation, combustion, filtration, or the extraction of something else, leaving the leftover material behind.
Residual – It can refer to either residual elements or residual stresses. Residual elements are unwanted impurities or minor alloying elements present in a metal after refining which can substantially affect its properties, while residual stresses are locked-in internal stresses within a material, even in the absence of external forces, frequently resulting from plastic deformation or non-uniform heating / cooling.
Residual austenite – It is also known as retained austenite. It is the austenitic phase in steel which remains untransformed into martensite after a quenching heat treatment process. It exists at room temperature alongside the hard martensitic phase. The amount of residual austenite depends on the steel’s chemical composition, particularly its carbon content and alloying elements. While it can provide benefits like increased work hardening in some applications, it also lowers hardness and can contribute to fatigue failure, necessitating careful control in heat-treated components.
Residual current circuit breaker – It is a device which detect differences in current between live and neutral conductors through a transformer, triggering a relay to break the circuit if a leakage occurs, thereby preventing potential electric shocks. It is a circuit breaker which detects unbalance of phase currents because of the ground fault.
Residual dissolved oxygen – It refers to the quantity of oxygen that remains dissolved in a liquid, such as water, after a process designed to remove or reduce it, like purging or deaeration. When a liquid is treated to remove dissolved oxygen (e.g., through deaeration in boilers or water treatment), the remaining oxygen which cannot be removed is considered residual dissolved oxygen.
Residual elements – These are defined as elements which are not added on purpose to steel and which cannot be removed by simple metallurgical processes. These are small quantities of elements unintentionally present in an alloy. Examples of residual elements are copper, nickel, arsenic, lead, tin, antimony, molybdenum, and chromium etc. The presence of residual elements in steel can have strong effects on mechanical properties. There is hence clearly the need to identify and to quantify the effects of residual elements in order to keep these effects within acceptable limits. Residual elements, or at least some of them, have an influence on processing conditions and regimes, from casting to the final annealing, and possibly on all mechanical properties.
Residual fuels – These are the products remaining from crude petroleum by removal of some of the water and an appreciable percentage of the more volatile hydro-carbons.
Residual gas analysis – It is a technique which is used to identify and quantify the different gas species present in a vacuum environment, helping to understand vacuum purity, identify leaks, and monitor contamination.
Residual gas analyzer (RGA) – It is a small and normally rugged mass spectrometer, typically designed for process control and contamination monitoring in vacuum systems. When constructed as a quadrupole mass spectrometer, there exist two implementations, utilizing either an open ion source (OIS) or a closed ion source (CIS). Residual gas analyzers can be found in high vacuum applications such as research chambers, surface science setups, accelerators, and scanning microscopes etc. These analyzers are used in majority of the cases to monitor the quality of the vacuum and easily detect minute traces of impurities in the low-pressure gas environment.
Residual impacts – It consists of the impacts of climate change which occur after adaptation.
Residual life – It refers to the remaining useful lifespan of an object, or component representing the time left before the end of its expected service, considering its current condition. It is an estimation of future function, frequently determined through ‘residual life assessment’ (RLA) studies.
Residual ores – These ores are normally products of the surficial weathering of rocks but can include ores formed by hydrothermal oxidation and leaching. Ores of this type were formed extensively in Precambrian iron formations by leaching of silica, which commonly constituted in excess of 50 % of the rock. Oxidation changed iron carbonate, silicate minerals, and magnetite to hematite or limonite.
Residual porosity – It also known as closed porosity or isolated porosity. It refers to the volume of pore spaces within a material which are disconnected from the rest of the pore system or the external environment. Unlike open pores, residual pores do not allow for the passage of fluids or gases and hence do not contribute to phenomena like mass transfer, permeability, or adsorption. However, residual porosity still influences a material’s mechanical properties.
Residual resistance ratio – It is a metric used to assess the purity and quality of a material, defined as the ratio of its electrical resistance at room temperature (typically 273 K or 293 K) to its resistance at a very low temperature, frequently around 4.2 K (the boiling point of helium).
Residual-resistivity ratio – It is also known as residual-resistance ratio or just is normally defined as the ratio of the resistivity of a material at room temperature and at 0 K. Of course, 0 K can never be reached in practice so some estimation is usually made. Since the residual-resistance ratio can vary quite strongly for a single material depending on the quantity of impurities and other crystallographic defects, it serves as a rough index of the purity and overall quality of a sample. Since resistivity normally increases as defect prevalence increases, a large residual-resistance ratio is associated with a pure sample. residual-resistance ratio is also important for characterizing certain unusual low temperature states such as the Kondo effect and super-conductivity. Since it is a unitless ratio there is no difference between a residual resistivity and residual-resistance ratio.
Residual risk – It is the risk which remains in unmanaged form, even when disaster risk reduction measures are in place and for which emergency response and recovery capacities are to be maintained. The presence of residual risk implies a continuing need to develop and support effective capacities for
emergency services, preparedness, response and recovery together with socio-economic policies such as safety nets and risk transfer mechanisms.
Residuals – It refer to ‘tramp elements’ such as copper (Cu) and tin (Sn), which are typically introduced into the steelmaking process in the form of unsorted or contaminated scrap and which can impair the physical and mechanical properties of steel.
Residual shrinkage – It is the continued reduction in size or the remaining potential for size reduction in a material after initial shrinkage has occurred, frequently because of the internal stresses. It can happen during manufacturing and is related to a material’s latent tendency to shrink over time, even after processing attempts to stabilize its dimensions.
Residual strain – It is the strain which is associated with residual stress.
Residual strength – It is the load or force (normally mechanical) which a damaged object or material can still carry without failing. It is the strength which a material can still withstand, even with cracks or other defects present. Material toughness, fracture size and geometry as well as its orientation all contribute to residual strength.
Residual stress – It is the stress existing in a body at rest, in equilibrium, at uniform temperature, and not subjected to external forces. It is frequently caused by the forming or thermal processing curing process. It is an internal stress not depending on external forces resulting from such factors as cold working, phase changes, or temperature gradients. It is stress present in a body which that is free of external forces or thermal gradients. It is the stress remaining in a structure or member as a result of thermal or mechanical treatment or both. Stress arises in fusion welding mainly since the weld metal contracts on cooling from the solidus to room temperature.
Residual-stress relaxation mechanism – It is a process by which internal stresses within a material, which exist independently of external loads, are reduced or eliminated, frequently through plastic deformation, thermal annealing, or repeated loading cycles. The specific mechanism depends on the material and the method used, but the common outcome is the lessening of stress through inelastic behavior, restoring the material closer to its elastic limit.
Residual stress sensitivity factor – It quantifies how much a material’s fatigue strength is reduced because of the presence of residual stresses and geometric stress concentrations (like notches).
Residual tensile strength – It is the remaining tensile strength a material possesses after experiencing damage or exposure to extreme conditions. It quantifies the material’s ability to resist pulling forces even when degraded by such common factors as high temperature because of fire, internal damage, or mechanical impact.
Residue – These are contaminants (oil, grease, dirt, rust and mill scale) which unless removed, prevents complete galvanizing of the steel surface.
Resilience – It is the quantity of energy per unit volume released on unloading. It is the capacity of a material, by virtue of high yield strength and low elastic modulus, to show considerable elastic recovery on release of load. Resilience is also the ability of ceramic fibres to spring back after compression to 50 % of thickness. Resilience is the ratio of the thickness of a product after the application and relaxation of a compressive force which reduces the original thickness to 50 % of its original value, to its original thickness.
Resilient seat – It is a valve seat containing a soft seal, such as an O-ring, to ensure tight shut-off.
Resin – It is a solid or highly viscous liquid that can be converted into a polymer. Resins can be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, predominantly terpenes. It is a bead-like material used in chemical exchange for softeners and de-alkalizers.
Resin binder – It is a substance, frequently a polymer, which acts as a glue to hold other materials together, forming a cohesive unit with structural integrity and improved mechanical properties. Its main role is to bind solid particles or fibres, creating a film, improving adhesion, and imparting characteristics like hardness and flexibility to the final product, from coatings and abrasives to composites and electrodes.
Resin binder process – It involves creating and applying a resin-based substance to join components, forming a coherent structure by blending monomers / additives, conducting a polymerization reaction to form the resin, and then using this cured resin as an adhesive or film-forming material to bond other materials or consolidate powders. The specific steps and conditions, such as temperature and catalysts, vary depending on the type of resin and its intended application, whether it is a coating, or a foundry sand binder.
Resin bonded – It describes a method of attaching one material to another using a composite resin or adhesive, creating a bond that is typically strong yet minimally invasive. This term has several specific applications such as a resin bond in a grinding wheel, which uses a metal-clad diamond grit for self-sharpening; and in construction, and resin-bonded aggregates which use a layer of resin to adhere aggregate stones, creating a solid, non-porous surface.
Resin bonding – It is the use of resin to produce a bond in a refractory when heated to a relatively low temperature (up to 800 deg C).
Resin-coated sand – It is sand, frequently quartz or ceramic, with a thin layer of thermo-setting resin bonded to its surface, mainly used in foundry operations for creating strong and precise moulds and cores for casting metal. The resin coating, applied through different heating and mixing processes, provides improved strength, flowability, and a superior surface finish for the final casting, enabling the production of high-precision castings.
Resin composite – It is a material formed by combining a polymer resin (matrix) with reinforcing components (like fibres or particles) to create a new material with properties superior to its individual constituents. These materials leverage the binding and load-transferring ability of the resin with the strength, stiffness, or other enhanced characteristics of the reinforcement.
Resin content – It is the quantity of resin in a laminate expressed as either a percentage of total weight or total volume.
Resin film infusion (RFI) – It is a variant of the resin transfer moulding process in which a layer of solid resin film is placed along with a dry preform in a matched.
Resin impregnation – It is a process where a resin, frequently a polymer, is introduced into a porous material, typically under vacuum, pressure, or both, to ensure the resin penetrates and fills voids, improving structural integrity and other properties upon curing.
Resin matrix – It is the continuous, binding polymeric phase in a composite material which holds reinforcement materials, such as fibres or fillers, together. It forms the structural backbone, providing overall shape and cohesion to the composite while distributing stress and protecting the reinforcing elements from damage. Common resin matrices include epoxy, polyester, and vinyl ester resins, which can be reinforced with materials like carbon fibre, glass fibre, or silica particles.
Resin matrix composites – These are materials where a matrix of organic resin (like epoxy or polyester) surrounds and binds together reinforcing fibres or particles, resulting in a composite with improved properties compared to the individual components.
Resinoid – It consists of a class of thermosetting synthetic resins, either in their initial temporarily fusible state or in their final infusible state.
Resinoid wheel – It is a grinding wheel bonded with a synthetic resin.
Resin pocket – It is an apparent accumulation of excess resin in a small, localized section visible on cut edges of moulded surfaces, or internal to the structure and non-visible.
Resin-rich area – It is the localized area filled with resin and lacking reinforcing material.
Resin-starved area – It is the localized area of insufficient resin. It is normally identified by low gloss, dry spots, or fibre showing on the surface.
Resin system – It is a mixture of resin and ingredients such as catalyst, initiator, diluents, and so on, needed for the intended processing and final product.
Resintering – It is the application of pressure to a sintered compact, normally for the purpose of improving a physical or a mechanical property or for dimensional accuracy.
Resin transfer moulding (RTM) – It is a closed-mould process which is used to produce composite parts by injecting resin into a mould containing preformed, dry fibre reinforcements, which then cures, resulting in a strong, durable component.
Resin transfer moulding (RTM) process – It is a closed-mould process for manufacturing fibre-plastic composite parts, where a dry fibre preform is placed in a mould, and then liquid resin is injected under pressure to saturate the fibres. The resin cures within the mould to form a strong, stiff component, making this process ideal for producing complex, high-performance composite parts.
Resist – It is the coating material which is used to mask or protect selected areas of a substrate from the action of an etchant, solder, or plating. It is a material which is applied to prevent flow of brazing filler metal into unwanted areas.
Resistance – It is the act of opposing or withstanding something, or the power to do so. It is a force which acts to stop the progress of something or make it slower. It is also the impediment to gas flow, such as pressure drop or draft loss through a dust collector. It is normally measured in millimeter water column.
Resistance brazing – It is a brazing process in which the heat needed is obtained from the resistance to electric current flow in a circuit of which the work-piece is a part. It is a resistance joining process. The work-pieces are heated locally, and the filler metal which is preplaced between the work-pieces is melted by the heat generated from resistance to the flow of electric current through the electrodes and the work. In the usual application of resistance brazing, the heating current is passed through the joint itself. Equipment is the same as that used for resistance welding, and the pressure needed for establishing electrical contact across the joint is ordinarily applied through the electrodes. The electrode pressure is also the normal means for providing the tight fit needed for capillary behavior in the joint. The heat for resistance brazing can be generated mainly in the workpieces themselves, in the electrodes, or in both, depending on the electrical resistivity and dimensions.
Resistance butt welding – It is used to join components of similar cross section by making a weld across the entire section in a single operation. Heat is produced in the weld region by resistance to the passage of the welding current through the parts, which are held under a preset end force. As the material heats, the force forges the soft material to consolidate and complete the joint. Resistance butt welding is hence a solid-state process. The force across the interface causes deformation which brings the surfaces into sufficiently close contact to make a weld, and there is some expulsion of material which carries oxide film and contaminants out of the joint. Applications include wire and rod joints up to about 16 millimeters diameter, including chain, and narrow strip joints such as automobile road wheel rims.
Resistance, electrical – It is a measure of its opposition to the flow of electric current. Electrical resistance shares some conceptual parallels with mechanical friction. The unit of electrical resistance is the ohm. The resistance of an object depends in large part on the material it is made of. Objects made of electrical insulators like rubber tend to have very high resistance, while objects made of electrical conductors like metals tend to have very low resistance.
Resistance element – It is a component designed to oppose the flow of electric current, heat, or other forces, with its resistance varying in response to external stimuli like strain or temperature, or to dissipate energy as heat in electrical circuits. As an example, a strain gauge uses a resistive element made of conductive rubber or metallic alloys to measure deformation in a material by detecting changes in its resistance. In other contexts, a resistance element can refer to the resistive part of a resistor, which generates heat when current passes through it, a function used in devices like toasters or for flammability testing.
Resistance, flow – It is the reciprocal of conductance.
Resistance furnaces – In these furnaces, heat transfer occurs either directly or indirectly as per Ohm’s and Joule’s laws. They can be operated in an alternating current or direct current mode. Furnaces which implement direct resistance include (i) resistance furnaces for solid-state reactions (production of graphite and carbides), (ii) resistance furnaces for the production of copper, nickel, iron, tin, and zinc or their intermediate products from oxides and sulphides and slags, (iii) electro slag refining (ESR) for the production of clean ferrous or non-ferrous metals and alloys such as titanium, steels, and super alloys, (iv) furnaces which employ a combination of arc and resistance heating are used for the production of calcium carbide , ferroalloys, liquid iron, phosphorus, and silicon compounds by reduction, (v) fused-salt electrolysis cells for the production of aluminum and alkali metals can also be considered to be electrochemical thermal reactors, and (vi) salt-bath furnaces for the heat treatment of metals.
Resistance fusion welding – It is also known as electric resistance welding (ERW). It is a welding process which joins metals by passing a strong electric current through the metal combination, generating heat through electrical resistance, and applying pressure to fuse the materials together.
Resistance gauge – It is also known as an electrical resistance strain gauge. It is a transducer which measures mechanical strain by detecting the change in its own electrical resistance as it deforms. It consists of a metallic wire or foil grid bonded to a surface, when the surface stretches or compresses, the grid’s length changes and its electrical resistance changes proportionally, allowing for the measurement of stress and structural integrity.
Resistance heating – It is the heating because of the heat generated due to the resistance of the heat conductor. It normally involves the highest electricity costs, and can need circulating fans to assure the temperature uniformity usually achievable by the flow motion of the products of combustion in a fuel-fired furnace. Silicon control rectifiers have made input modulation more economical with resistance heating. Various materials are used for electric furnace resistors. The common material which is used is nickel-chromium alloy, in the form of rolled strip or wire, or of cast zigzag grids (mostly for convection). Other resistor materials are molten glass, granular carbon, solid carbon, graphite, or silicon carbide. It is occasionally possible to use the load that is being heated as a resistor.
Resistance seam welding – It is a resistance welding process which produces coalescence at the faying surfaces of overlapped parts progressively along a length of a joint. The weld can be made with over-lapping weld nuggets, a continuous weld nugget, or by forging the joint as it is heated to the welding temperature by resistance to the flow of the welding current.
Resistance sintering under pressure – It is a hot-pressing technique where a powder compact is simultaneously heated by passing a low voltage, high amperage current through it while applying pressure, leading to densification and consolidation of the material.
Resistance soldering – It is a soldering process in which the heat needed to melt the solder is developed by the resistance of the material when a large electrical current is supplied. Resistance soldering can be applied to electrically conductive materials which allow the passage of electric current. The process can be used for selective spot soldering of conductive materials which allow the passage of electric current. The process can be used for selective spot soldering of small components, for the soldering of closely placed parts on an assembly, or for heat restriction when necessary. It is similar in several ways to resistance brazing. When the current is applied, rapid local heating occurs, melting the solder. This molten solder wets the surface. As a result, the resistance in the material falls and the current increases, tripping a control. The heat rapidly dissipates into the surrounding area, and the solder quickly solidifies. The resistance soldering process can be used in all soldering operations and with all solderable metals. The only limitations are the thickness and the design of the parts to be soldered. Resistance soldering is used to join steels (e.g., carbon, low alloy, and stainless) and non-ferrous alloys (e.g., aluminum and aluminum alloys, nickel and nickel alloys, and copper and copper alloys) up to 3.2 millimeters in thickness.
Resistance spot welding – It is a resistance welding process which produces coalescence at the faying surfaces of a joint by the heat obtained from resistance to the flow of welding current through the work-pieces from electrodes that serve to concentrate the welding current and pressure at the weld areas.
Resistance temperature detector (RTD) – It is a device which measures temperature through the resistance of a conductor. Resistance of the conductor can vary with time. It is this property of the conductor that is used for industrial temperature measurement. The primary purpose of the resistance temperature detectors is to produce a resistance alteration in response to temperature. Metals normally show high temperature coefficients, indicating resistance increases as temperature rises. On the other hand, carbon and germanium typically demonstrate low temperature coefficients, hence showing a resistance decrease with increasing temperature.
Resistance thermometer – It is an instrument for measuring electrical resistance which is calibrated in units of temperature instead. Resistance thermometers are made of a pure metal, such as platinum, nickel, or copper. The electrical resistance of such a material is almost linearly dependent on temperature. Resistance thermometers are stable, having a small drift.
Resistance to slag, glass melts, gasses, and vapours – The slag resistance characterize the resistance of refractories to chemical attack of any type, including that of glass and vapours. The destructive agents coming into contact with refractories are of different composition and the destruction processes are correspondingly many. The method of determination of slag resistance is described in various standards. Refractory brick destructions are not only caused by liquid slags and glass melts but gasses and vapours also influence the service life of the refractory bricks due to several individual reasons.
Resistance voltage – It is the voltage across a resistive element (like a resistor) in a circuit. It also refer to the voltage generated by resistance, such as in a heating element where the resistance of a material opposes the current, converting electrical energy into heat and hence creating a voltage.
Resistance welding – It consists of a group of welding processes which produce coalescence of metals with resistance heating and pressure.
Resistance welding electrode – It is the part(s) of a resistance welding machine through which the welding current and, in majority of the cases, force is applied directly to the work. The electrode can be in the form of a rotating wheel, rotating bar, cylinder, plate, clamp, chuck, or modification thereof.
Resistance welding gun – It is a manipulatable device to transfer current and provide electrode force to the weld area (normally in reference to a portable gun).
Resistance welding machine – It is an equipment which utilizes the Joule heating effect to join metal work-pieces by passing a high electrical current through them and applying mechanical pressure. The machine contains electrodes, a transformer, and mechanisms for current control and pressure application, which collectively produce sufficient heat at the interface to melt and fuse the metals without the use of filler material.
Resistive circuit – It is a circuit containing resistive elements only, and no capacitors or inductors.
Resistive element – It is the core component of a resistor, typically made from a material with high electrical resistivity, designed to oppose the flow of electric current and convert electrical energy into heat. Its main function is to limit or control current in a circuit, with its specific resistance value (measured in ohms) determining the relationship between voltage and current as per Ohm’s law (V=IR). The resistive element is made from materials like carbon, metal alloys (e.g., nichrome), or semi-conductors, chosen for their ability to impede current flow.
Resistive force – It is also called friction. It is the force which is the resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Types of resistive force include dry, fluid, lubricated, skin, and internal and several others. The study of the processes involved is called tribology.
Resistive load – It is an electrical component or device which converts electrical energy into thermal energy, or heat, and impedes the flow of current. For such loads, the current and voltage waveforms are in phase, meaning they reach their peak and zero values at the same time, resulting in a power factor of unity (1).
Resistive pressure measurement – The principle of resistive pressure measurement is based on the measurement of the change in resistance of electric conductors caused by a pressure-dependent deflection. The equation applied for the resistance of an electric conductor is R = r. (l/a) where ‘R’ is electrical resistance, ‘r’ is resistivity, ‘l’ is length, and ‘a’ is the cross-sectional area. If a tensile force is applied to the conductor, its length increases and its cross-sectional area decrease. The resistivity of a metallic conductor is a (temperature-dependent) constant for a particular material and, hence, independent of the geometry, so the electrical resistance increases as a result of the elongation. In the case of compression, the opposite applies. The principle of resistive pressure measurement is achieved using a main body which shows a controlled deflection under pressure. This main body frequently has a ‘thin’ area referred to as the diaphragm, which is weakened intentionally. The degree of deflection caused by the pressure is measured using metallic strain gauges.
Resistivity – It is the property of a material which impedes current flow. It is the ability of a material to resist passage of electrical current either through its bulk or on a surface.
Resistivity index (I) – It is a dimensionless ratio which quantifies the change in a rock’s electrical resistivity when its pore spaces are partially filled with conductive fluids like water compared to when they are completely filled with water. It is calculated as the true resistivity (Rt) of the partially saturated rock divided by the resistivity of the completely water-saturated rock (Ro) or I = Rt/Ro. The presence of non-conductive fluids such as oil or gas increases the rock’s resistivity, leading to a resistivity index higher than 1.
Resistivity survey – It is a geophysical technique which is used to measure the resistance of a rock formation to an electric current.
Resistivity tools – These are specialized devices designed to measure electrical resistivity in geological formations, with the capability to detect invasion and determine fluid types in the shallow reading porosity zones, typically penetrating only a few centimeters into the formation.
Resistor – It is a circuit component which primarily has resistance. It is a passive two-terminal electrical component which implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses. High-power resistors which can dissipate several watts of electrical power as heat can be used as part of motor controls, in power distribution systems, or as test loads for generators. Fixed resistors have resistances which only change slightly with temperature, time, or operating voltage. Variable resistors can be used to adjust circuit elements (such as a volume control or a lamp dimmer), or as sensing devices for heat, light, humidity, force, or chemical activity. Resistors are common elements of electrical networks and electronic circuits. Practical resistors as discrete components can be composed of different compounds and forms. Resistors are also implemented within integrated circuits.
Resite – It is also called C-stage. It is the final stage in the reaction of certain thermosetting resins in which the material is practically insoluble and infusible. The resin is in a fully cured thermoset moulding is in this stage.
Resitol – It is also called B-stage. It is an intermediate stage in the reaction of certain thermosetting resins in which the material softens when heated and is plastic and fusible but does not entirely dissolve or fuse. The resin is in an uncured prepreg or premix is normally in this stage.
Resole – It is also called A-stage. It is an early stage in the preparation of certain thermosetting resins in which the material is still soluble in certain liquids, and can be liquid or capable of becoming liquid upon heating.
Resolidified material – It refers to the substance which reverts to a solid state after being melted during a laser cutting process. Its amount can be reduced through optimized laser parameters, leading to improved cutting-edge quality.
Resolution – It is the capacity of an optical or radiation system to separate closely spaced forms or entities, in addition, the degree to which such forms or entities can be discriminated. Resolution is normally specified as the minimum distance by which two lines or points in the object are to be separated before they can be revealed as separate lines or points in the image.
Resolution bandwidth (RBW) – It is the bandwidth of the intermediate frequency (IF) filter in a spectrum analyzer, defining the smallest frequency difference between two signals which the instrument can separately identify. A narrow resolution bandwidth provides superior frequency resolution, allowing for distinct visualization of closely spaced signals, while a wider resolution bandwidth improves sweep speed and reduces the noise floor but can merge close signals into a single trace.
Resolution lithography – It is a technique used in semi-conductor manufacturing to achieve higher resolution in the patterning of micro-electronic devices, utilizing advanced methods such as electron beam and X-ray lithography to meet stringent dimensional needs as technology scales down to smaller features.
Resolution tomography – It refers to the use of computerized tomography (CT) to examine features at varying resolutions to balance high-detail imaging with computational feasibility. It involves selecting a specific resolution level during the scan to accurately reconstruct features, such as fibre orientations in materials, without needing overly long scan times or excessively large data sets.
Resolved shear stress (RSS) – It is the shear stress component acting on a specific slip plane in a specific slip direction within a material, calculated from an applied tensile or compressive stress using a geometric factor called the Schmid factor. It is the actual stress which causes dislocations to move and initiate plastic deformation when it reaches a critical threshold, known as the critical resolved shear stress (CRSS).
Resolvent – It is a linear operator (or transfer function) in fluid dynamics, which characterizes the response of a linear system to harmonic forcing inputs, mapping these inputs to their corresponding harmonic outputs with associated energy gains. Resolvent analysis inspects this operator to find the most responsive forcing modes and the most receptive output states, providing a powerful tool for understanding and predicting the dominant instabilities and coherent structures in complex flows, such as turbulence, by identifying the linear mechanisms which amplify perturbations about a base flow.
Resolver – It is a transformer-like rotary transducer which measures rotation as an analog value.
Resolving power – It is the ability of a given lens system to reveal fine detail in an object.
Resonance – It is a phenomenon which occurs when an object or system is subjected to an external force or vibration that matches its resonant frequency, defined as the frequency which generates the maximum amplitude response in the system. In chemistry, resonance is a way of describing bonding in certain molecules or polyatomic ions by the combination of several contributing structures (or forms, also variously known as resonance structures or canonical structures) into a resonance hybrid (or hybrid structure) in valence bond theory. It has particular value for analyzing delocalized electrons where the bonding cannot be expressed by one single Lewis’s structure. The resonance hybrid is the accurate structure for a molecule or ion. It is an average of the theoretical (or hypothetical) contributing structures.
Resonance damping – It refers to mechanisms and design strategies which reduce the amplitude of oscillations in a system when it is subjected to a periodic force at or near its natural frequency, hence preventing potentially destructive large-amplitude vibrations by dissipating the system’s energy. Damping can be achieved through different means, such as fluid viscous damping in shock absorbers or through more complex devices like tuned mass dampers, to ensure structural integrity and operational stability.
Resonance energy – It is the energy difference between a molecule’s actual, delocalized structure and the energy of its most stable hypothetical Lewis-structure, indicating increased stability because of the electron delocalization. Resonance energy is also associated with mechanical resonance or electrical resonance, referring to the energy transferred non-radiatively to a system when it is driven at its natural frequency, leading to amplified vibrations or oscillations.
Resonance frequency – It is a specific frequency at which a system tends to oscillate at its maximum amplitude, allowing even small periodic driving forces to produce large amplitude vibrations because of the system’s ability to store vibrational energy. When damping is minimal, the resonance frequency is approximately equal to the system’s natural frequency.
Resonance wavelength – It refers to the specific wavelength of a wave which causes a system to resonate, leading to a substantial increase in the amplitude of its oscillations. This occurs when the wave’s wavelength (and hence its frequency) matches a natural frequency of the system, setting up a standing wave. The concept is applied in several fields, such as designing micro-cavities for single-mode operation in computer science, optimizing surface-enhanced Raman spectroscopy, and analyzing acoustic resonance in piping systems to avoid destructive vibrations.
Resonant cavity – It is an opening which when excited by an electron stream or other means, oscillates at a particular frequency.
Resonant circuit – It is also known as an LC circuit or tank circuit. It is an electrical circuit containing an inductor (L) and a capacitor (C) which produces a maximum response at a specific frequency, the resonant frequency. At this frequency, the inductive reactance and capacitive reactance of the circuit are equal, causing the circuit to act as a resonator, storing and exchanging energy between the inductor and capacitor. These circuits are fundamental to electronics, used in applications such as wireless communication, tuning, and signal processing.
Resonant energy – It refers to the energy associated with mechanical resonance, where an external force matches the system’s natural frequency, leading to amplified oscillations and stored potential energy. This concept also applies to electromagnetic resonance, such as in RLC (resistor, inductor, and capacitor) circuits, where energy exchange is maximized between the inductor and capacitor at a specific resonant frequency. Another context is Forster resonance energy transfer (FRET), where energy is non-radiatively transferred between molecules over short distances.
Resonant frequency – It is the specific natural frequency at which an oscillating system, such as a mechanical structure or an electrical circuit, vibrates with maximum amplitude when subjected to a periodic external force. At this frequency, the system efficiently absorbs energy, leading to a peak response or a stable performance. For example, in an RLC (resistor, inductor, and capacitor) circuit, it is the frequency where the inductive and capacitive reactances cancel each other out, resulting in maximum current flow in a series circuit.
Resonant inductive coupling – It is a form of energy transfer between two physically close tuned circuits.
Resonant sensor – It is a transducer which measures a physical or chemical parameter by detecting changes in the mechanical resonance frequency of a vibrating element. This change in frequency, which occurs in response to applied forces, stress, or mass, is directly related to the measured quantity. Resonant sensors offer substantial advantages, including high sensitivity, excellent precision, and a digital-like frequency output signal that is less susceptible to noise and analog-to-digital conversion errors compared to traditional analog sensors.
Resource – Resource is a concentration of naturally occurring solid, liquid, or gaseous material in or on the earth’s crust in such form and amount that economic extraction of a commodity from the concentration is currently or potentially feasible. It is the calculated quantity of material in a mineral deposit, based on limited drill information.
Resource allocation – It is the process of assigning and distributing available resources, such as time, personnel, equipment, materials, and budget, to different tasks and projects in an optimal way to achieve specific goals efficiently and effectively. The goal is to maximize productivity, meet project deadlines and budget constraints, and maintain quality by ensuring the right resources are available at the right time for all necessary activities.
Resource classification – Resources are also classified as productive resources (which are needed for achieving goals) and administrative resources (which govern the use of productive resources). The growth of the organization is limited by the bundle of productive resources controlled by the organization and by the administrative framework used to organize the use of these productive resources.
Resource degradation – It is a multifaceted concept referring to the environmental damage from natural resources (like air, water, and soil) losing quality and quantity because of improper use and over-exploitation, or the physical or chemical reduction in a manufactured system’s performance over time. It signifies a loss of a resource’s capacity to perform its intended function, leading to ecological imbalance, resource exhaustion, and negative impacts on human livelihoods and economic stability.
Resource depletion – It refers to the exhaustion or substantial reduction of natural resources (like minerals, energy, and water) when they are consumed faster than they can be naturally replenished. It considers the energy needed for extracting lower-quality resources and encompasses the degradation of ecosystems necessary for resource regeneration, making it a key factor in sustainable design and resource management within engineering practices.
Resource intensity – It is the measure of the quantity of resources (such as energy, water, and materials) needed to produce a unit of a good or service. It functions as a key metric for evaluating resource use efficiency, indicating how much input is needed to create a specific output. A lower resource intensity signifies higher efficiency, as fewer resources are consumed for the same production level.
Resource management – It is the process of planning, allocating, and controlling resources to achieve an organization’s goals. Ir is an important aspect in managing the efficient and effective deployment and allocation of the organizational resources when and where they are needed. Resource management needs to be systematized for keeping a close eye on the resources. This process of systematization maximizes the efficiency of the available resources as well as minimizing of the wastage of the resources. Resource management is a fundamental aspect of an organization’s performance.
Resource plans – These plans enable organizations to maximize resource utilization, balance supply and demand and plan resources over the entire period needed for the completion of the planned tasks. Organizations can also use resource plans to identify resources, which could include human, capital, time, or technological equipment needed to achieve strategic goals. Resource plans are used to express resource requirements in terms of resources needed over a period of time. The resource planning provides the organizations the several abilities, which include (i) to increase resource utilization by aligning the right resources to the highest priority work, (ii) to link mission, strategy, work and resources to quickly address changes in budget, mission or environment, (iii) to identify quickly the actions needed to reduce risk and increase performance, and (iv) to conduct more efficient analysis and make better decisions based on current, accurate, integrated, and actionable information.
Resource utilization – It is the measurement of how effectively allocated resources (such as personnel, equipment, time, and financial assets) are being used to achieve project or operational goals, serving as a key metric for optimizing productivity, cost-efficiency, and overall project success. It involves comparing the resources actually used to the total available or potential capacity, identifying whether resources are underutilized, overutilized, or balanced.
Respirator – It is personal protective equipment (PPE) that covers the nose and mouth to prevent the wearer from inhaling hazardous substances like dust, chemicals, fumes, or pathogens from the air. It functions either by filtering contaminants from the ambient air or by supplying clean, independent air to the user. Proper respirator safety needs a thorough risk assessment to identify airborne hazards and determine the appropriate, certified respirator before use, as incorrect selection or use can be ineffective and provide a false sense of security.
Respiratory protection – It refers to using respirators, such as N95 masks or supplied-air respirators, to guard against airborne hazards like dusts, gases, fumes, and mists when other engineering controls like local exhaust ventilation are insufficient or not feasible. It is a critical component of personal protective equipment (PPE) used after elimination, substitution, and other engineering controls have been exhausted, needing a comprehensive respiratory protection programme which includes fit testing, and training.
Respiratory protective equipment – It is used to prevent dangerous chemicals from entering the respiratory system of the wearer. It is also used to provide breathing air when working in a dangerous environment where there is risk of oxygen deficiency or presence of dangerous chemicals in the air at high concentrations. There are three basic classes of respirators which are normally used. They are (i) air purifying respirators, (ii) air supplied respirators, and (iii) self-contained respirators.
Response – It is the provision of emergency services and public assistance during or immediately after a disaster in order to save lives reduces health impacts, ensure public safety and meet the basic subsistence needs of the people affected.
Response curve – It is a graph which visually represents how a system, device, or component reacts to a varying input or stimulus. It plots the magnitude of the system’s response (output) against the magnitude of the input, or stimulus, allowing engineers to analyze and predict performance under different conditions. For example, a microphone’s response curve shows its output at different sound intensities, while a sensor’s response curve illustrates its output for varying input signals.
Response curve for N cycles – In fatigue-data analysis, it is a curve fitted to observed values of percentage survival at N number of cycles for several stress levels, where N is a preassigned number such as 106, 107, etc. It is an estimate of the relationship between applied stress and the percentage of the population which would survive N cycles.
Response delay – It refers to the time lag between when a stimulus is applied to a system and when a response begins to occur. It represents a period of inactivity or processing time within a system, such as a physiological process, a sensor, or a network, before any observable reaction to an input takes place. This delay is also known as reaction time or response latency and is a critical parameter in evaluating system performance and efficiency.
Response factor – In chromatography, a response factor is defined as the ratio between the concentration of a compound being analyzed and the response of the detector to that compound. A chromatogram shows a response from a detector as a peak. While there are several ways to quantify the peak, one of the most common is peak area, hence ‘response factor = peak area / concentration. It is important to remember that variations in a gas chromatography (GC) system and analysis methodology can be the cause of a deviation in the response factor.
Response surface modeling – It is a statistical, mathematical, or graphical model which describes the variation of the response variable in terms of the parameters of the problem.
Response time – It is the time needed for a leak detector or leak testing system to yield a signal output equal to 63 % of the maximum signal attained when tracer gas applied continuously to the system under test. In technology, response time is the time a system or functional unit takes to react to a given input. In computing, the responsiveness of a service, how long a system takes to respond to a request for service, is measured through the response time. That service can be anything from a memory fetch, to a disk input-output, to a complex database query, or loading a full web page. Ignoring transmission time for a moment, the response time is the sum of the service time and wait time.
Restoration – It means returning the health of a facility after a disaster to its original condition.
Restoration costs – These costs are the expenses incurred to return something to its original, functional, or natural state, whether it’s a damaged property, an environmental area, or an asset.
Restoration mechanism – It refers to a system, process, or action taken to return a component, system, or structure from a degraded or failed state back to its intended operational condition or original performance level. This can involve repairing damaged parts, recovering lost information (like in image restoration), re-establishing connections in a failed network, or bringing a structure back to its original state. The specific definition varies by field, but the common thread is the act of recovering or replacing what has been lost or damaged to achieve functionality.
Restoration process – It involves applying techniques and procedures to return a system, structure, or signal to its original condition or to improve its quality after degradation, damage, or failure. This can involve mathematically modeling the original problem and applying an inverse process (like deconvolution in image processing), or physically repairing and rebuilding a deteriorated structure. Example is re-establishing electrical power after an outage.
Rest point – It is a position where a system or object has zero net force and / or zero velocity, resulting in a state of mechanical equilibrium or stability. In physics, this corresponds to a condition where an object is stationary or moves at a constant velocity. In a broader sense, it refers to any fixed or equilibrium state within a system where its behaviour remains constant over time.
Rest potential (Ecorr) – It is the potential of a corroding surface in an electrolyte, relative to a reference electrode. It is also called corrosion potential, open-circuit potential, or freely corroding potential.
Restrained expansion – It is a phenomenon where a material, or a structure, attempts to expand but is prevented from doing so by internal or external constraints, leading to the development of internal tensile stresses and potential structural damage like cracking. This concept is particularly relevant in the construction industry with materials like concrete and in mechanical engineering with components like pipelines and structural joints.
Restrained joint – It prevents the separation of components in a pipeline system, particularly at fittings like bends or tees, by transferring internal pressure (thrust) forces from the pipeline itself to the surrounding soil. Unlike unrestrained joints, which rely on friction alone, restrained joints incorporate mechanical mechanisms, such as wedge-action retainers or locking systems, to create a secure and continuous connection that withstands these forces. This prevents separation in high-stress areas called ‘wiggle zones’ and is crucial for the integrity and safety of pipelines under pressure.
Restrained shrinkage – It is the stress and potential cracking in a material, such as concrete, which occurs when its drying-induced contraction is prevented by internal or external constraints. Unlike free shrinkage, which does not induce stress, restrained shrinkage creates internal tensile forces which can exceed the material’s tensile strength, leading to cracks that compromise structural integrity and durability. Restraints can be caused by reinforcing steel, adjacent structural elements, or even aggregates within the material itself.
Restraint – It is an external mechanical force which prevents a part from moving to accommodate changes in dimension because of the thermal expansion or contraction. It is frequently applied to weldments made while clamped in a fixture.
Restricted area – It is a designated location with limited or controlled access to prevent harm to personnel or damage to assets, typically because of the hazards like toxic exposure, hazardous energy, or risk of injury during emergencies. Restricted areas are set up to control exposure to specific risks, needing authorized personnel and appropriate safety measures, such as personal protective equipment (PPE) or special entry procedures, to ensure the safety of those who are required to enter.
Restricted data – Restricted data definition is a classification for an organization’s most sensitive information, needing the highest level of security controls to prevent unauthorized access and potential legal, financial, or ethical consequences from its exposure or breach. Tit involves designing systems and controls to protect this data throughout its lifecycle, from collection to disposal, ensuring compliance with regulations and internal policies.
Restricted visibility – It is the condition in which visibility is restricted by fog, mist, falling snow, heavy rain-storms, sandstorms or any other similar causes.
Restrictor rings – These are rings, normally faced with white metal, placed outside a bearing to prevent fluid from being discharged.
Restrike – It means compacting of a sintered compact.
Restriking – It is the striking of a trimmed but slightly misaligned or otherwise faulty forging with one or more blows to improve alignment, improve surface condition, maintain close tolerances, increase hardness, or effect other improvements. It is a sizing operation in which coining or stretching is used to correct or alter profiles and to counteract distortion. It is also a salvage operation following a primary forging operation in which the parts involved are rehit in the same forging die in which the pieces have been last forged.
Restructuring of organization – It is the strategic process of changing an organization’s internal structure, reporting relationships, and job designs to improve efficiency, align with new goals, or adapt to market changes. This transformation can involve creating new departments, reassigning roles, or even downsizing the workforce to cut costs and better position the organization for long-term success and growth.
Resuing – It is a method of stoping in narrow-vein deposits whereby the wall-rock on one side of the vein is blasted first and then the ore.
Resultant field – It is the net electric or magnetic field at a point, created by the vector sum of all individual fields from multiple sources. It represents the overall effect of all the individual fields, with its direction determined by the relative strengths and directions of the constituent fields. This concept is also known as a vector field and is based on the principle of superposition.
Resultant flux – It is the net vector sum of multiple individual fluxes acting on or within a system, representing the combined effect of different fields. It can be the combination of fluxes from sources like electric charges, magnetic fields, or multiple current-carrying windings, such as the resultant rotating magnetic field in an induction motor formed by the interaction of individual phase fluxes.
Resultant force – It is a single force which has the same effect on an object as all the forces acting on it combined, and is found by performing a vector sum of all the individual forces. It is also known as the net force, the resultant force is a vector quantity, meaning it has both magnitude and direction. If the resultant force is zero, the object’s motion does not change. If it is non-zero, the object accelerates in the direction of the resultant force.
Retained austenite – It is the quantity of the high-temperature face-centered cubic phase of iron (austenite) which does not transform to martensite (is retained) when quenched to room temperature. It is the austenite which remains in steel after it has been heat treated and quenched. It occurs when the steel is not quenched to a low enough temperature to transform all of the austenite into martensite.
Retainer – It is also called cage or separator. In a bearing, it is a device which partly surrounds the rolling elements and travels with them, the main purpose of which is to space the rolling elements in proper relation to each other.
Retaining ring – It is a split ring which is used to retain a separable flange on a valve body.
Retardant materials – These are substances which resist ignition, slow the spread of fire, or reduce its intensity when exposed to heat or flames. These materials are frequently treated with flame retardants, which are chemicals designed to inhibit burning by either delaying the ignition, cooling the fuel source, or creating a protective char layer. While they can eventually burn if exposed to sufficient heat, their primary function is to improve fire safety and meet fire performance criteria in different applications, from building materials to electronics.
Retardation plate – It is a plate placed in the path of a beam of polarized light for the purpose of introducing a difference in phase. Normally quarter-wave or half-wave plates are used, but if the light passes through them twice, the phase difference is doubled.
Retarder – It is a chemical additive which slows down the rate of a chemical reaction, most commonly the hydration process which leads to hardening in materials like cement or plaster. By forming a protective barrier on particles, or complexing with reacting components, retarders delay the onset of setting, extending the material’s workability and providing more time for placement and finishing, especially in hot conditions. In case of rubbers, retarder is a substance added to rubber compounds to prevent premature vulcanization, or scorching, during processing and storage. It helps control the curing process by being admixed with the compound to avoid pre-curing when subjected to heat.
Retarding admixtures – These admixtures are used to slow the setting of the concrete and to retard temperature increases. They consist of various acids or sugars or sugar derivatives. Retarding admixtures are particularly useful for large pours where significant temperature increases can occur. They also prolong the plasticity of the concrete, enabling better blending or bonding of successive pours. Retarding admixtures can also slow the hydration of cement on exposed concrete surfaces or formed surfaces to produce attractive exposed aggregate finishes.
Retention period – It is a defined length of time for which records, data, or materials is to be stored and maintained, frequently mandated by legal, regulatory, or internal organizational requirements. It can also refer to the time a substance or fluid spends within a system, like hydraulic retention time (HRT), which indicates the period water remains in a reactor, influencing treatment effectiveness.
Retention pond – It is the temporary containment for a material in an area where it can be treated for proper disposal.
Retention time (RT) – It is a measure of the time taken for a solute to pass through a chromatography column. It is calculated as the time from injection to detection. The retention time for a compound is not fixed as several factors can influence it even if the same gas chromatograph and column are used. These include (i) the gas flow rate, (ii) temperature differences in the oven and column, (iii) column degradation, and (iv) column length. These factors can make it difficult to compare retention times. Even if a person uses the same gas chromatograph just a few days apart, there can be small differences in the retention time of a compound.
Retractable stop – It is a mechanism which can be extended to block movement or create a fixed point, and then pulled back into a main component to allow for continuous movement or passage without obstruction. It consists of a movable stop component, frequently a bar or arm, and a retracting system which uses springs, cylinders, or pivoting arms to move the stop. Retractable stops are used in several applications, such as machine tools to position parts, conveyor systems to control product flow, and safety equipment to arrest falls.
Retracting die – It is the part of a method of stripping the compact from the die used.
Retrieval system – It is a computer-controlled, automated mechanism designed to automatically store and retrieve items from a defined location within a warehouse or distribution centre. It is also known as an ‘automated storage and retrieval system’ (ASRS). It uses hardware and software to manage inventory, store goods at high densities, and bring them to operators or conveyor systems. Key components include storage racks, aisles, and specialized machines like cranes or shuttles, and the system improves accuracy, efficiency, and safety by minimizing human interaction.
Retrofitting – It consists of reinforcement or upgrading of existing structures to become more resistant and resilient to the damaging effects of hazards. Retrofitting needs consideration of the design and function of the structure, the stresses which the structure can be subject to from particular hazards or hazard scenarios and the practicality and costs of different retrofitting options. Examples of retrofitting include adding bracing to stiffen walls, reinforcing pillars, adding steel ties between walls and roofs, installing shutters on windows and improving the protection of important facilities and equipment.
Retort – It is a laboratory apparatus which is used for distillation of volatile materials, as in separation of some metals and in destructive distillation of coal. It traditionally consists of a spherical vessel with a long, downward-pointing neck which conducts the condensed vapours produced by distillation into a separate collection vessel.
Retrofit engineering – It involves designing and implementing new features or technologies into existing systems, structures, or processes to improve performance, extend lifespan, increase efficiency, or enhance safety. Instead of building new, the practice adds modern components to older, pre-existing equipment or infrastructure, which can include structural strengthening for buildings, adding new machinery to a factory, or incorporating environmental controls.
Retrofit project – It involves modifying existing structures, systems, or equipment to improve their performance, safety, efficiency, or compliance with new standards, rather than replacing them entirely. Engineers perform a structural or system evaluation, then design and implement remedial measures, which can range from adding new components, reinforcing existing ones, or upgrading outdated systems, to improve structural stability, energy efficiency, safety, or lifespan.
Retrofitting process – It is the process of modifying an existing structure to improve its strength, safety, performance, and functionality. This involves incorporating new technologies, materials, or features to upgrade an outdated design, meet current safety codes, or improve resistance to hazards like earth-quakes, aging, or increased loads.
Retrogressive reactions – These refer to the processes which occur during pyrolysis and liquefaction, characterized by the breakdown and reformation of molecular structures, which can be categorized into fast and slow reactions.
Return air – It is the air which is removed from conditioned spaces that is either recirculated or exhausted to the outside.
Return current path – It is the path through which the current in an electric cell returns to the source.
Return fine – mosaic embedding iron ore sintering (RF-MEBIOS) process – This process has been developed in order to increase the permeability of the sintering bed for sinter ore productivity. The return fine – mosaic embedding iron ore sintering’ process is a technique in which return fine by-passes granulation. In this process, return fine as dry particle is added to granulated raw materials and then charged into the sintering machine which results into productivity increase of the sintering machine. The productivity increase is caused by increasing the pseudo-particle size at granulation and by decreasing the bulk density of the sinter packed bed after charging. The former is achieved by higher moisture content in the raw materials at granulation. The latter is achieved by higher friction in the sintering bed composed of a dry and wet particle compound, which has a role of decreasing bulk density. By increasing the by-pass return fine ratio and size, the sintering speed and sinter productivity is increased.
Return flow oil burner – It is a mechanical atomizing oil burner in which part of the oil supplied to the atomizer is withdrawn and returned to storage or to the oil line supplying the atomizer.
Return Idlers – These idlers support the belt during the return path and meet or exceed the CEMA (Conveyor Equipment Manufacturers Association) load requirements.
Return loss – It is a measure of the power loss because of a signal reflection by a discontinuity in a transmission line or an optical fibre.
Return on Investment (ROI) – It is a financial performance metric which measures the profitability of an investment by comparing the net profit generated to its total cost, expressed as a percentage. It serves as a universal tool to assess an investment’s efficiency or to compare multiple investments, with a higher return on investment normally indicating a more favourable outcome.
Returns – In foundries, it is the metal in the form of gates, sprues, risers or defective castings which are put back into the melting cycle.
Return side – It is the non-carrying belt side towards the pulleys. It is normally thinner than the carry side.
Reusability – It is the property of a component, or a system which allows it to be used multiple times in different projects or applications with minimal or no changes. This concept aims to maximize efficiency and minimize redundancy by avoiding the need to create duplicate solutions for common problems. Reusability can be applied to different engineering assets, including software code, design elements, requirements, and even mechanical components.
Reusable glass – It refers to glass containers which are collected, sterilized, and reused multiple times, with systems in place which promote sustainability through practices like returnable deposit schemes. This model allows for substantial resource conservation, as evidenced by high reuse rates, typically up to 10 times, and a break-even point for breakages which supports their overall efficiency compared to single-use alternatives.
Reuse – It means using items again by repairing, donating, or selling them. Reuse is even better than recycling since the item does not have to be reprocessed before it can be used again.
Reverberatory furnace – It is a long, flat furnace which is used to slag gangue minerals and produce a matte. It is a furnace in which the flame used for melting the metal does not impinge on the metal surface itself, but is reflected off the walls of the root of the furnace. The metal is actually melted by the generation of heat from the walls and the roof of the furnace.
Reversal point – It refers to the point where a system’s behaviour or state changes direction, such as the reversal of a magnetic field, the change in direction of power flow in a direct current system, or the turning point in a mechanical traverse. As an example, a reversal point can be when a rotating component or a winding machine’s traverse reverses its direction, a point where magnetization changes, or a location where a load’s direction reverses on a structure.
Reverse-acting actuator – It is an actuator in which the actuator stem retracts with increasing loading pressure. Reverse actuators have a seal bushing installed in the upper end of the yoke to prevent leakage of the loading pressure along the actuator stem.
Reverse air fabric filters – In these fabric filters, the bags are fastened onto a cell plate at the bottom of the filter and suspended from an adjustable hanger frame at the top. Dirty gas normally enters the filter and passes through the bag from the inside, and the dust collects on the inside of the bags. These filters are compartmentalized to allow continuous operation. Before a cleaning cycle begins, filtration is stopped in the compartment to be cleaned. Bags are cleaned by injecting clean air into the dust collector in a reverse direction, which pressurizes the compartment. The pressure makes the bags collapse partially, causing the dust cake to crack and fall into the hopper below. At the end of the cleaning cycle, reverse airflow is discontinued and the compartment is returned to the main stream. The flow of the dirty gas helps maintain the shape of the bag. However, to prevent total collapse and fabric chafing during the cleaning cycle, rigid rings are sewn into the bags at intervals. Space requirements for a reverse air fabric filter are comparable to those of a mechanical shaker filter. The maintenance needs are somewhat higher.
Reverse bending deformation process – It is based on the principle that steel rod is ductile and the hot rolled scale is brittle. When the rod is deformed, the steel bends, but the hot rolled scale breaks and is released from the surface of the rod and fall away provided the scale is there in sufficient quantity and there is sufficient deformation. The deformation mode is principally bending, but can also include stretching deformation. The equipment for the reverse bending deformation process is to use the principle of reverse bending in a controlled manner to achieve consistent results of scale removal without unduly affecting the properties of the steel rod being descaled. One of the important factors affecting the descaling process is the quantity of total deformation of the steel rod. It is normally considered that the optimum quantity of rod deformation necessary for the complete scale breaking ranges from 8 % to 10 %. Less than 8 % can result in incomplete scale breaking, leaving patches of adherent scale, and more than 10 % normally does not accomplish any additional scale breaking, while at the same time adding an undesirable amount of work hardening to the steel. An additional undesirable effect of heavy deformation (higher than 10 %) is the increased back tension on the rod line which can stretch and neck down the steel rod, affecting rod drafting schedules and requiring more power from the first block to pull the rod through the descaling system. The objective of 8 % to 10 % deformation is controlled by the relationship between the size of the sheaves used to do the reverse bending and the size of the steel rod being processed.
Reversed Brayton cycle – It is also known as the Bell-Coleman cycle or gas refrigeration cycle. It is a thermodynamic process which reverses the gas turbine Brayton cycle to produce cooling. It involves compressing a gas, cooling it in a heat exchanger, expanding it through a turbine or expander to a very low temperature, and then using this cold gas to absorb heat in a low-temperature heat exchanger or evaporator. This cycle is used in refrigeration, air conditioning systems, and the LNG (liquefied natural gas) industry.
Reversed Carnot cycle – It is an ideal, theoretical thermodynamic cycle for refrigeration and heat pumps, consisting of four reversible processes namely adiabatic compression, isothermal heat rejection, adiabatic expansion, and isothermal heat absorption from a cold source.
Reverse-current cleaning – It is the electrolytic cleaning in which a current is passed between electrodes through a solution, and the part is set up as the anode. It is also called anodic cleaning.
Reversed-phase chromatography (RPC) – It is the bonded-phase chromatography with a non-polar stationary phase and a polar mobile phase.
Reverse drawing – It is the redrawing of a sheet metal part in a direction opposite to that of the original drawing.
Reverse engineering – it is also known as backwards engineering or back engineering). It is a process or method through which a person attempts to understand through deductive reasoning how a previously made device, process, system, or piece of software accomplishes a task with very little (if any) insight into exactly how it does so. Depending on the system under consideration and the technologies used, the knowledge gained during reverse engineering can help with repurposing obsolete objects, doing security analysis, or learning how something works.
Reverse extrusion – It is also known as indirect extrusion or backward extrusion. It is a metal-working process where the die is stationary, and the billet (the metal being shaped) and container move together, forcing the metal to flow in the opposite direction of the ram’s movement.
Reverse flange – It is a sheet metal flange made by shrinking, as opposed to one formed by stretching.
Reverse flotation – It is a flotation process where siliceous minerals are floated while iron-bearing minerals are depressed, mainly used for the separation of iron ore. This method is normally less cost-effective and more operationally challenging compared to magnetic separation.
Reverse flow – It refers to the phenomenon where the direction of the liquid flow in a pipe, changes completely, becoming extremely disordered with tangled and meandering paths, as opposed to the smooth and orderly laminar flow. In case of valve, reverse flow is the flow from the shaft / hub side over the back of the disk, ball, or plug. Some rotary control valves are capable of handling flow equally well in either direction. Other rotary designs can need modification of actuator linkage to handle reverse flow.
Reverse helical winding – In filament winding, as the fibre delivery arm traverses one circuit, a continuous helix is laid down, reversing direction at the polar ends, in contrast to biaxial, compact, or sequential winding. The fibres cross each other at definite equators, the number depending on the helix. The minimum region of crossover is three.
Reverse impact test – It is a test in which one side of a sheet of material is struck by a pendulum or falling object, and the reverse side is inspected for damage.
Reverse osmosis (RO) – It is a treatment process which is used in drinking water systems by adding pressure to force water through a semi-permeable membrane. Reverse osmosis removes salinity and majority of the drinking water contaminants and produces a waste stream of highly saline water. It is also used in waste-water treatment.
Reverse osmosis (RO) membrane – It is a thin, semi-permeable barrier made of materials like polyamide, which separates water from dissolved solids, salts, ions, and other impurities under applied pressure. It functions by allowing smaller water molecules to pass through while rejecting larger contaminants, achieving high levels of water purity for applications such as desalination, industrial water treatment, and producing ultra-pure water.
Reverse phase high performance liquid chromatography (RP-HPLC) – It is an analytical technique which uses a non-polar stationary phase (like a hydrophobic silica C18 column) and a polar mobile phase to separate compounds based on their hydrophobicity. In reverse phase high performance liquid chromatography, less polar (hydrophobic) compounds are retained longer by the stationary phase, while more polar (hydrophilic) compounds are eluted first by the polar solvent. This method is crucial in engineering for analyzing and purifying compounds in several fields, such as environmental monitoring, ensuring product quality and safety.
Reverse polarity – It is the arrangement of direct current arc welding leads in which the work is the negative pole and the electrode is the positive pole of the welding arc. It is also known as direct current electrode positive (DCEP).
Reverse probe – It normally refers to a probe or test point which is mounted in a way that makes it harder to access, frequently for protection or to avoid accidental contact, as opposed to a ‘forward probe’ which is easily accessible.
Reverse pulse jet fabric filter – In these filters, individual bags are supported by a metal cage, which is fastened onto a cell plate at the top of the filter. Dirty gas enters from the bottom of the filter and flows from outside to inside the bags. The metal cage prevents collapse of the bag. Bags are cleaned by a short burst of compressed air injected through a common manifold over a row of bags. The compressed air is accelerated by a venturi nozzle mounted at the reverse jet filter top of the bag. Since the duration of the compressed-air burst is short (0.1 second), it acts as a rapidly moving air bubble, traveling through the entire length of the bag and causing the bag surfaces to flex. This flexing of the bags breaks the dust cake, and the dislodged dust falls into a storage hopper below. Reverse pulse jet fabric filters can be operated continuously and cleaned without interruption of flow because the burst of compressed air is very small compared with the total volume of dusty air through the collector. Because of this continuous cleaning feature, these filters are normally not compartmentalized. The short cleaning cycle of these filters reduces recirculation and redeposit of the dust. These filters provide more complete cleaning and reconditioning of bags than shaker or reverse air cleaning methods. Also, the continuous-cleaning feature allows them to operate at higher air-to-cloth ratios, so the space requirements are lower. This cleaning system works with the help of digital sequential timer attached to the fabric filter. This timer indicates the solenoid valve to inject the air to the blow pipe.
Reverse reaction – It is the backward process within a reversible chemical reaction, where the products of a reaction convert back into the original reactants. This occurs simultaneously with the forward reaction (reactants forming products) in a reversible system, eventually leading to a state of dynamic equilibrium where the rates of both the forward and reverse reactions are equal.
Reverse redrawing – It is s second drawing operation in a direction opposite to that of the original drawing.
Reverse sigmoid curve – It refers to the inverse of the sigmoid function. It is also known as the logit function or log-odds function, which maps a probability (0 to 1) to a real-valued log-odds.
Reversible conveyor belt – It is a type of conveyor system which can change its direction of travel, offering flexibility in material handling and storage applications. The main characteristic is the ability to switch the direction of material flow, allowing for movement in both directions.
Reversible phase transition – It is a material’s ability to cycle between distinct structural or physical states (phases) and return to its original state without permanent changes, triggered by external stimuli like temperature, pressure, or electric fields. This ability is important for developing functional materials and devices, such as phase-change memory and sensors, since it allows for controllable and dynamic material behaviour.
Reversible process – It is a process, involving a system and its surroundings, whose direction can be reversed by infinitesimal changes in some properties of the surroundings, such as pressure or temperature.
Reversible reaction – It is a chemical reaction which can proceed in either direction depending on the reaction conditions, i.e., from reactants to products or from products to reactants, especially implying one in which both conversions occur simultaneously.
Reversible temper embrittlement – It is a phenomenon in certain alloy steels where holding or slowly cooling through a specific temperature range (around 400 deg C to 600 deg C) leads to a loss of ductility and toughness, but this embrittlement can be reversed by reheating above 600 deg C and rapid cooling.
Reversible thermal expansion – Refractories like any material expand when heated, and contracts when cooled. The reversible thermal expansion is a reflection on the phase transformations which occur during heating and cooling. The reversible expansion are followed in the design of refractory lining for provision of expansion joints. As a rule, those with a lower thermal expansion co-efficient are less susceptible to spalling.
Reversing mills – These are those rolling mills in which the rolling direction changes after each pass. In these mills the rolls are stopped, reversed, and then brought back up to rolling speed after each pass. In these mills the material is being rolled moves in to and fro directions. Heavy primary mills for bloom and slab rolling are the most common types of reversing mills, but others, including some cold rolling mills, are also reversing mill.
Reversing roller conveyor – In a reversing processing conveyor, the direction of rotation of the driven rollers is changed frequently. As a result, the additional inertial forces for accelerating or decelerating the rollers and the load have to be taken into consideration. The maximum peripheral acceleration of the roller is kept within limits, such that the load moves on rollers without sliding (also called skidding). There is no sliding when the frictional force between roller and load is more than the inertial force needed to accelerate the load.
Reversing shuttle conveyor – It is used for building an in-line, continuous pile, or for feeding multiple fixed discharge points. Similar in form to a troughed belt conveyor, reversing shuttle conveyors are designed with traveling shuttle functionality. The shuttle functionality allows the conveyor to be moved along a track, as well as convey material in both directions, creating opportunity for extreme flexibility. The conveyor is typically half the length of the track rails, e.g., a 100 meters long shuttle conveyor has the ability to transport material throughout the length of a 200 meters storage facility.
Reversing valve – It is also called a 4-way valve. It is a component which changes the direction of refrigerant flow in a heat pump or air conditioner to allow the system to switch between heating and cooling modes. By altering the path of the refrigerant, the valve enables a single piece of equipment to provide both functions, making the heat pump system more versatile. It has four ports which connect to the compressor, indoor coil, and outdoor coil, with its internal valve stem controlled by a solenoid or a pressure differential to direct the hot or cold refrigerant to the appropriate coil.
Revert – In foundries, it consists of recycled sprues, gates, risers, defective castings and machine chips.
Revert scrap – It is also called home scrap or internal scrap. It is the internally generated scrap during the production of the new steel products in the steel plants and the steel foundries. This form of the steel scrap rarely leaves the steelmaking production area. Instead, it is returned to the steelmaking furnace on the plant site and melted again. Technological advancements have considerably reduced the generation of revert scrap.
Review process – It is a structured and systematic evaluation conducted at different project stages to ensure that designs, products, or processes meet established standards, requirements, and objectives. It involves identifying and correcting defects, assessing current condition, verifying data, and ensuring stakeholder alignment, ultimately aiming to improve quality, reduce costs, and prevent failures. Key types include technical peer reviews, document reviews, and critical design reviews, which serve as vital checkpoints in the engineering lifecycle. Review is also a systematic evaluation to ensure a component can perform its design function reliably over a specified time frame, involving inspections and testing to assess its current condition and verifying data through competent oversight.
Review techniques – These techniques encompass structured processes, such as the ‘programme evaluation and review technique (PERT) and ‘formal technical reviews’ (FTR), designed for systematic evaluation and analysis to ensure project success, identify errors, and improve quality.
Revision block – In an engineering drawing, it is a table which records the history of changes made to the drawing after its initial issue, detailing the revision number, date, a description of the changes, and who approved them. This block, typically located in the upper right-hand corner or near the title block, is crucial for maintaining version control, ensuring users have the most current version of the drawing, and tracking the design’s evolution.
Revolute joint – It is also known as a hinge joint. It is a joint which allows one relative rotational degree of freedom (DOF) between segments, enabling rotation around the joint axis while preventing relative translations.
Revolution joint – It is a type of joint which allows rotational movement between two components, characterized by the alignment of their axes and the specification of their origins to maintain their original positions.
Reward system – It is a set of incentives which is given in exchange for specific behaviours, actions, or achievements. It can be used to motivate employees, encourage customers, or promote healthy competition.
Rework – It is an action taken on non-conforming products or services to allow them to meet the original specifications.
Reyn – It is the former English unit of dynamic viscosity.
Reynold’s equation – It is a basic equation of hydrodynamic lubrication.
Reynolds number (Re) – It is a dimensionless quantity which helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces. It is a derived relationship combining the density and viscosity of a liquid with its velocity of flow and the cross-sectional dimensions of the flow and takes the form R = (V x D x d)/v, where ‘V’ is the average fluid velocity, ‘D’ is the diameter of the pipe, ‘d’ is the density of the liquid, and ‘v’ is the absolute viscosity. At low Reynolds numbers, flows tend to be dominated by laminar (sheet-like) flow, while at high Reynolds numbers, flows tend to be turbulent. The turbulence results from differences in the fluid’s speed and direction, which can sometimes intersect or even move counter to the overall direction of the flow (eddy currents). These eddy currents begin to churn the flow, using up energy in the process, which for liquids increases the chances of cavitation. The Reynolds number has wide applications, ranging from liquid flow in a pipe to the passage of air over an aircraft wing. It is used to predict the transition from laminar to turbulent flow and is used in the scaling of similar but different-sized flow situations. The predictions of the onset of turbulence and the ability to calculate scaling effects can be used to help predict fluid behaviour on a larger scale, such as in local or global air or water movement, and thereby the associated meteorological and climatological effects.
Reynolds stress – It refers to the components of the turbulent stress tensor that result from the averaging process applied to the Navier-Stokes equations in turbulent flows, representing additional effective momentum fluxes caused by unsteady turbulent velocity fluctuations. These stresses quantify the momentum transfer because of the chaotic, irregular motions of turbulence, acting as additional shear and normal stresses which are important for accurately modeling and predicting the behaviour of turbulent flows in several engineering applications.
R-factor It is also called residual factor or reliability factor or the R-value. It is a measure of the disagreement between the crystallographic model and the experimental X-ray diffraction data. Lower is the R-value lower is the disagreement or better is the agreement. In other words, it is a measure of how well the refined structure predicts the observed data. The value is also sometimes called the discrepancy index, since it mathematically describes the difference between the experimental observations and the ideal calculated values.
RF connector – It is an electrical fitting which is used to connect cables carrying radio frequency (RF) currents.
RF engineering – It is the profession which deals with application of radio frequency (RF) energy to useful ends.
RH degassing process – RH degassing process has been named after Ruhrstahl and Heraeus where this process was initially developed. It is normally used for mass production of steel in order to reduce gases and carbon contents in the liquid steel. The main functions of RH degassing plant is the removal of hydrogen, natural and forced decarburization, chemical heating of the liquid steel, and for the precise adjustment of the chemical analysis and temperature of the liquid steel. These activities are carried out under vacuum conditions. The selection of RH degassing is strictly dictated by steel grades to be produced in the steel plant. In the majority of the cases, the installation of RH degassing is more dominant, especially for big heat size, because of its excellent mixing performance, and short cycle time for decarburization and degassing which results into a large number of heats treated per day. Further, due to the excellent mixing behaviour achieved during the process, this short treatment time is attainable irrespective of the size of the ladle. A lot of process improvements have been done on the RH degassing plant since its introduction. These improvements include the installation of oxygen lance, the enlargement of snorkel and vessel diameters, as well as the application of powder injection for desulphurization. When equipped with an additional top-lance, the RH degassing is called RH-TOP degassing. RH degassing unit typically consists of a refractory lined block-type or split-type vessel, equipped with two refractory lined snorkels at the vessel bottom, which is connected to a vacuum pump. Further components are a hydraulic or mechanical vessel or ladle lifting system, in case of an RH-TOP, a multiple function top blowing lance, and a measuring and sampling system. Material addition under vacuum is executed by means of a vacuum hopper system. Refractory repair and preheating of vessels, snorkels and top part can be executed in separate stands. Characteristics of the design are the single vessel installation (vessel lifting system), fast vessel exchange (ladle lifting system) or duplex vessel installation for increased availability. Comprehensive model for decarburization on RH degassing plant has been introduced by Kuwabara considering the vacuum pressure, lift gas flow rate, vessel as well snorkel diameters. It has been reported that the time needed to achieve carbon content of less than 20 ppm (parts per million) can be completed in less than 15 minutes in a RH degassing plant.
Rhenium (Re) – It is a chemical element having atomic number 75. It is a silvery-gray, heavy, transition metal. With an estimated average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the earth’s crust. It has one of the highest melting and boiling points of any element. It resembles manganese and technetium chemically and is mainly obtained as a by-product of the extraction and refinement of molybdenum and copper ores. It shows in its compounds a wide variety of oxidation states ranging from −1 to +7.
Rheocasting – It is the casting of a continuously stirred semi-solid metal slurry. The process involves vigorous agitation of the melt during the early stages of solidification to break up solid dendrites into small spherulites.
Rheodynamic lubrication – It is a regime of lubrication in which the rheological (non-Newtonian) properties of the lubricant predominate. This term is especially applied to lubrication with grease.
Rheological flow – It refers to the continuous deformation or movement of a material, such as a liquid, gas, or even a solid, when subjected to an applied force or stress. It is a key aspect of rheology, the branch of physics which studies how matter deforms and flows. The properties which govern this behaviour, known as rheological properties, describe the relationship between applied forces, the resulting deformation or flow, and the time over which these occur.
Rheological property – It defines a material’s response to applied forces or stresses, characterizing its flow and deformation behaviour, including properties like viscosity, elasticity, and plasticity. Understanding these properties is important for designing processes, equipment, and products that involve the movement and handling of materials like concrete, drilling fluids, foods, and blood, since they determine how materials behave under different conditions.
Rheology – It is the study of the flow of matter, mainly in a fluid (liquid or gas) state but also as soft solids or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an applied force. Rheology deals with the deformation and flow of materials, both solids and liquids.
Rheometer – It is an instrument which measures the flow and deformation properties of a material under stress or strain, enabling engineers to understand its rheology, or the science of flow. It provides critical data on viscosity and modulus, allowing for the characterization of complex fluids and soft solids like polymer melts, and paints, helping to optimize manufacturing processes and predict material behaviour.
Rheopectic material – It is a material which shows an increase in viscosity with time under a constant shear stress. After removal of the shear stress, the viscosity slowly returns to its original level.
Rheoscope – It is obsolete name for an ammeter; now an instrument for measuring fluid viscosity.
Rheostat – It is obsolete name for a two terminal variable resistor, normally with a rotating shaft to allow manual or motor driven adjustment.
Rhodium (Rh) – It is a chemical element having symbol Rh and atomic number 45. It is a very rare, silvery-white, hard, corrosion-resistant transition metal. It is a noble metal and a member of the platinum group. It has only one naturally occurring isotope, which is 103Rh.
Rhombohedron I It is also called a rhombic hexahedron or, inaccurately, a rhomboid. It is a special case of a parallelepiped in which all six faces are congruent rhombi. It can be used to define the rhombohedral lattice system, a honeycomb with rhombohedral cells. A rhombohedron has two opposite apices at which all face angles are equal; a prolate rhombohedron has this common angle acute, and an oblate rhombohedron has an obtuse angle at these vertices. A cube is a special case of a rhombohedron with all sides square.
Rhombohedral – It is having three equal axes, with the included angles equal to each other, but not equal to 90-degree.
Rhombohedral crystal – It is defined as a crystal structure with a rhombohedral shape and a specific arrangement of atoms, such as Bi2Se3, which shows a layered structure with a hexagonal lattice within each layer.
Rhombohedral crystal system – It is also known as the trigonal system. It is a crystal system characterized by three equal and interchangeable axes at equal angles to each other, and is frequently considered a division of the hexagonal system.
Rhyolite – It is a fine-grained, extrusive igneous rock which has the same chemical composition as granite.
Rib – It is a long V-shaped or radiused indentation which is used to strengthen large sheet metal panels. It is also a long, normally thin protuberance which is used to provide flexural strength to a forging (as in a rib-web forging).
Rib height – It is a physical measurement of a raised, structural element, defined as the distance between the highest point of the rib and the core surface it is connected to, or from which it originates. The concept of rib height is used in different contexts, including ribbed steel bars, injection molded plastic parts, and architectural structures.
Rib mark – It is a curved line on a crack surface, normally convex in the general direction toward which the crack is running. The term is useful in referring to a mark of this shape until its specific nature is learned.
Rib samples – Theses sample consist of ore taken from rib pillars in a mine to determine metal content.
Rib spacing – It refers to the distance between two adjacent ribs, a term used in different fields including construction, and mechanical engineering, where it describes the distance between structural elements that provide support, stiffen surfaces, or improve heat transfer. For example, in a ribbed slab, it is the space between the concrete beams, while in ribbed reinforcement bars, it is the distance between the raised patterns on the steel’s surface.
Rib stiffened panels – These are structural elements which incorporate stiffeners to improve their load-bearing capacity by distributing stresses more effectively, hence preventing bending and increasing overall durability.
Rice husk – It is also called hull. It is the protective outer covering of the rice grain, removed during the milling process, and it is composed of silica, lignin, and cellulose. Though it has no nutritional value for humans, it is a versatile by-product with applications in agriculture for soil conditioning and water retention, as a material for building and insulation, as a fuel source, and even as a component for making pozzolanic ash for cement.
Rice husk ash – It is a fine, grey-to-white ash produced from the controlled burning of rice husks, the protective outer coverings of rice grains. This agricultural by-product is rich in silica, making it a valuable pozzolanic material used in industries like construction to improve concrete strength and durability. It also serves as a thermal insulator and finds applications in the production of ceramics, plastics, and other industrial materials.
Rich phase – It refers to a distinct portion of a system, such as a polymer or alloy, which has a higher concentration of a specific component, resulting from phase separation. Ads an example, in a polymer blend, a ‘polymer-rich phase’ has more polymer than the other phase, which is ‘polymer-poor’ or ‘solvent-rich’. Similarly, in a metallic alloy, an ‘Al-rich phase’ contains a higher proportion of aluminum than other phases present.
Rich slag – It is a byproduct produced during the refining of iron and steel from vanadiferous iron ores, which contains substantial quantities of vanadium and can be processed for vanadium extraction using methods such as salt roasting and water leaching.
Richter scale – It is the most common standard of measurement for earth-quakes. It is used to rate the magnitude of an earthquake, which is the quantity of energy released during an earthquake. he Richter scale does not measure quake damage which is dependent on a variety of factors including population at the epi-centre, terrain, depth, etc. The Richter magnitude involves measuring the amplitude (height) of the largest recorded wave at a specific distance from the seismic source. Adjustments are included for the variation in the distance between the various seismographs and the epicentre of the earthquakes. The Richter scale is a base-10 logarithmic scale, meaning that each order of magnitude is 10 times more intensive than the last one. In other words, a two is 10 times more intense than a one and a three is 100 times higher. In the case of the Richter scale, the increase is in wave amplitude. That is, the wave amplitude in a level 6 earthquake is 10 times higher than in a level 5 earthquake, and the amplitude increases 100 times between a level 7 earthquake and a level 9 earthquake. The quantity of energy released increases 31.7 times between whole number values.
Riddle – It is hand-operated or power-operated device for removing large particles of sand or foreign material from foundry sand.
Ridging (wear) – It is a deep form of scratching in parallel ridges normally caused by plastic flow of the subsurface layer.
Riding rings – The riding rings provide a surface for the kiln load to be distributed. They help in supporting the furnace shell and are one-piece steel castings. Field-welded riding rings have also been used. Riding rings up to a diameter of 5 meters are welded to the shell in some designs. Toothed riding rings are also common. Normally, however, especially in large-diameter kilns, riding rings are slipped loosely onto the thickened shell ring. The riding ring moves relative to the shell when in rotation. Correct sizing of the riding ring, play, and shell ring thickness are crucial for lining life in a kiln section. This represents a difficult design problem. Measurements of oval deformation with the ‘shell tester’ help the designer. Most of the kilns are supported at several points. Careful installation and maintenance of kilns are important. The alignment of long rotary kilns is critical for the load distribution on the riding rings and the shell.
Riemann problem – It is a fundamental initial value problem for hyperbolic partial differential equations, particularly conservation laws, which involves an initial condition with a single discontinuity separating two distinct, constant states. Solutions typically consist of shock waves, rarefaction waves, and contact discontinuities and are critical for understanding nonlinear wave propagation in fields like computational fluid dynamics (CFD) and for developing and testing numerical methods, such as finite volume methods and Riemann solvers.
Rigger – Rigger is a skilled tradesperson who specializes in using rigging equipment and techniques to safely secure and move heavy loads using cranes, hoists, and other lifting devices.
Rigging – It consists of the engineering design, layout, and fabrication of pattern equipment for producing castings, including a study of the casting solidification programme, feeding and gating, risering, skimmers, and fitting flasks. In handling of materials, rigging is both a noun, the equipment, and verb, the action of designing and installing the equipment, in the preparation to move objects. A team of riggers design and install the lifting or rolling equipment needed to raise, roll, slide or lift objects such as heavy machinery, structural components, building materials, or large-scale fixtures with a crane, hoist, or a block and tackle. Rigging comes from rig, to set up or prepare. Rigging is the equipment such as wire rope, turn-buckles, clevis, jacks which is used with cranes and other lifting equipment in material handling and structure relocation. Rigging systems normally include shackles, master links and slings, and lifting bags in underwater lifting. In foundries, rigging consists of gates, risers, loose pieces, etc., needed on the pattern to produce a sound casting.
Right angle – It is an angle which measures exactly 90-degree, formed when two lines or rays meet at a point known as the vertex and are perpendicular to each other. It represents a quarter of a full turn or rotation and is visually depicted by a square symbol at the vertex, differentiating it from other angles.
Right-angled triangle – It is a triangle which has one angle measuring exactly 90-degree, also known as a right angle. The side opposite the right angle is the longest side and is called the hypotenuse. The other two sides, which form the right angle, are called legs and can be referred to as the base and height.
Right hand lang lay – In wire rope construction, a right-hand lang lay (RHLL) means the strands are twisted clockwise around the core, and the wires within those strands are also twisted in the same clockwise direction.
Right hand lay – In wire rope construction, right-hand lay refers to the direction in which the strands are twisted around the core, with the strands appearing to rotate clockwise when viewed from the end.
Right-hand ordinary lay (RHOL) – It is also known as a right-hand regular lay. It is a type of wire rope where the individual wires within the outer strands are twisted in the opposite direction to the strands themselves, resulting in a clockwise (right-hand) twist of the strands around the core. similar to a right-hand screw thread.
Right-hand regular lay – In right hand regular lay rope, the wires within the strands are twisted in the opposite direction to the strands themselves, resulting in the wires running along the axis of the rope, and the strands twisting in a right-hand (clockwise) direction.
Right-hand rule – It is a mnemonic (designed to aid the memory) device for remembering the definitions of the directions of current and magnetic field in generators. Right-hand side (RHS) – It refers to the expression or value on the right side of an equation’s equals sign, but can also denote the use of the right hand to establish a standard orientation or direction for a system of coordinates or for the relationship between vectors, like in the right-hand rule used for electro-magnetism or calculating cross products.
Right-of-way (ROW) – It is the legal strip of land designated for public use, such as constructing and maintaining roads, railways, pipelines, and utility lines. It provides the necessary corridor for infrastructure development and includes not just the roadway but also sidewalks, drainage, and space for future expansion or utilities. The width of a right-of way is determined by the type of infrastructure, ensuring it accommodates the roadway, future development, and necessary components like drainage and utilities.
Rigid body – It is a solid body in which deformation is zero or negligible, when a deforming pressure or deforming force is applied on it. The distance between any two given points on a rigid body remains constant in time regardless of external forces or moments exerted on it. A rigid body is normally considered as a continuous distribution of mass.
Rigid container sheet – In the context of packaging, it refers to a firm, non-flexible sheet material used to create containers which retain their shape and provide protection to the contents, unlike flexible packaging.
Rigid couplings – These couplings are used for shafts having no misalignment. Since these couplings cannot absorb any misalignment the shafts to be connected by a rigid coupling must have good lateral and angular alignment. As compared with flexible couplings, rigid couplings have limited application. Rigid couplings do not have the ability to compensate for shaft misalignments and are therefore used where shafts are already positioned in precise lateral and angular alignment. Any misalignment between shafts will create high stresses and support bearing loads. Rigid couplings are typically used in applications involving vertical drivers. The rigid coupling transmits not only the rotational motion from the driver (typically an electric motor) to the rotating element of the equipment, but any axial movement (up or down) which occurs between the two pieces of equipment is also transmitted between them. Because of rigidity of the couple, the equipment must be in precise alignment and cannot accept any misalignment.
Rigid frame – It is a structural system where linear members, such as beams and columns, are connected by rigid or moment-resisting joints, allowing the entire structure to act as a single, stable unit capable of resisting both vertical and lateral loads through axial forces, shear forces, and bending moments. The key characteristic is the stiffness of the connections, which prevent substantial rotation or deformation at the joints, leading to higher stability and resistance to loads like wind and earthquakes.
Rigid joint – It is a structural connection which prevents any relative translation or rotation between the members it connects, hence maintaining the original angle between them even under load. These joints transmit forces and moments across the connection and are used in structures like frames to create more rigid and statically indeterminate systems, leading to lighter and stronger designs compared to structures with pinned (hinged) joints.
Rigid packaging – It is designed to be protective and withstand potential impact without breaking or compromising integrity. For this reason, rigid containers are typically used to store products which need special protection against damage, heat, light, odours, and more.
Rigid structure – It is a construction designed to resist deformation like bending, twisting, or stretching under applied loads, hence maintaining its shape and stability. This inherent stiffness is achieved through rigid connections between structural members (such as beams and columns in a rigid frame) and strong, durable materials, which allow the structure to carry loads effectively through axial forces, shear, and bending moments.
Rigid termination – It is an electrical signal’s end in a transmission line where the termination device has infinite impedance, causing the entire signal to be reflected back as if the line ended in a wall. This is a conceptual opposite to matching termination (using a termination resistor equal to the line’s characteristic impedance), which absorbs the signal to prevent reflections. While no physical component can be infinitely rigid or have infinite impedance, the concept of rigid termination in signal analysis treats the end of a line as a perfectly reflecting, immovable surface.
Rigorous analysis – It is the systematic and meticulous application of precise standards, established methods, and logical principles to thoroughly examine a system, process, or data to understand its behaviour, identify flaws, and draw accurate conclusions. It involves detailed investigation, careful execution of procedures, and the use of relevant theories to ensure a deep and unbiased evaluation of a subject, leading to trustworthy and reproducible insights.
Rimmed steel – It is a low-carbon steel containing just enough iron oxide to produce a “rimming” action during solidification, which involves the continuous evolution of carbon mono-oxide gas from the reaction of dissolved iron oxide and carbon. This process creates an outer skin, or ‘rim’ of purer iron, while the central core is richer in impurities. The resulting defect-free, low-carbon rim is ideal for processes like deep drawing, spinning, and rolling, where a clean surface and good formability are important for producing products like steel sheets and plates.
Rimming steel – It is a low-carbon steel containing sufficient iron oxide to give a continuous evolution of carbon mono-oxide while the ingot is solidifying, resulting in a case or rim of metal virtually free of voids. These are steels possessing a rim of purer material (with maximum freedom from surface defects) and is associated with evolution of carbon mono-oxide gas occurring because of the interaction of dissolved iron oxide and carbon during the solidification of low carbon and low manganese steel made under controlled deoxidation. The composition and extent of the rim can be varied and, if needed, by arresting the rimming action after sometime. This steel can be produced with an outer layer of very pure iron which gives rise to a sheet and strip products with excellent surface quality and good formability. The widespread adoption of the continuous casting process has resulted in rimming steels generally being replaced by killed steels.
Ring and circle shear – It is a cutting or shearing machine with two rotary-disk cutters driven in unison and equipped with a circle attachment for cutting inside circles or rings from sheet metal, where it is impossible to start the cut at the edge of the sheet. One cutter shaft is inclined to the other to provide cutting clearance so that the outside section remains flat and usable.
Ring compression type couplings – The coupling consists of two cones which are placed on the shafts to be coupled and a sleeve that fits over the cones. Three bolts are used to draw the cones towards each other and thus wedge them firmly between the shafts and the outer sleeve.
Ringelmann chart – It is a series of four rectangular grids of black lines of varying widths (shade 2 to shade 5) printed on a white background, and used as a criterion of blackness for determining smoke density in stack gas streams. Shade 1 is slightly grey and is normally categorized by air pollution boards as acceptable.
Ringelmann scale – It is also called Ringelmann smoke chart, or simply Ringelmann chart. It is a scale for measuring the apparent density or opacity of smoke. The scale has 5 levels of density inferred from a grid of black lines on a white surface which, if viewed from a distance, merge into known shades of grey. Shade 1 is slightly grey and is normally categorized by air pollution boards as acceptable. It corresponds to an opacity of 20 %. Shades 2, 3, 4 and 5 correspond to opacities of 40 %, 60 %, 80 % and 100 % (completely black) and are normally considered to be ‘black smoke’ by air pollution boards of majority of the countries.
Ring forging – It also called rolled ring forging. It is a metalworking process which produces seamless, high-strength rings by heating a metal preform and then manipulating it between opposing rollers to form a circular shape with improved grain structure and mechanical properties. This process creates durable, high-quality rings used in critical applications across industries, where performance and reliability are essential.
Ring gauge – It is a cylindrical, ring-shaped inspection tool used in manufacturing to check the external diameter of cylindrical objects like pins, shafts, and fasteners. It is a type of limit gauge which provides a quick ‘go’ or ‘no-go’ judgment, indicating if a part’s diameter falls within specified tolerances without needing a micrometer or caliper. It is made from durable, thermally stable materials like steel. Ring gauges are designed with high precision and are critical for quality control in several industries.
Ring groove – It is a precision-machined recess or channel within a component, such as a piston or flange, designed to hold and facilitate the function of a sealing ring, like a piston ring or O-ring. These grooves are engineered with specific dimensions and tolerances to ensure the ring can effectively seal, flex, rotate, and handle operating pressures, preventing leakage while maintaining proper function of the component.
Ring joint facing flange – It is also known as RTJ flange. It is normally used for a leak-proof connection in high pressure applications. The flange has a hexagonal groove sealing surface and is fitted with a metal ring which is compressed in a groove.
Ring rolling – It is one of the metal-forming operations which decreases the thickness (cross section) and increases the diameter (circumference) of the work-piece by squeezing effect as it passes between two rotating rolls. It is an advanced technique, extensively used to produce seamless rings which are normally being used as flanges, pipe flanges, ring gears, structural rings, gas-turbine rings, nuclear reactor parts, aero-engine casing, and different connecting flanges. Ring rolling is an incremental bulk metal forming process used for the production of seamless rings with a wide variety of sizes and shapes as well as processable materials, which allows application of rolled rings in several industries. The process works by reducing a pre-formed cross-sectional area of a ring in two roll gaps, increasing its diameter. For achieving this, a non-driven mandrel moves in the direction of the rotationally driven main-roll in the radial roll gap, reducing the wall thickness of a ring. Also, two driven conical rolls located vertically on the opposite side of the machine shape the axial roll gap, in which the height of the ring is reduced by downwards movement of the upper roll. Two guide rolls ensure circularity as well as alignment of the ring in the machine by inducing lateral forces aiming inwards on both sides of the axis of the machine.
Ring rolling mills – In the ring rolling mills, the donut shape pre-formed work piece is placed between a free turning inside roll and a driven outside roll. The ring rolling mills make the section thinner while increasing the ring diameter. Several cross-sections can be formed by the ring rolling.
Ring seal – It is a piston ring-type seal which assumes its sealing position under the pressure of the fluid to be sealed.
Ring spring – It is a special type of mechanical spring comprising a stack of interlocking inner and outer conical rings which absorb and dissipate energy through friction, rather than solely elastic deformation. Under compressive load, the wedge-like action of the conical interfaces causes the outer rings to expand and the inner rings to contract, resulting in sliding across the mating surfaces. This process generates substantial friction, allowing ring springs to act as effective damping systems or energy storage devices, particularly in applications needing a compact size and high energy absorption capacity.
Ring type joint (RTJ) – Ring type gaskets are to be used on the flanges with this type of facing. This type of facing is used in severe service conditions and for hazardous fluids. It is used in petroleum, petrochemical and high-pressure gas pipe work and equipments. Since close tolerances and high standards of machining are required, as a result this type of flange facing is seldom used for flange diameters larger than 900 millimeters. The main disadvantage of this type of facing is the high cost of manufacturing. It is the most expensive face.
Rinsability – It is the relative ease with which a substance can be removed from a metal surface with a liquid such as water.
Rinse water – It is the solvent (typically high-quality water, but potentially including other liquids) used to remove or dilute residues from a process or surface, ensuring cleanliness and preventing cross-contamination between steps. Its specific definition and requirements vary by industry, such as removing process chemicals in metal finishing, diluting contaminants in electronics manufacturing, or clearing residual samples in laboratories.
Rinsing – It is removing of any active solution from the surface of steel by immersion in water rust, corrosion product consisting of hydrated iron oxides.
Rip detection – It is a system detecting a lengthwise damage of the conveyor belt. Most common are sensor loops embedded in the belt’s cover at a certain spacing. Also other external such as X-ray, mechanical, radiant or optical systems can be used.
Ripple – It is a periodic variation in the amplitude of a direct current signal, such as found in a power supply with partly effective filtering. It is the regular modulations in the direct current output wave of a rectifier unit, or a motor-generator set, originating from the harmonics of the alternating current input system in the case of a rectifier, or from the harmonics of the induced voltage of a motor-generator set.
Ripple current – It refers to the unwanted alternating current component which remains in the output current of a power supply, typically after rectification and filtering, and can lead to increased heat dissipation and potential failure of components like capacitors.
Ripple formation – It is the formation of periodic ridges and valleys transverse to the direction of motion on a solid surface. It is also referred to as rippling.
Ripple mark – It is a rib mark with wavelike contour caused by temporary excursion of the crack front out of plane in response to a tilt in the axis of principal tension induced by an elastic pulse. Such marks frequently appear as a series of curved lines, indicating the direction of propagation of the fracture from the concave to the convex side of a given Wallner line, and are sometimes observed when viewing brittle fracture surfaces at high magnification in an electron microscope. Wallner lines are attributed to interaction between a shock wave and a brittle crack front propagating at high velocity. Sometimes a ripple mark is misinterpreted as a fatigue striation. It is also known as Wallner line.
Ripple voltage – It is the residual periodic variation of the direct current voltage within a power supply which has been derived from an alternating current source. This ripple is because of the incomplete suppression of the alternating wave-form after rectification. Ripple voltage originates as the output of a rectifier or from generation and commutation of direct current power.
Rip protection – It is a system to prevent the intrusion of foreign bodies into the belt and its subsequent slitting. This can be done by a simple breaker (a fabric ply) or single synthetic transverse cords.
Rip protection steel cord conveyor belt – This type of belt provides excellent rip protection and impact resistance, minimizes damage to belt carcass from sharp objects or strong impact, and prevents the belt from being torn lengthwise by sharp objects inserted between the belt and other equipment. .
Riser – It is a reservoir of molten metal connected to a casting to provide additional metal to the casting, needed as the result of shrinkage before and during solidification. Riser is also that section of pipeline extending from the ocean floor up the platform. Also, it is the vertical tube in a steam generator convection bank that circulates water and steam upward.
Riser, blind – It is a riser which does not break through the top of the cope and is entirely surrounded by sand. It is opened to the atmosphere by means of a firecracker core.
Riser blocks – These are plates or pieces inserted between the top of a metal forming press bed or bolster and the die to decrease the height of the die space. (It is also the spacers placed between bed and housings to increase shut height on a four-piece tie-rod straight-side press.
Riser contact – It is the connecting passage between a riser and a casting.
Riser design – It is also known as risering. It deals with the development of suitable reservoirs of feed metal in addition to the desired casting shape so that undesirable shrinkage cavities in the casting are eliminated or moved to locations where they are acceptable for the intended application of the casting. When metals solidify and cool to form a casting, they normally undergo three distinct stages of volume contraction, or shrinkage. These stages are (i) liquid shrinkage which means that the liquid metal loses volume as it gives up superheat and cools to its solidification temperature, (ii) solidification shrinkage which takes place when the metal freezes, i.e., changing from a liquid to a higher-density solid (for pure metals, this contraction occurs at a single temperature, but for alloys it takes place over some range of temperature or freezing interval), (iii) solid shrinkage which takes place when the solid casting cools from its solidification temperature to room temperature. The last of these, solid shrinkage (also called patternmaker’s shrinkage), is accommodated by making the pattern (and hence the mould cavity) somewhat larger than the desired dimensions of the final casting. Liquid shrinkage and solidification shrinkage are the concern of risering practice.
Riser distance – It is the length of the riser neck. The term is applied to side risers only.
Riser gating -It is the gating system in which molten metal from the sprue enters a riser close to the mould cavity and then flows into the mould cavity. It is also the practice of running metal for the casting through the riser to help directional solidification.
Riser height – It is the distance from the top of the riser when liquid to the top of the riser neck. Riser height when sold is normally several centimeters less than when liquid because of contraction and loss of feed metal to the casting.
Riser neck – It is the connecting passage between the riser and casting. Normally only the height and width or diameter of the riser neck are reported, although the shape can be equally important.
Riser, open – It is the conventional form of riser usually located at the heaviest section of the casting and extending through the entire height of the cope.
Riser pad – It is an enlargement of the riser neck where it joins the casting. The purpose of the pad is to prevent the riser from breaking into the casting when it is struck or cut from the casting.
Riser, side – It is also called side head. It is a riser attached to the side of a casting.
Riser, top – It is also called top head. It is a riser attached to the top surface of a casting.
Riser tube – It is a vertical pipe or conduit which carries fluids or other materials, often connecting a lower point to a higher point, such as plumbing to higher floors in buildings. It can be part of an airlift reactor to mix fluids, a hot water pipe in boilers, or a vertical section connecting offshore pipelines to surface facilities.
Rise time – In urethane foam moulding, it is the time between the pouring of the urethane mix and the completion of foaming.
Rising stem – It is a valve stem which rises as the valve is opened.
Rising stem ball valve – It is a single-seated ball valve which is designed to seal by using the valve’s stem to mechanically wedge the valve’s ball into a stationary seat, affecting a bubble-tight seal. The valve’s stem operates through a guide sleeve assembly which guides the stem through a quarter turn of rotation as the stem is raised or lowered by a handwheel (or actuator). The mechanical action of the stem moves the ball away from the seat prior to the 90-degree rotation of the ball. The design provides lower operating torques and longer seat life while assuring bubble-tight shutoff.
Rising stem gate valve – It is designed so that the stem is raised out of the flow path when the valve is open. Rising stem gate valves come in two basic designs. One design has a stem which rises through the handwheel while others have a stem which is threaded to the bonnet.
Rising stem with inside screw – In this type of stem, the threaded part of the stem is inside the valve body, and the stem packing along the smooth section which is exposed to the atmosphere outside. In this case, the stem threads are in contact with the flow medium. When rotated, the stem and the hand-wheel rise together to open the valve.
Rising stem with outside screw and yoke – In this type of stem, the exterior of the stem is threaded, while the portion of the stem in the valve is smooth. The stem threads are isolated from the flow medium by the stem packing. Two different styles of these designs are available namely one with the hand-wheel attached to the stem, so they can rise together, and the other with a threaded sleeve which causes the stem to rise through the hand-wheel. This type of valve is a common design for 60 millimeters outside diameter pipe size and larger valves.
Risk – It is the probability of damage or injury i.e., the potential for harm to people, property, or the environment. It is the uncertainty which surrounds future events and outcomes. It is the expression of the likelihood and impact of an event with the potential to influence the achievement of an organization’s objectives. Risk is also the probability of a worker suffering an injury or health problem, or damage occurring to property or the environment as a result of exposure to or contact with a hazard. It can be expressed either as a frequency, such as the number of harmful effects in a certain time period, or as a probability, such as the probability of a harmful effect during or after exposure.
Risk analysis – It is the structured process of identifying, evaluating, and understanding potential negative events (risks) which can affect organization, project, or operation. It involves estimating the likelihood of these risks occurring and their potential consequences to determine the overall threat level. The goal is to gain insights into potential problems, their impact, and to develop strategies for reduction, prevention, and communication.
Risk assessment – It is the process of quantifying the frequency or probability of a harmful effect to individuals or populations (e.g., related to exposure or activities at work) and is one of the first steps in risk management. It is a systematic process of identifying, analyzing, and evaluating potential risks associated with a particular activity or project, ultimately aimed at understanding and mitigating those risks. It is a scientific evaluation of the probability of harm resulting from exposure to the potential risks. Under risk assessment included are (i) hazard identification taking recourse to hazard indices, inventory analysis, dam break probability, and natural hazard probability etc., (ii) maximum credible accident (MCA) analysis to identify potential hazardous scenarios, (iii) consequence analysis of failures and accidents resulting in fire, explosion, hazardous releases, and dam breaks etc., (iv) hazard and operability (HAZOP) studies, (v) assessment of risk on the basis of the above evaluations, and (vi) preparation of an onsite and offsite (project affected area) disaster management plan.
Risk assessment methodology – It is a systematic, structured approach used to identify, analyze, and evaluate potential risks which can impact an organization’s objectives, assets, or processes. It provides a blueprint for consistent risk evaluation by establishing how likelihood and impact are determined, allowing for the prioritization of risks and the informed development of strategies to mitigate or manage them effectively.
Risk assessment report – It is the report which contains the results of performing a risk assessment or it is the formal output from the process of assessing risk.
Risk-benefit analysis – It is a decision-making technique which uses a common value scale, normally monetary units, to balance the risk against benefit.
Risk identification – It is the first step in risk management, involving the process of discovering and documenting potential threats and opportunities which can impact an organization’s objectives or a project’s success. It is a continuous, iterative process which casts a wide net to uncover all possible events, conditions, or factors with a probability of occurring, rather than treating certain events as facts. The goal is to create a comprehensive list of risks with their characteristics, sources, and consequences, which is then used for further risk analysis and response planning to minimize negative impacts and maximize positive ones.
Risk management – It consists of all actions taken to achieve, maintain or improve work and working conditions so that harmful effects to individuals or populations related to exposure or activities at work are prevented. It is the process of (i) identifying, analyzing, assessing, and evaluating risks, (ii) assigning ownership, (iii) taking actions to mitigate or anticipate them, and (iv) monitoring and reviewing progress.
Risk mapping – It is the process of identifying high-risk areas is known as risk mapping. This is done by correlating a hazard, such as an earthquake, to the terrain and to the probability that such an event occurs. The results of these analyses are normally presented in the form of risk maps, which show the type and degree of hazard represented by a particular natural phenomenon at a given geographic location. Risk mapping is normally the first step in vulnerability reduction.
Risk mitigation – It is the process of reducing the impact or likelihood of potential threats to an organization, project, or operation by identifying risks, assessing their potential consequences, and then implementing strategies to manage, minimize, or eliminate them, ensuring operational continuity and the protection of assets.
Risk reduction measure – It is an action or strategy taken to lower the likelihood or severity of a hazard or adverse event, encompassing both engineered solutions like structural changes and non-engineered approaches such as administrative programmes and improved practices. These measures are designed to prevent accidents and their potential consequences by reducing vulnerabilities and improving safety in systems, structures, and processes, frequently following a hierarchy of controls.
Risk tolerance – It is the maximum level of risk which the organization is willing to accept in a process or activity to achieve its benefits, essentially determining the boundaries of acceptable risk-taking. It is influenced by the perceived risk against actual risk and is a key factor in decision-making, helping to balance strategic goals with safety objectives and guiding the implementation of risk management strategies within acceptable limits.
Risk transfer – It is the process of formally or informally shifting the financial consequences of particular risks from one party to another whereby an organization gets resources from the other party after a disaster occurs, in exchange for ongoing or compensatory financial benefits provided to that other party is known as risk transfer. Insurance is a well-known form of risk transfer, where coverage of a risk is obtained from an insurer in exchange for ongoing premiums paid to the insurer. Risk transfer can occur informally or formally. During formal risk transfer, governments, insurers, multi-lateral banks and other large risk-bearing entities establish mechanisms help cope with losses in major events. Such mechanisms include insurance and re-insurance contracts, catastrophe bonds, contingent credit facilities and reserve funds, where the costs are covered by premiums, investor contributions, interest rates and past savings respectively.
River intake – It is the structure or system used to withdraw water from a river, which can be located onshore or offshore, and is designed to convey raw water for different uses, including industrial use. It typically involves pumps and can be constructed with piles to support the intake line and manage water quality by reducing turbidity.
River pattern – It is a term used in fractography to describe a characteristic pattern of cleavage steps running parallel to the local direction of crack propagation on the fracture surfaces of grains which have separated by cleavage. It is a microscale characteristic pattern of cleavage crack propagation on closely spaced parallel planes connected by a thin ligament. Cracking on the connecting ligament can be ductile or brittle. Crack coalescence occurs as crack propagation occurs on the multiple planes, so that the microscale direction of crack propagation can be identified (i.e., ‘down river’).
Rivet – It is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylindrical shaft with a head on one end.
Riveting – It is the joining of two or more members of a structure by means of metal rivets, the unheaded end being upset after the rivet is in place.
Riveting brass – It is the brass which is formulated to be most suitable for riveting.
Riveting machines – These are mechanical devices used to join materials through self-piercing riveting, which can operate in several forms such as portable, robot-mounted, and multi-head configurations. They facilitate a quick, clean, and automated joining process with minimal energy needs and no fume emissions.
RLC circuit – It is a circuit which has only resistors, inductors, and capacitors in it.
Road network – It is a system of roads and points for a production plant and connect different plant facilities and buildings. A road network provides approaches to different production units and buildings. It greatly affects in-plant traffic and movement of man and materials. Road network is highly dependent on the plant general layout and can become very complex.
Road transportation – It is the movement of materials using vehicles on a network of roads. This involves the design, construction, maintenance, and operation of roads and related infrastructure, as well as traffic management systems, for ensuring safe, efficient, and sustainable transport. Key considerations for transportation engineers include road design (lanes, intersections, highways), pavement technology, traffic flow, and the integration of road networks with other transport modes.
Roasting – It is a process of heating a sulphide ore to a high temperature in the presence of air. It is a step in the processing of certain ores. More specifically, roasting is frequently a metallurgical process involving gas–solid reactions at high temperatures with the goal of purifying the metal component(s). Frequently before roasting, the ore has already been partially purified, e.g., by froth flotation. The concentrate is mixed with other materials to facilitate the process. The technology is useful in making certain ores usable but it can also be a serious source of air pollution. The roasting can include oxidation, reduction, chlorination, sulphation, and pyro-hydrolysis. In roasting, the ore or ore concentrate is treated with very hot air. This process is normally applied to sulphide minerals. During roasting, the sulphide is converted to an oxide, and sulphur is released as sulphur di-oxide, a gas. Roasting causes some chemical change which facilitate smelting.
Robber – It is an extra cathode or cathode extension which reduces the current density on what is otherwise a high-current-density area on work being electroplated.
Robotic arm – It is a programmable mechanical manipulator consisting of linked segments and joints, to perform automated tasks. These systems feature multiple degrees of freedom (DOF) from motorized joints, allowing for precision and controlled movements. These arms are integral to automation in manufacturing, and other fields, equipped with a robotic gripper to interact with the environment.
Robotic gripper – It is designed to grasp, hold, manipulate, and release work-pieces or objects. Mounted on a robotic arm or manipulator, grippers use electric, pneumatic, hydraulic, or other power sources to open and close, enabling robotic arm to perform tasks such as pick-and-place operations, assembly, and machine tending.
Robotics – It is the interdisciplinary study and practice of the design, construction, operation, and use of robots. Within mechanical engineering, robotics is the design and construction of the physical structures of robots, while in computer science, robotics focuses on robotic automation algorithms. Other disciplines contributing to robotics include electrical, control, software, information, electronic, tele-communication, computer, mechatronic, and materials engineering. The goal of most robotics is to design machines which can help and assist humans. Several robots are built to do jobs which are hazardous to people.
Robust – It describes a system, product, or process which maintains consistent performance despite external disturbances or internal variations. A robust design is insensitive to noise, such as manufacturing tolerances or changing environmental conditions, ensuring that its intended function is not compromised. This is achieved by minimizing the impact of variation, frequently through statistical methods, for ensuring consistent output and reliability in real-world scenarios.
Robust control – It is a static control algorithm which can produce acceptable performance over an anticipated useful range of process disturbances.
Robust control system – It is a control system designed to maintain its intended stability and performance despite uncertainties and disturbances in the system’s parameters or environment. Instead of relying on a perfect model, robust control accounts for imperfect models, external noise, and plant parameter variations by ensuring the system meets its performance specifications across a range of possible conditions. Key objectives include achieving low system sensitivity, remaining stable, and meeting performance requirements even when faced with a set of potential changes in the system.
Robust design – It is an integrated system of tools and techniques which are aimed at reducing product or process performance variability while simultaneously guiding that performance toward an optimal setting. Robustness optimization is chiefly done for design concepts that are new so that the best values of the critical functional parameters are unknown. Robust design follows the methods first proposed by Genichi Taguchi.
Robustness – It means of performance of a system that is always acceptably close to the ideal function of the system. It refers to how consistently a component or product performs under variable conditions in its environment and as it wears during its lifetime.
Robust optimal control (ROC) – I(t is a control design methodology which seeks to find a control strategy that performs optimally not only under ideal conditions but also under a range of possible uncertainties or disturbances. It achieves this by optimizing performance for a worst-case scenario, ensuring the system maintains stability and acceptable performance despite variations in its dynamics, which is crucial for safety-critical applications and systems where reliability is paramount.
Robust stability – It is the property of a system which allows it to maintain stable operation and effective performance despite uncertainties or perturbations in its parameters, structure, or environment. It means the system’s stability is not fragile and can withstand variations from its nominal or ideal conditions. For example, a robustly stable control system continues to function correctly even if there are slight inaccuracies in the modeled plant dynamics or small external disturbances.
Rochelle copper – It is a copper electrodeposit obtained from copper cyanide plating solution to which Rochelle salt (sodium potassium tartrate) has been added for grain refinement, better anode corrosion, and cathode efficiency. It is the solution from which a Rochelle copper electro-deposit is obtained.
Rochelle salt – It is also known as sodium potassium tartrate or Seignette salt. It is a double salt of tartaric acid with the chemical formula KNaC4H4O6·4H2O, characterized by its piezoelectric properties and use in sensitive acoustic and vibrational devices.
Rock – It consists of a natural combination of minerals. It is part of the earth’s crust.
Rock anisotropy – It is the variation in material properties, such as Young’s modulus and fracture toughness, in different directions within a rock, which affects the propagation patterns of hydraulic fractures and the resultant stress shadows during fracturing processes.
Rock bolt – It is a long steel rod or bar which is anchored into a drilled hole in a rock mass to provide support and stabilize it. It functions by transferring loads from unstable outer rock layers to more stable, deeper interior sections, hence strengthening the rock mass. Rock bolts are a fundamental ground reinforcement technique used in mining, tunneling, and civil engineering projects like roadcuts and slope stabilization to prevent collapses and ensure structural integrity.
Rock-bolting – It is the act of supporting openings in rock with steel bolts anchored in holes drilled especially for this purpose.
Rock box – It is a specially designed shelf or ledge at the bottom of a transfer chute on a conveyor belt system. It is mainly used to protect the chute from wear by absorbing the impact of falling ore. It captures incoming material, collects rock and dust on its surface, and directs the material flow onto the lower conveyor belt to prevent damage and guide the material to the centre of the belt.
Rock-burst – It is a violent release of energy resulting in the sudden failure of walls or pillars in a mine, caused by the weight or pressure of the surrounding rocks.
Rock candy fracture – It is a macro-scale and micro-scale fracture appearance which shows separated-grain facets. Very frequently it is used to describe the macroscale appearance of an intergranular fracture in a large-grained metal, although the term is also used to describe the microscale appearance of facets observed from an intergranular fracture path with equiaxed grains.
Rock drill – It is a percussive or rotary tool, powered by air, hydraulics, or electricity, used to bore holes into hard materials like rock and concrete for applications in mining, civil engineering, and quarrying. These tools utilize a drill bit, typically tipped with tungsten carbide, to penetrate the material, with their design varying from small handheld devices to large, machine-mounted systems depending on the specific job requirements.
Rock drilling – It is the controlled process of creating holes or boreholes in rock formations using specialized tools and machinery to enable various operations like mining, construction, tunneling, or geological exploration. It involves the selection and application of appropriate drilling methods, such as percussive or rotary, along with equipment like drill bits and drilling fluids, all tailored to the specific rock type and project requirements.
Rocket – It is a vehicle which uses jet propulsion to accelerate without using any surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely from propellant carried within the vehicle. Hence a rocket can fly in the vacuum of space. Rockets work more efficiently in a vacuum and incur a loss of thrust due to the opposing pressure of the atmosphere.
Rock factor – It is the number of cubic meters of a particular rock type required to make up one ton of the material. One ton of a highly siliceous ore can occupy 0.4 cubic meters, while a ton of dense sulphide ore may occupy only 0.25 cubic meters.
Rock formation – It refers to an aggregate of mineral grains or materials, frequently cemented together, which shows specific properties like strength, deformability, and porosity which determine its behaviour under stress and its suitability for engineering applications like construction and resource extraction. While geology mainly defines a rock formation by its stratigraphic position, petrology, and surface features resulting from erosion, engineering focuses on its intrinsic physical properties and how it exists in situ (in its natural place) as a component of the earth’s crust.
Rock fracture – It is the creation of a break or discontinuity within a rock mass, where the rock’s integrity is lost because of the applied stress. These fractures form as cracks which initiate and extend on a micro or macro scale, ultimately leading to the separation of the rock body into two or more pieces. Key to understanding rock fractures are their types (e.g., faults with displacement and joints without), the stresses which cause them (tensile, shear, or combined), and their impact on fluid migration and overall rock mass stability for engineering projects.
Rocking curve – It is a method for determining the degree of imperfection in a crystal by using monochromatic, collimated X-rays reflecting off a ‘perfect’ crystal to probe a second test crystal. A rocking curve is obtained by monitoring the x-ray intensity diffracted by the test crystal as it is slowly rocked, or rotated, through the Bragg angle for the reflecting planes.
Rocking-die forging – It is also known as orbital or rotary forging. It is a forging process where one die orbits or rocks relative to the other, gradually deforming the work-piece into its final shape. It is frequently used for symmetrical parts like gears and hubs.
Rocking shear – It is a type of guillotine shear which utilizes a curved blade to shear sheet metal progressively from side to side by a rocker motion.
Rock mechanics – It is the study of the mechanical properties of rocks, which includes stress conditions around mine openings and the ability of rocks and underground structures to withstand these stresses.
Rock strength – It is a rock’s capacity to resist failure when subjected to applied stress. It is a fundamental property which determines how a rock behaves under load and is classified into specific types, including compressive strength, the resistance to being crushed; tensile strength, the resistance to being pulled apart; and shear strength, the resistance to sliding or tearing.
Rock structure – It is the arrangement of solid grains, which vary in size, shape, and orientation, that are in contact and may be cemented together, forming a porous medium with spaces that can contain fluids such as oil, water, and gases. The interlocking of grains and the degree of cementation considerably influence the rock’s strength.
Rock weathering – It describes the breaking down or dissolving of rocks and minerals on the surface of earth. Water, ice, acids, salts, plants, animals and changes in temperature are all agents of weathering. Once a rock has been broken down, a process called erosion transport the bits of rock and mineral away. No rock on earth is hard enough to resist the forces of weathering and erosion. Weathering wears away exposed surfaces over time. The length of exposure frequently contributes to how vulnerable a rock is to weathering. As it smooths rough, sharp rock surfaces, weathering is frequently the first step in the production of soils. Tiny bits of weathered minerals mix with plants, animal remains, fungi, bacteria, and other organisms. A single type of weathered rock often produces infertile soil, while weathered materials from a collection of rocks is richer in mineral diversity and contributes to more fertile soil. Soils types associated with a mixture of weathered rock include glacial till, loess and alluvial sediments.
Rockwell hardness number – It is a number which is derived from the net increase in the depth of impression as the load on an indenter is increased from a fixed minor load to a major load and then returned to the minor load. Different scales of Rockwell hardness numbers have been developed based on the hardness of the materials to be evaluated. The scales are designated by alphabetic suffixes to the hardness designation. As an example, 65 HRC represents the Rockwell hardness number of 65 on the Rockwell C scale.
Rockwell hardness scales – There are several Rockwell scales other than the B and C scales, which are known as the common scales. The other scales also use a letter for the scale symbol prefix, and many use a different sized steel ball indenter. A properly used Rockwell designation has the hardness number followed by ‘HR’ (Hardness Rockwell), which is followed by another letter which indicates the specific Rockwell scale. For example, 60 HRB indicates that the sample has a hardness reading of 60 on the B scale. The standardized a set of scales (ranges) for Rockwell hardness testing under use is normally designated by a letter. This set is (i) A scale which is used for cemented carbides, thin steel, and shallow case-hardened steel, (ii) B scale which is used for copper alloys, soft steels, aluminum alloys, and malleable iron, etc., (iii) C scale which is used for steel, hard cast irons, pearlitic malleable iron, titanium, deep case hardened steel and other materials harder than the hardness value of B100, (iv) D scale which is used for thin steel, medium case-hardened steel, and pearlitic malleable cast iron, (v) E scale which is used for cast iron, aluminum and magnesium alloys, and bearing metals, (vi) F scale which is used for annealed copper alloys and thin soft sheet metals, (vii) G scale which is used for phosphor bronze, beryllium copper, and malleable irons, (viii) H scale which is used for aluminum, zinc, and lead, and (ix) K, L, M, P, R, S, and V scales which are used for bearing metals and other very soft or thin materials, including plastics.
Rockwell hardness test – It is an indentation hardness test using a calibrated machine which utilizes the depth of indentation, under constant load, as a measure of hardness. It is a hardness measurement method which is based on the net increase in depth of impression as a load is applied. Hardness numbers have no units and are normally given in some scales such as the A, B, C, R, L, M, E and K scales. The higher the number in the scales means the harder is the material. Rockwell hardness test is the most used and versatile of the hardness tests. In the Rockwell method of hardness testing, the depth of penetration of an indenter under certain arbitrary test conditions is determined. It uses either a spherical diamond tipped cone called ‘Brale’ which is of 120-degree angle and 0.2 millimeters tip radius or a steel ball with 1.6 millimeters or 3.2-millimeters diameter ball as the indenter. The type of indenter and the test load determine the hardness scale (A, B, C, etc.). A minor load of 10 kilograms is first applied, which causes an initial penetration and holds the indenter in place. Then, the dial is set to zero and the major load is applied. Upon removal of the major load, the depth reading is taken while the minor load is still on. The hardness number can then be read directly from the scale.
Rockwell hardness testing machine – It is used to measure the hardness of metal. It measures resistance to penetration like the Brinell test, but in this case, the depth of the impression is measured rather than the diametric area. With the Rockwell testing machine, the hardness is indicated directly on the scale attached to the machine. This dial like scale is really a depth gauge, graduated in special units. The Rockwell testing machine uses two loads with one is applied directly after the other. The first load (known as the minor load) of 10 kilograms is applied to the sample to help seat the indenter and remove the effects, in the test, of any surface irregularities. The purpose of the minor load is to create a uniformly shaped surface for the application of the major load. The difference in the depth of the indentation between the minor and major loads provides the Rockwell hardness number.
Rockwell superficial hardness number – Like the Rockwell hardness number, the superficial Rockwell number is expressed by the symbol HR followed by a scale designation. For example, 81 HR30N represents the Rockwell superficial hardness number of 81 on the Rockwell 30N scale.
Rockwell superficial hardness test – It is the same test as used to determine the Rockwell hardness number except that smaller minor and major loads are used. The working of this machine is similar to the standard Rockwell testing machine, but it is used to test thin strip, or lightly carburized surfaces, small parts or parts that might collapse under the conditions of the regular test. In Rockwell testing, the minor load is 10 kilograms force, and the major load is 60 kilograms force, 100 kilograms force, or 150 kilograms force. In superficial Rockwell testing, the minor load is 3 kilograms force, and major loads are 15 kilograms force, 30 kilograms force, or 45 kilograms force. In both tests, the indenter can be either a diamond cone or a steel ball, depending principally on the characteristics of the material being tested. Using the 1.6 millimeters diameter, steel ball indenter, a ‘T’ is added (meaning thin sheet testing) to the superficial hardness designation. For example, a superficial Rockwell hardness is 15T-25, which indicates the superficial hardness as 25, with a load of 15 kg using the steel ball. If the 120-degree diamond cone is used instead, then ‘T’ is replaced with ‘N’.
Rod – It is round, thin semi-finished steel length which is rolled from a billet and coiled for further processing. Rod is normally drawn into wire products or used to make bolts and nails. Rod is the hot rolled finished product having a nominal size normally 5 millimeters or higher and hot wound into irregular coils. The cross-section of the rod can also be besides circular, oval, square, rectangular, hexagonal, octagonal, half-round or other shape. Rod has a smooth surface and is normally intended for subsequent conversion. Rod used for wire-drawing purposes in coil form is normally termed as wire rod.
Rod, alclad – It is the rod having on its surface a metallurgically bonded aluminum or aluminum alloy coating which is anodic to the core alloy to which it is bonded, hence electrolytically protecting the core alloy against corrosion.
Rod bundle – it refers to a configuration where multiple cylindrical rods are grouped together, frequently arranged in a specific lattice like a triangle or square, and contained within a duct or housing. These bundles are critical in different applications, most notably in nuclear reactors for fuel assemblies, but also in heat exchangers, as the arrangement considerably influences fluid flow and heat transfer characteristics within the bundle.
Rod, cold-finished – It is the rod which is brought to final dimensions by cold working to get improved surface finish and dimensional tolerances.
Rod, cold-finished extruded – It is the rod which is produced by cold working extruded rod.
Rod, cold-finished rolled – It is the rod produced by cold working rolled rod.
Rod, cold-heading – It is the rod of a quality suitable for use in the manufacture of cold-headed products such as rivets and bolts.
Rodding – It is the reinforcing of the sand in a core with metal rods or shapes to strengthen parts of the core.
Rod drawing – It is a metalworking process where a rod is pulled through a die to reduce its cross-sectional area and increase its length, resulting in a long, thin product like rods or wires. Rod drawing involves applying both tensile and compressive forces to a rod as it is pulled through a die with a smaller opening than the rod’s initial diameter. The main objective is to produce long, thin, and frequently precise rods or wires with a reduced cross-sectional area.
Rod end bearing – It is the connection frequently used between actuator stem and actuator lever to facilitate conversion of linear actuator thrust to rotary force (torque) with minimum of lost motion. Use of a standard reciprocating actuator on a rotary valve body normally needs linkage with two rod end bearings. However, selection of an actuator specifically designed for rotary valve service needs only one such bearing and hence reduces lost motion.
Rod expansion thermometer – It is also known as a solid-expansion thermometer. It measures temperature by detecting the change in length of a metal rod or the deflection of a bimetallic strip as it expands or contracts with temperature changes.
Rod, extruded – It is the rod produced by hot extruding.
Rod heading machines – These machines are open die heading machines having either single or double stroke. They are used for extremely long work-piece (8 times to 160 times work piece diameter). The work-piece is cut to length in a separate operation in another machine and fed manually or automatically into the rod heading machine.
Rod mill – It is a hot rolling mill for rolling rod.
Rod mill, grinding – It is a mill for fine grinding, somewhat similar to a ball mill, but employing long steel rods instead of balls to effect grinding. Rod mills are only suited for those kinds of ores which are of a fairly coarse nature but once they are broken, disintegrate readily into small size. Typically, rod mills mill can deliver a product with a fineness of less than 0.1 millimeters. Testing of material is needed before hand to determine the suitability of the ore for processing in an autogenous mill. Rod mill is a tumbling mill which is having a large percentage of its volume (30 % to 40 %) loaded with steel rods. The rods are placed axially in the mill and are loose and free to move within the mill. The internal lining of the drum has a series of lifters which raise the rods and drop them at a predetermined point. The liners prevent long and heavy rods to slide on the cylinder lining and help them to lift up. Because of the high kinetic energy of a dropping rod, it is important to pay attention to protecting the cylinder when choosing a liner for the mill.
Rod, rivet – It is the rod of a quality suitable for use in the manufacture of rivets.
Rod, rolled – It is the rod produced by hot rolling.
Rod section – It refers to the shape and size of a metal rod during the rolling process, which can include several geometries such as circular, oval, square, rectangular, hexagonal, octagonal, half-round or other shape. These cross-sectional shapes are important for achieving the desired dimensions and ensuring proper roll entry during production.
Roentgen – It is a legacy unit of measurement for the exposure of X-rays and gamma rays, and is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air (statcoulomb per kilogram).
Roentgen equivalent man – It is a standard unit of radiation dose. It measures the effects of ionizing radiation on humans. The dose equivalent in Roentgen equivalent man is equal to the absorbed dose in rads multiplied by the quality factor of the type of radiation.
Rogowski coil – It is a current sensing coil which produces a voltage proportional to the rate of change of current. By integration, this can be turned into a measure of current.
Roll balancing system – It aims to ensure the precise alignment of the centre of gravity of the rolls with their axis of rotation, minimizing vibrations and ensuring uniform metal deformation during the rolling process.
Roll bearing – It refers to rolling-element bearings (like cylindrical roller bearings or spherical roller bearings) used to support the rotating rolls and minimize friction, allowing for smooth and efficient metal deformation during the rolling process. Roll bearings are needed to withstand heavy loads and high-speed rotations as well as severe operating environments. These bearings, especially which are used in the process of hot rolling, are frequently used under severe conditions, high temperatures with possibilities of intrusion of foreign materials. These bearings are to endure these severe conditions.
Roll bending – It consists of curving sheets, bars, and sections by means of rolls. Roll bending is a process which allows creation of intricate, curved shapes out of metal sheets, bars, and tubes. Roll bending, also known as plate rolling or angle bending. It is a metalworking process which uses a series of rollers to bend a metal piece into a specific curve or radius. The metal is forced through the rollers, progressively applying pressure to shape the material into the desired curvature. This process is normally used for manufacturing pipes, tanks, and other cylindrical or conical shapes.
Roll bite – It refers to the pinch point or contact area between the upper and lower rolls where the metal stock is drawn into and deformed. It is the region where the rotating rolls grip and deform the metal, reducing its thickness and shaping it. Roll bite condition is the condition which determines the material to be rolled to enter the throat of the roll.
Roll camber – It refers to the intentional curvature (or crown) introduced into the rolls, typically with a larger diameter in the centre than at the edges, to counteract bending and ensure a consistent thickness of the rolled product. Roll camber can be varied by (i) bending the work rolls by applying external force, (ii) shifting of work rolls laterally with respect to centerline of the strip, (iii) using shaped rolls (rolls with profiles), and (iv) rotation of the axis of the work roll with respect to axis of backup-roll in horizontal plane (results in deflection of work roll ends, producing camber).
Roll changing – It means rapidly changing top and bottom working rolls and top and bottom backup rolls in case of a four high rolling mill. Roll changing is normally done with the use of an overhead crane and a unit designed to attach to the neck of the roll to be removed from or inserted into the mill.
Roll changing device – It is a special device which is designed to attach to the neck of the roll for the removal or insertion of the rolls into the rolling mill stands.
Roll chatter – It consists of numerous intermittent lines or grooves which are normally full width and perpendicular to the rolling or extrusion direction.
Roll coating – It is a banded condition caused by non-uniform adherence of roll coating to a work roll. It can be created during hot and / or cold rolling. If generated in the hot rolling process, it also is called hot mill pickup.
Roll chock – It is a component which supports the work-rolls and back-up rolls. while they are being rolled. Roll chocks are critical components of rolling mills and play a significant role in the success of the mill operation. The main function of roll chock in rolling mill is to house and accommodate the roll neck bearings. Roll neck bearings serve for accurate mounting of roll necks, in both horizontal and vertical plane. Roll chocks are designed to fit into the window of the housing in such a way that they are important component in a rolling mill for maintaining accurate positioning of the rolls. During rolling, the load on the rolls gets transferred to the roll neck bearings and their assembly (chocks). The important features of roll chocks are that they have special holes (bores) for slider bearings, antifriction bearings, or oil film bearings. They have side support planes. For increasing the wear resistance and to prolong chocks work life, these planes are equipped with lining plates having different hardness of surfaces. The surface of the roll chock in contact with the bearing needs precision, and accuracy, as well as close and smooth finish.
Roll compacting – It is the progressive compacting of metal powders by use of a rolling mill.
Roll configuration – It refers to the arrangement and number of rolls used to shape metal, including two-high, three-high, four-high, and cluster mills, each suited for different applications and desired outcomes.
Roll crusher – It is a size reduction machine with two opposite-rotating cylindrical rolls which crush material by compression as it passes through the gap between them. It works by gripping and nipping the material, fracturing it into smaller pieces. Roll crushers are designed to process soft to moderately hard brittle materials such as coal, clay, and certain ores, and they are known for producing a relatively fine product with minimal dust generation.
Roll eccentricity compensation – Roll eccentricity is a periodic disturbance caused by a structure of back-up rolls in rolling mills, and it affects product thickness accuracy. It cannot be measured directly by sensors, so it is to be identified by measured thickness or measured roll force. When there is a large difference of diameters between top and bottom back up roll, the performance of roll eccentricity control using feedback signals of roll force or thickness has not been so good. Also, it has been difficult for the control to be applied from the most head end since it is necessary to identify the roll eccentricity during rolling. Roll eccentricity compensation control identifies top and bottom roll eccentricity respectively from one signal of roll force and it starts the control from head end.
Rolled compact – It is a compact which is made by passing metal powder between rollers so as to form a relatively long, sheet-like compact.
Rolled finished products – These are the products which have been manufactured normally by rolling and which are normally not further hot worked in the steel plant. The cross-section is uniform over the whole length. It is normally defined by a standard, which fixes the normal size ranges and the tolerances on shape and dimension. The surface is normally smooth, but reinforcing bars or floor plates, for example, can have a regularly raised or indented pattern.
Rolled glass – It is a translucent glass with 50 % to 80 % light transmission, depending on its thickness and type of surface. It is used where transparency of the glass sheet is not important or not desired. To produce rolled glass, molten glass pours from the melting tank over a refractory barrier (the weir) and onto the machine slab where it flows under a refractory gate (the twee), which regulates the volume of glass, and then between two water-cooled rollers. The distance between the rollers determines the thickness of the glass.
Rolled-in metal – It is an extraneous chip or particle of metal rolled into the surface of the product.
Rolled in scale – Scale is the oxide layer of varying thickness and colouring on the surface of the wire rod which can cling loosely or adhere firmly. Rolled in scale forms an irregular impression in the surface of the wire rod and is caused by incomplete descaling after the heating operation. It can cause a pitted surface on the wire rod. The defect results in wire rod surface irregularly. It can be detected visually. By rubbing with an abrasive tool to remove uniform depth scale, the underneath surface can be revealed. The occurrence of rolled in scale is most dependent on the adherence and not the quantity of primary scale produced. Scale adherence is a function of steel composition, furnace heating practices, and prior surface condition of the incoming billets. Modifications sometimes are made to roll pass designs to promote more complete scale breaking and removal. Slab or box passes are the best roughing passes for scale removal.
Rolled-in scratch – It is the scratch which is subsequently rolled. It then appears as a grayish white ladder (distinct transverse lines within the longitudinal indentation).
Rolled metal, rolled steel – Rolled metal / rolled steel refers to a metal / steel which has been shaped and its thickness reduced by passing it through one or more pairs of rollers, a process known as ‘rolling’. This process can be done hot or cold, and is used to create sheets, plates, rods, or other desired shapes and thicknesses.
Rolled-over edge – It is surface condition remaining after portions of a side of an as-cast rolling ingot deforms enough during hot rolling to become top and / or bottom surface(s) of the rolled product at an edge.
Rolled ring – It is a cylindrical product of relatively short height, circumferentially rolled from a hollow section.
Rolled steel – It is the steel which has been shaped and refined by passing it through a series of heavy rollers, much like rolling out dough with a pin. This process, called rolling, alters the steel’s shape, thickness, and mechanical properties. There are two main types namely (i) hot rolled steel, formed at very high temperatures and typically having a rougher surface and rounded edges, and (ii) cold rolled steel, which is further processed at room temperature for a smoother finish, higher strength, and more precise dimensions.
Rolled steel joist (RSJ) – It is a common type of beam used for structural steelwork. It is also known as an ‘I-beam’. A rolled steel joist is abeam with an ‘I’ or ‘H’-shaped cross-section. It comes in a variety of standard sizes. It is a very efficient form for carrying bending and shear loads in the plane of the web (the vertical element). It is normally made from mild steel but can also be formed from aluminum or other materials. It is formed by hot rolling, cold rolling, or by extrusion.
Rolled steel section – It is a standardized structural steel shape, such as an I-beam, channel, or angle, manufactured by passing hot or cold steel through rollers to form the desired cross-sectional profile. These sections are designed with pre-determined dimensions and properties, documented in design codes, which allows for efficient and reliable use in construction for beams, columns, and other structural components.
Rolled threads – These threads are produced through rolling or sliding dies. Rolled threads (as opposed to threads cut on a lathe, with a cutting die or tap) produce superior surface finish (hence lower stress risers) and improved material properties from cold working the material, resulting in much higher fatigue resistance. Rolled threads increase thread strength by a minimum of 30 % over well-cut threads.
Roll elastic deformation – It refers to the temporary change in shape of the rolls (work rolls and back-up rolls) due to the pressure exerted by the metal being rolled, with the rolls returning to their original shape when the force is removed.
Roller air analyzer – It is an air-elutriation apparatus suitable for the particle size determination of metal powders, especially in sub-sieve range. It consists, essentially, of a device by which powder particles are blown into a settling chamber through which dried and metered air moves at a uniform measurable velocity. Means are provided for collecting the particles carried out of the settling chamber and for removing and re- circulating lodged particles.
Roller bearings – These bearings are very frequently used when maximum load capacity is needed in a minimum of space. They are cylindrical and needle roller bearings where the rolling function is provided by a cylinder of some kind. Roller bearings are low friction and are designed to carry medium to heavy radial loads. In this type of bearing, the primary roller is a cylinder, which means the load is distributed over a larger area, enabling the bearing to handle larger amounts of weight. This structure, however, means the bearing can handle primarily radial loads, but is not suited to thrust loads. For applications where space is an issue, a needle bearing is normally used. Needle bearings work with small diameter cylinders, so they are easier to fit in smaller applications. These bearings are commonly found in general machine applications including gearboxes and transmissions, machine tool and construction equipment.
Roller chain – It is the type of chain drive normally used for transmission of mechanical power on several kinds of industrial machinery, such as conveyors, wire-drawing and tube-drawing machines. It consists of a series of short cylindrical rollers held together by side links. It is driven by a toothed wheel called a sprocket. It is a simple, reliable, and efficient means of power transmission. The major purpose of rollers is to reduce friction, but the rollers in chains have two separate functions, normally being provided by the same roller. These functions are (i) to engage the sprocket teeth and thus transfer any sliding action to the internal members of the chain, which are designed for that purpose, and (ii) to serve as a guide or to support a chain and material carried on it on tracks or ways, as is characteristic of conveyors and some bucket elevators. Rollers in drive chains are normally smaller in diameter than the height of the link plates of the chain. Hence, the link plates serve as guides when the chain engages the sprockets, and can also do so when the chain is riding on guides, as in a bucket elevator. Rollers on conveyor chains normally have diameters considerably larger than the widths of their adjacent sidebars. This is done for two reasons namely (i) the large rollers, called carrier rollers, carry the sidebars well above the conveyor tracks and thus prevent friction, and (ii) larger rollers have a definite mechanical advantage over smaller rollers relative to rotational friction, and thus help reduce chain pull.
Roller-chain flexible coupling – It utilizes two sprocket-like members, or hubs, that are mounted on the driver and the equipment shafts. They are connected by a section of roller chain. This type of coupling is typically applied in low-speed services.
Roller-coater –This method consists of a small movable tank and pumping unit, which feed a wiping head or roller with lubricant. The thickness and the amount of lubricant can be controlled, and the excess flows back to the reservoir. When lubricating pre-coated or polished materials with a roller-coater, it is advisable to use polyurethane or neoprene rolls to make sure the working surfaces are not scratched or marked. Steel rolls can sometimes cause problems on coated surfaces. In many cases, roller-coaters by themselves do not produce enough lubrication film to flush out particles generated by aluminum, galvanized, and hot roll. Sometimes, a sprayer installed in the critical areas of metal working where there is a possibility of buildup to occur, can flush out unnecessary particles. Another issue which can happen when applying lubricant (especially on wide strip) is a result of material which has a ‘crown’. In such a case, the roller can only lubricate the high spots, leaving the outside edges without lubricant. A similar issue can occur on wavy strip. A soft roller can help in adjusting itself to this crown or wavy condition.
Roller cone bits (RCBs) – These are drilling tools characterized by chisel-like teeth, frequently made of hardened carbide or diamond surfaces, designed to create holes in hard formations using fluid or air. They are noted for their endurance and improved directional performance in steerable assemblies.
Roller conveyor systems – These are used as mechanical handling equipment which moves materials from one location to another. These systems provide quick and efficient transportation for a wide variety of materials, which make them very popular for the material handling in the industries. A roller conveyor supports unit type of load on a series of rollers, mounted on bearings, resting at fixed spacings on two side frames which are fixed to stands or trestles placed on floor at certain intervals. A roller conveyor essentially coveys unit loads with at least one rigid, near flat surface to touch and maintain stable equilibrium on the rollers, like slabs, billets, plates, rolled stock, pipes, logs, boxes, crates, and moulding boxes etc. The spacing of rollers depend on the size of the unit loads to be carried, such that the load is carried at least by two rollers at any point of time. Roller conveyors are used for conveying almost any unit load with rigid riding surface which can move on two or more rollers. These are particularly used between machines, buildings, in warehousing as storage racks, docks, foundries, rolling mills, manufacturing, assembly and packaging industry. They are also used for storage between work-stations and as segment of composite handling system. However, the limitations of rollers conveyors are that they can be best used for objects with rigid flat surfaces, and for movement to relatively short distances. They need side guards to retain the loads from falling off. Gravity roller conveyors have the risk of accelerating loads. Roller conveyors are classified into two groups according to the principle of conveying action. These are (i) not powered or idle roller conveyor, and (ii) powered or live roller conveyor.
Roller crusher – It is a crusher which breaks material by squeezing it between two revolving metal cylinders, with axes parallel to each other and separated by a space equal to the desired maximum size of the finished product. It consists essentially of two opposite directions driven cylinders that are mounted on horizontal shafts. The other shaft is mounted permanently in the frame and is leaning on robust springs. The gap between cylinders can be adjusted, so the size of crushed product is easily adjustable. Usually both cylinders are covered with manganese steel liners. Crushing ratio is normally lower than in other crushers. Roll crusher is suitable for fine crushing. The roll crusher uses compression to crush materials. Reduction ratio is 2 to 2.5 to 1. Roller crushers are not recommended for abrasive materials.
Roller guides – The design of roller guides is based on rolling frictions and hence these guides have a number of advantages over static guides whose design is based on sliding friction. Roller guides ensure faster and accurate adjustment of the guiding elements when compared with the static guides. Since the contact of the rolling stock with the guide is carried through the rollers working on rolling friction, it becomes possible to considerably increase the wear resistance of the working elements (rollers) and to reduce the possibility of such rolling defects like scratches, laps, and score marks etc. The construction and assembly of the roller guides is carried out with sufficient strength to withstand the frequent hits from the rolling stock being rolled which is usually moving at a very high speed in the modern mills. The presence of safety components in the roller guide design make it possible to protect the costly parts, which are seldom replaced. This is especially necessary in the exit roller guide, where there is possibility of the end of the rolling stock jamming as it comes out of the work rolls. Roller guide design usually make is possible to withdraw jammed rolling stock quickly. In modern roller guides, drop forged roller holders in spring steel quality, are used which enables thicker front and tail ends to pass through the guide without disturbing the original setting of the roller guide.
Roller hearth furnace – It is a modification of the pusher-type continuous furnace which provides for rollers in the hearth or muffle of the furnace whereby friction is greatly reduced and lightweight trays can be used repeatedly without risk of unacceptable distortion and damage to the work.
Roller hearth reheating furnace – Roller hearth furnaces are used to advantage when heating very long billet, bloom or slabs in the situation where it is not practical for heating in a pusher or walking beam furnace. In the roller hearth furnace, the hearth consists of a set of water-cooled driven rollers on which the steel stock moves forward. The advantages of the roller hearth reheating furnaces are (i) it has ability to handle very long pieces, (ii) the zone control in this furnace is simpler when cross-firing is employed, (iii) material suffers little or no mechanical damage, (iv) skid marks are not there, and (iv) roller hearth furnace is self-emptying. The disadvantages of the roller hearth furnace include (i) high initial cost per unit of capacity, (ii) if the rollers are not properly insulated then there is increased heat loss due to the water cooling of the rollers, and (iii) roller hearth furnaces are narrower and longer than pusher type or walking beam furnaces of the same capacity.
Roller leveller – It is normally simply referred to as a leveller It is similar to a four-high flattener in that the design involves four-high small diameter work rolls. Unlike the four-high flattener, however, each work roll in the leveller is supported by a number of narrow backup rolls, instead of straight solid backup rolls. This arrangement allows small work rolls and a close work roll spacing in the leveller for more capability in shape correction. A series of backup rolls at the same transverse position for all work rolls under the same frame are called a flight, and they have a common support housing extending from the entry to the exit of the roller leveller. Each flight of backup rolls can be vertically adjusted, independently from other flights, by either a mechanical or a hydraulic mechanism. A deflection of work rolls in the leveller, hence, can be deliberately adjusted in a controlled manner. Roller levellers have normally seven to nineteen work rolls. Some levellers have the five-high or six- high backup design for high surface finish quality strip. The six-high levellers have two additional rows of straight solid intermediate rolls between work rolls and adjustable backup rolls, each at the top and bottom frames. This arrangement prevents marking on the top and bottom surfaces of the strip but limits the capability to correct poor shape since the adjustable roll flights act on the intermediate rolls. The five-high leveller has only one row of the intermediate rolls between work rolls and backup roll, normally in the lower frame, while its upper frame contains only work rolls and backup rolls as in four-high levellers. Hence, it gives better capability for shape correction than the six-high leveller, while preventing marking on one side of the strip surfaces. A roller leveller has a certain capability range in strip thickness for a given work roll diameter and roll spacing. Normally, the upper strip thickness limit is 3 times to 4 times that of the lower limit. Roller levellers have the ability to control the deflection of work rolls so that one portion of the material across the strip width can be subjected to more bending than another portion. The bending causes a tension in the material of the outer layers in the strip and compression in the material of the inner layers near the work roll. At a certain bending radius, the stress in the material at the outer-most layer exceeds the material yield strength and permanent plastic elongated deformation occurs.
Roller leveller breaks – These are obvious transverse breaks normally around 3 millimeters to 6 millimeters apart caused by the sheet metal fluting during roller levelling. These are not to be removed by stretching.
Roller leveller lines – These are lines on sheet or strip which are running transverse to the direction of roller levelling. These lines can be seen upon stoning or light sanding after levelling (but before drawing) and can normally be removed by moderate stretching. These are also known as leveller lines.
Roller levelling – It is also called tension levelling. It is the levelling by-passing flat sheet metal stock through a machine having a series of small-diameter staggered rolls that are adjusted to produce repeated reverse bending. It consists of flattening of sheet, strip or coil metal by passing it through a roll train staggered rolls. Levelling is achieved by precisely bending metal strip back and forth as it is passed through a series of small-diameter offset rolls. The material is normally also under tension loading.
Roller magnetic separator – It is an industrial equipment which uses a powerful magnetic roller, enclosed by a conveyor belt, to separate ferrous and para-magnetic materials from a non-magnetic stream of dry or wet materials. Materials are fed onto the belt, and magnetic particles adhere to the belt while non-magnetic particles fall away, allowing for the recovery of valuable materials and the removal of contaminants from products like grain, minerals, and recycled goods.
Roller mills – Roller mills are basically of two distinct types. The first has a series of rollers which rotate around a central axis within a drum. The reduction takes place between the rollers and the drum. The second type is where there are a series of fixed rollers and a rotating table. The milling takes place between the rollers and the table. This type of mill is used for dry grinding only and accepts only relatively soft materials. Small machines can have a throughput of only a few tens of kg per hour whereas larger machines are capable of handling up to 40 to 50 tons per hour and occasionally more. Feed size varies according to the machine. The machines are often fitted with screens for closed circuit grinding. Product size can be controlled by changing screens.
Roller pitch -It refers to the distance between the centres of adjacent rollers. In case of roller chain, pitch refers to the distance between the centres of adjacent rollers on a chain link. Itis a key dimension for identifying and selecting the correct chain size.
Roller press – Roller press is considered the global standard technology to produce pillow-shaped briquettes using diverse types of feed stocks. The roller press works on the principle of pressure and agglomeration. It consists of dual cylindrical rollers of the same diameter, rotating horizontally in opposite directions on parallel axes. The two rollers are arranged in such a way that a small gap exists between them and the distance from each other depends on factors such as the feed stock type, the particle size, the moisture content, and the addition of binders. During operation, the raw material is fed into the press and forced through the gap between the rollers on one side. It is then pressed into a die forming the densified product, which comes out on the opposite side. The smooth production of briquettes using this technology needs high quality rollers with dies on which the briquettes are shaped. The type of roller or die used determines the shape of the briquettes and typical bulk densities range from 450 kilograms per cubic meter to 550 kilograms per cubic meter.
Roller pump – It is also known as a peristaltic pump. It is a positive displacement pump which moves a fluid by compressing a flexible tube or hose with rollers or wipers attached to a rotor. This rolling action creates a sealed compression point which traps fluid and forces it through the tube, allowing for accurate dosing and fluid isolation from mechanical components.
Rollers, powered – The rollers of a powered roller conveyor is fundamentally different from those of the unpowered roller conveyor in that the barrel and the shaft portion are integral so that they can be driven by connecting power to their shaft ends. The integral shafts are mounted on bearings housed in the frames at two sides. These are termed as driven rollers. The driven rollers are normally subjected to considerable impact load (specially the reversing type processing conveyors) and hence they are made stronger. The rollers can be made from solid steel forgings or castings or can be fabricated from heavy section of pipes, tubes, and solid shafts, machined all over for proper static and dynamic balancing.
Roller setting – It refers to the configuration and adjustment of the levelling rollers (and sometimes backup rollers) to achieve the desired flatness and stress distribution in a metal strip or sheet.
Roller stamping die – It is an engraved roller used for impressing designs and markings on sheet metal.
Roller straightening – It is the straightening of extrusions by through a series of small diameter, staggered, rolls.
Rollers, unpowered – The normally used rollers are cylindrical rollers which are made from electric resistance welded (ERW) steel pipes with cast or fabricated end flanges to accommodate the anti-friction bearings (normally ball bearings). The through axles are stationery and roller barrels can rotate freely. These rollers are called idler rollers. For conveying, cylindrical objects (drums, pipes, round steel bars etc.), double tapered rollers, or wheel rollers are used.
Roller table – It forms the conveying system for the movement of the work-piece in the rolling mill. It consists of a series of roller either driven by line shafting and bevel gears from a common drive or by individual motors. In some improved designs, the bevel gears have been replaced with spur gears. The roller tables serve to feed the material being rolled into the rolls and receive it from the rolls. Hence, the roller table operates under severe conditions of mechanical impact, repetitive short-term duty cycles and dynamic transients (acceleration and decelerations). The roller table connects the separated stands of large and medium sized mills. There are required on majority of the mills for conveying the rolled stock towards as well as away from rolling stand.
Roller thrust bearings – These bearings much like ball thrust bearings, handle thrust loads. The difference, however, lies in the quantity of weight the bearing can handle. Roller thrust bearings can support significantly larger quantities of thrust load, and are therefore found in car transmissions, where they are used to support helical gears. Gear support in general is a common application for roller thrust bearings.
Roller transport – It refers to a system of moving goods or materials using a series of rollers, typically within a warehouse or production facility. These systems can be gravity-fed or powered, facilitating efficient and automated movement of loads.
Roll fatigue – Fatigue damage can start at the surface or sub-surface. Rolls are also damaged because of fatigue. The damage due to fatigue can start at the surface or the sub-surface. The problem of fatigue in the rolls can arise because of the high loads in the mills. Corrosion fatigue can also be a problem. With corrosion fatigue, there is no safe operation at all, and there is no fatigue limit.
Roll flattening – It is the flattening of metal sheets which have been rolled in packs by passing them separately through a two-high cold mill with virtually no deformation. It is not to be confused with roller leveling. It also refers to the elastic deformation or bending of the rolls themselves under the pressure of the rolling force, which affects the strip’s crown and flatness. It directly impacts the final shape and flatness of the rolled strip. If the rolls flatten excessively, it can lead to variations in the strip’s thickness and unevenness, known as ‘crown’.
Roll force – It refers to the compressive force applied by the rolls during the rolling process, specifically the force exerted by the rolls on the metal being deformed to reduce its thickness or change its cross-section. There are two normal ways of applying the force to the rolling stock. Therse are screw system and hydraulic system. Screw system uses the basic principle of the screw to adjust the space between the mill rolls. Since in this system, metal touches metal, these configurations wear down over time and can cause quality problems. In hydraulic system, fluid pressure is used to rapidly adjust the roll spacing several times per second. These minute, instantaneous adjustments allow for superior gauge tracking and higher quality products. Roll force is also known as roll separating force. It is the force which the rolls apply to the material to reduce its thickness and change its shape during the rolling process. It is the force which is exerted by the rolls on the work-piece during the deformation process, causing the material to change shape and thickness. Understanding and controlling of roll force is crucial for achieving desired product dimensions, surface quality, and material properties.
Roll forging – It is a process of shaping stock between two driven rolls which rotate in opposite directions and have one or more matching sets of grooves in the rolls. It is used to produce finished parts or preforms for subsequent forging operations.
Roll forming – It is a metal forming through the use of power-driven rolls whose contour determines the shape of the product. It is sometimes used to denote power spinning. Roll forming is a type of rolling involving the continuous bending of a long strip of sheet metal (typically coiled steel) into a desired cross-section. The strip passes through sets of rolls mounted on consecutive stands, each set performing only an incremental part of the bend, until the desired cross-section (profile) is obtained. Roll forming is ideal for producing constant-profile parts with long lengths and in large quantities.
Roll gap – It refers to the space or distance between the two rotating cylindrical rolls through which a material (like metal) is passed to reduce its thickness and / or shape it.
Roll grind – It is the uniform ground finish on the work rolls which is imparted to the sheet or plate during rolling.
Roll grinding machine – It is a specialized piece of equipment which is used to precisely grind and finish the surfaces of rolls used in rolling mills, ensuring accurate and high-quality metal shaping and forming. These rolls, crucial for shaping metal, can wear or become uneven, leading to defects in the final product, necessitating the use of roll grinders for maintenance and repair. Roll grinding machines are necessary for maintaining the quality and performance of rolling mills by precisely grinding and finishing the surfaces of the rolls.
Roll grooves – These refer to the shaped indentations or channels on the surface of the rolls which shape the metal stock as it passes through the mill. There are different types of grooves which are used for rolling of sections. Common grooves are rectangular box grooves, diagonal grooves such as squares and rhombic grooves (diamonds), round or false round grooves as well as oval grooves. Grooves can be symmetric, asymmetric and slit. Important parameters of grooves are height (depth), groove angle, relief radius, bottom radius, widths at collar, top, and middle bottom and middle bottom deflection. Normally, a combination of grooves is used in the roll pass design.
Roll hardness – It is the hardness of the material of a roll. Roll hardness is to be optimum. Higher hardness improves wear resistance but increases the risk of roll failure. Higher hardness also creates issues during machining and grinding of the rolls. It is not a fact that everything improves in the roll if hardness is higher. In fact, opposite is valid.
Rolling – It is a motion of two relatively moving bodies, of opposite curvature, whose surface velocities in the common contact area are identical with regard to both magnitude and direction. It is a type of motion which combines rotation (normally, of an axially symmetric object) and translation of that object with respect to a surface (either one or the other moves), such that, if ideal conditions exist, the two are in contact with each other without sliding. Rolling is also the reduction of the cross-sectional area of metal stock, or the general shaping of metal products, through the use of rotating rolls. Pure rolling is with no sliding and no spin.
Rolling and forging laps – Laps are elongated surface discontinuities which occur during rolling or forging operations due to the presence of some excessive material (fin) that is folded over. They can result because of oversized passes and blanks or improper handling of the material.
Rolling bearings – These are anti friction bearings or rolling element bearing. These bearings use rolling elements (balls or rollers) to reduce friction. In these bearings, axial, thrust, and moment loads can be supported depending on the bearings and how they are mounted. These bearings can be non-recirculating (limited range of motion, extra low friction) or recirculating (unlimited range of motion). These bearings are essential for reducing friction which enables majority of the machinery to operate efficiently and indeed even to exist. In fact, the first widespread application of rolling element bearings has been to enable the first transportation revolution (the bicycle) to take off. Rolling element bearings also enabled a revolution in manufacturing by making it possible to rapidly design and manufacture low-cost high precision machines, such as lathes, mills, and robots which in turn have helped to rapidly increase productivity. Although rolling bearings are ubiquitous, designing with them needs significant care.
Rolling contact – It describes the movement where one surface rolls over another, like a ball bearing, considerably reducing friction and wear compared to sliding. This interaction involves elastic deformation of the contacting surfaces under applied loads, generating repeated stresses which can cause fatigue and failure in materials, a phenomenon known as rolling contact fatigue. It is a key principle in the design of components like bearings, wheels, and gears, which rely on rolling motion to transmit loads and facilitate rotation.
Rolling-contact fatigue – It is the repeated stressing of a solid surface because of the rolling contact between it and another solid surface or surfaces. Continued rolling-contact fatigue of bearing or gear surfaces can result in rolling contact damage in the form of sub-surface fatigue cracks and / or material pitting and spallation.
Rolling-contact wear – It is the wear to a solid surface which results from rolling contact between that surface and another solid surface or surfaces.
Rolling direction – It refers to the direction in which a metal is rolled during processing, which is perpendicular to the axes of the rolls, and is often significant for the final properties and appearance of the metal product.
Rolling-element bearing – It is a bearing in which the relatively moving parts are separated by balls, rollers, or needles.
Rolling equipment – It consists of roll stands, rolls, chocks, bearings, drives, and entry and exit guides.
Rolling friction – It is also called rolling resistance. It is defined as the force which resists one solid rolling on another.
Rolling joint – This joint consists of two interfacing segments aligned perpendicularly to each other that share a moving point of contact. Cables are employed to hold the individual segments together. This type of joint has two degrees of freedom (DOF) in three dimensions.
Rolling load – It refers to the force exerted on the rolls and supporting structures during the metal deformation process as the metal stock is passed through the gap between the rolls. It is the load with which the rolls press against the metal.
Rolling mandrel – In ring rolling, it is a vertical roll of sufficient diameter to accept different sizes of ring blanks and to exert rolling force on an axis parallel to the main roll.
Rolling mill – It consists of machines which are used to decrease the cross-sectional area of metal stock and to produce certain desired shapes as the metal passes between rotating rolls mounted in a framework comprising a basic unit called a stand. Cylindrical rolls produce flat shapes, while grooved rolls produce rounds, squares, and structural shapes. Different types of rolling mills are four-high mill, Sendzimir mill, and two-high mill.
Rolling mill cooling bed – It is used for the uniform air cooling of the rolled materials (bars or profiles normally referred as ‘bars’) and transport it in a phased manner from the entry side of the cooling bed to its discharge side. It transfers the bars one by one to the roller table, on which they are transported to the finishing section. It is important equipment in the hot rolling of long products in a rolling mill. A cooling bed carefully moves and cools the hot steel rolled bars after the hot rolling process. Cooling beds are to be specifically designed considering the smallest and the maximum size of the bars being rolled in a particular rolling mill. They are designed for receiving, transferring, and cooling of the rolled material. They are sized so that the product cools within a particular cycle time. The length of the cooling bed is determined by the maximum run-out bar length, optimized by the selling lengths to minimize crop losses. The width of a cooling bed is determined on the basis of mill productivity (tons per hour) and the time required for cooling. Cooling beds normally have natural air cooling. However, for achieving faster cooling of the bars, blowers can be installed for blowing air from the bottom of the hot bars.
Rolling mill equipments – These equipments play a very important role in production of the wire rods. The rolling mill optimization, operational flexibility, and the process reliability play a fundamental role. In order to improve the finished product quality (in terms of size tolerances, mechanical properties and surface finish), a reliable and dedicated automation system is also needed. Different automation systems are implemented in modern rolling mills to control thickness/section, the angular speed of the rolls, and the tension between the stands and the related temperatures. Specific thermo-mechanical processes and automated control systems have been developed to enhance the technological properties, tolerances and surface quality of the rolled product.
Rolling mill guide equipments – In hot rolling mills for long products, guide equipments guide the rolling stock at the entry and the exit of the roll pass so as to have smooth rolling of the rolling stock. The guiding equipments are to be sturdy, accurate and stable. Rolling mill guide equipments play a major role in ensuring the surface quality of the rolled product. The guides are to be designed for the wide variety of stock sizes and shapes which are normally encountered in the long product rolling. The guide equipments are usually classified in three ways namely (i) position with respect to the working stand (e.g. entry guide and exit guide etc.), (ii) method of construction, and (iii) type of friction between the rolling stock and the working element of the guide equipment (e.g. sliding or rolling etc.).
Rolling mill scheduling – It involves the systematic planning and organization of various production tasks within a mill facility. It encompasses the coordination of processes such as heating, rolling, and cooling to ensure a continuous flow of materials and efficient utilization of equipment. The scheduling process is essential for meeting production targets, maintaining product quality, and minimizing downtime. The role of scheduling in managing production processes cannot be overstated. It acts as a bridge between the demand for finished products and the capabilities of the rolling mill. Scheduling involves creating a timeline that optimally sequences tasks, from preparing raw materials to the final product’s dispatch. Key terms and concepts in the scheduling include job sequencing, batch processing, lead times, and setup times.
Rolling mill shears – A number of shears are installed in a rolling mill. Rolling mill shears are used to cut steel bars, plates, or other shapes into smaller sizes, either during the rolling process (hot shears) or after (cold shears). Shears are crucial components in rolling mills. Each shear has different objective. Hot shears are used before the cooling bed. These shears cut the metal while it is still hot. Cold shears are used after the cooling bed These shears cut the finished steel products to their required length. Types of shears include (i) flying shears which are synchronized with the rolling speed to provide an accurate cut during the rolling process, (ii) rotary Shears which are used for cutting bars, plates, and other shapes, (iii) crank shears which are a type of flying shear that can be semi-automatic or fully automatic, (iv) cropping shear which is used for cropping both ends of the rolling stock being rolled,(v) cooling bed shear which cuts the rolled bar in cooling bed length, and (vi) dual shears which are a combination of rotary and lever shear used for cutting to cooling bed lengths.
Rolling mill stands – These are the most essential equipment in the rolling mill process. A rolling mill stand is normally fitted with a number of rolls through which the work-piece bar is passed giving it the required cross-section. There are different designs of mill stands each having different applications to the rolling process.
Rolling motion – It is the combined translational motion (moving from one point to another) and rotational motion (spinning) of a rigid object, such as a wheel, cylinder, or ball, moving across a surface. This motion is characterized by the object both moving its centre of mass and rotating around an axis, typically its own axis of symmetry. For pure rolling (without slipping), the point of the object in contact with the surface is momentarily at rest. This phenomenon is crucial for analyzing the energy, forces, and stability of several engineering systems, from the movement of vehicles to the dynamics of machines.
Rolling over – It is the operation of turning flask over to reverse its position. It is the positioning of the mould so that the pattern faces upward in order to be removed.
Rolling passes – These refer to the distinct stages in the rolling process where a workpiece is subjected to deformation, typically involving multiple passes which can optimize properties such as void closure and material integrity. The effectiveness of these passes is influenced by factors like reduction ratios and temperature conditions.
Rolling pressure – It refers to the force exerted by the rolls on the metal being processed, leading to its deformation and shaping. This pressure is crucial for achieving the desired thickness, shape, and mechanical properties of the rolled product. The pressure applied by the rolls causes the metal to deform plastically, meaning it changes shape permanently. Roll pressure is a useful quantity for characterizing the mechanics of the rolling process. It is the average normal stress, pressure, acting between the work piece and roll. The pressure is not constant since the stress acting to deform the work piece is the stress needed to overcome material strength, frictional forces, and any constraints placed on the deformation by process characteristics.
Rolling resistance – It is also called indentation rolling resistance. It is the force which opposes motion because of the belt’s bottom cover indenting around idler rollers. This occurs since the rubber of the belt cover is viscoelastic, meaning it does not instantly regain its original shape after being compressed by the idler, creating an asymmetric stress that hinders forward movement. This energy loss is a major component of a conveyor’s total motion resistance, especially in long-haul systems, and depends on factors like belt properties, load, idler diameter, and temperature.
Rolling schedule – It plays a decisive role in rolling of strip in HSM. Traditionally, the most important factor is the evolution of the profiles of the rolls in the mills caused by their wear and thermal expansion. From this derives the `coffin’ schedule which means start narrow, quickly build up to wider material as the thermal crowns increase on the rolls, and gradually fade back to narrow as the rolls wear. Rolling schedule has an important effect on the capability of mill. The rolling mill schedule includes reduction, speed, and temperature schedules. Reduction schedule determines rolling passes and the reduction per pass. Speed schedule determines the bite speed, through speed and maximum rolling speed without variation in acceleration and deceleration of the motor. Temperature schedule controls the temperature drop of mill house and finish rolling temperature by cooling water flow according start rolling temperature. The issues which are important for the rolling schedule are (i) the shape of the strip is good and the crown meets the specifications requirement, (ii) the yield of rolling mill, and (iii) the good performance of strip. The rolling schedule is to ensure that the strips produced in the hot strip mill meets the requirements of dimensions, comprehensive properties and microstructure of the strip.
Rolling sequence – It refers to the specific order and parameters (like temperature, reduction, and pass time) of successive passes or ‘stand’ (pairs of rolls) used to deform metal stock and achieve a desired final shape or thickness.
Rolling slab – It is a rectangular semi-finished product, produced by hot rolling fabricating ingot and suitable for further rolling.
Rolling speed – It refers to the surface speed of the rolls, which is the velocity at which the metal strip is drawn through the gap between the rolls during the rolling process. In the context of physics, rolling speed refers to the linear speed of the centre of mass of a rolling object, which is related to its rotational speed and radius.
Rolling stock – It refers to any railway vehicle which moves exclusively on rails or a tracked transport system. The term includes all powered (e.g., locomotives) and unpowered vehicles (e.g., passenger carriages or coaches and goods wagons etc.).
Rolling velocity – It is the mean of the surface velocities of two bodies at the area of contact. Occasionally the sum of the velocities is quoted instead of the mean.
Roll lathe – It is a specialized lathe which is designed for turning and processing the cylindrical rolls used in rolling mills.
Roll magnetic separator – It is an industrial equipment which uses powerful magnets and a moving belt to separate magnetic materials from non-magnetic materials in a dry, free-flowing feed stream. Material is fed onto a belt that travels over a stationary magnetic roll (or rolls). Magnetic particles are held to the magnetic roll by the magnetic field until they move out of the field and are discharged, while non-magnetic particles fall freely, allowing for purification of products in industries like food processing and mineral processing.
Roll marks – Roll marks are ‘embossed’ elevations or depressions normally recurring periodically and varying greatly in shape and size. The defect can be normally detected with the naked eye or with a low magnification on the scaled or descaled sample. If the defect occurs as elevations on the surface of the rolled product, it is caused by depressions of various kinds in the rolls themselves or in the pinch rolls. Depressions in the wire rods are caused by elevations on such installations, e.g., chips and remnants of scale.
Roll materials – These are the materials from which the rolls are made. In the rolling of steels, the material of the rolls is to be capable of withstanding loads which plastically deforms the rolling stock without itself being plastically deformed. In the rolling of hot steel this is not a difficult problem and iron or steel rolls are suitable if they are operated at a temperature considerably lower than that of the rolling stock. Whether iron or steel rolls are used in any particular case depends on the specific duty they have to perform and whether toughness, resistance to thermal cracking or shock loading or hard-wearing properties is most important. Rolls can be classified as per the roll materials and the method of manufacture, the first main subdivision being (i) iron rolls, (ii) steel rolls, and (iii) carbide rolls (made from tungsten carbide). This division depends on the carbon content of the material. In the case of rolls the demarcation line is normally taken at around 2.4 % C. Normally rolls are referred as being steel base below this figure, and iron base above this figure. There is a marked structural distinction between these two types as there is no free graphitic carbon in steel base rolls. Steel rolls can be either cast, or forged so giving a further subdivision. One other division which cuts across the above classification is that of double poured duplex rolls which may be cast with a hard metal outer surface and a tougher and stronger metal forming the centre of the roll.
Rollover board – It is a wood or metal plate on which the pattern is laid top face downward for ramming the drag half mould, the plate and half mould being turned over together before the joint is made.
Rollover burr – It is the burr which is formed by a cutter when it exits over a surface and allows the chip to be rolled away from the cutter, rather than sheared.
Rollover machine – It is a moulding machine with which the flask is rolled over before the pattern is drawn from the mould.
Roll pass – It refers to the grooves or shapes cut into the rolls of a rolling mill to deform and shape metal stock into a desired profile or cross-section. Rolling is carried out between grooved rolls. Two opposite grooves in the collaborating rolls form a pass, which corresponds to a work piece’s cross section shape expected after the pass. After every pass, the cross section decreases and its shape becomes closer to a shape of the final product.
Roll pass design – Development of subsequent pass shapes and its proper location on the rolls is called the roll pass design. It consists of a set of methods for determining the dimensions, shape, number, and type of arrangement of rolling mill passes. Roll pass design also includes the calculation of pressing forces and their distribution on the roll passes. It is an innovative technique to ensure stability, flexibility, and quality in a rolling mill which is rolling rounds and shapes. It involves the calculation of pressing forces and cutting grooves in the roll body through which steel bar which is being rolled is made to pass sequentially and achieve the required contour, shape and size. With roll pass design, a person can determine the shape, dimensions, number, and type of arrangement of rolling mill passes. It is also be possible to carry out power calculation through simulation (gear ratios, motor sizes, and rolling). Roll pass design is an essential part of long product rolling process, since the long products are rolled between the shaped rolls in the long product rolling mills. Roll pass design generally means the cutting of grooves in the roll body through which steel to be rolled is made to pass sequentially to get the desired contour and size. The primary objective of the roll pass design is to ensure production of a product of correct profile within the tolerance limits, free of defects, with good surface quality and the required mechanical properties.
Roll pickup – It consists of small particles of metal and metal oxide generated in the roll bite, which subsequently transfer to the rolled product. It can be distributed uniformly and / or in streaks.
Roll pressure – It refers to the light load applied by pressure rolls to coated products to improve the adhesion and retention of coatings. This pressure can be adjusted through the height of the roller and the downward force exerted on the products.
Roll pressure distribution – It refers to the variation of pressure exerted by the rolls on the workpiece along the contact arc. This pressure distribution is crucial for understanding and optimizing rolling operations, influencing factors like energy requirements and the final product’s quality.
Roll radius – It is the radius of the rolls used in the rolling process, which is a critical parameter which influences the roll bite angle and the quantity of thickness reduction during metal forming.
Rolls – Rolls are the basic part of a roll stand and are normally the most vital and very costly part of a rolling mill. The rolling stock is plastically deformed between the rolls. Rolls ensure the required shape, dimension and surface quality of the rolled product. They transfer the force and torque load. The deformation of rolling stock is directly accomplished by the rolls. Rolls are needed to carry out the heavy work of reduction of the cross section of the metal being rolled. Rolls have to take all kind of stresses, loads from normal and abnormal rolling and which are changing with the roll wear during a rolling campaign. Roll are required never to break, spall or wear. They are expected to give excellent performance without causing any problems. Under the conditions of rolling, the contact area of the roll which comes in contact with the rolling stock suffers wear, while other parts of the roll body and roll necks does not experience plastic deformation or fatigue but are under high loads.
Roll separating force (RSF) – It is the force needed to separate the rolls and deform the material, typically measured as the force per unit width. It is a critical parameter in rolling process design, influencing factors like roll strength, power consumption, and the final shape and size of the rolled product.
Roll shifting technology – Different roll shift shape control technologies have been developed. These technologies basically consist of (i) a method by which the shape control effect can be improved by shifting rolls, reducing the contact portion between rolls outside the strip width and as a result to improve the deflection of the rolls, and (ii) a method by which the shape control effect can be improved by shifting specially shaped rolls, and producing the geometric roll gap distribution change effect in the width direction. Out of different roll shift methods, the method based on the effects of geometrically shaped shift rolls has the advantages in that the shape control effect can be freely set by the geometric shape. A numerical control roll grinding machine makes it possible to more freely set the grinding roll curve, and more easily improve the effect of the optimized roll curve. Basically, the same shift mechanism is used in the above mentioned two methods but the geometrically shaped shift rolls are more effective. The geometrically shaped shift rolls have a roll profile which has simple concave and convex combined curve (S-shaped curve). The shift rolls profile can be optimized and the optimally-shaped shift roll is also sometimes called as a ‘combined numerical profile’ (CNP) roll. Roll shift method is further aided by an automatic setting system which simultaneously calculates the setting values for the shift positions and roll bending pressures and provides commands, according to the roll shape. Further, the shift roll shapes can be optimized for each rolling mill plant or rolling mill stand can be optimized, and the shape of shift rolls of a rolling mill stand can be optimized one by one so that the control effect for the strip width with a higher production ratio becomes higher. To thoroughly optimize the roll shape, the shape is frequently determined not by using specific functions, but by using numerical data. The work roll shift method can also be used for roll wear dispersion to reduce step wise uneven wear on rolls in hot rolling of the steel strip.
Roll shop – It is the area or department which is responsible for the maintenance, repair, and preparation of the rolls used in the rolling process, ensuring they are in optimal condition for producing high-quality rolled products. The functions of the roll shop include (i) to receive roll assembly from the rolling mill after completion of a rolling campaign, (ii) to wash the roll assembly and dismantle the rolls from the assembly, (iii) inspection of the rolls for fire cracks, measurement of diameter, and inspection of the individual parts of the rolls and roll bearing and rotating them wherever necessary, (iv) planning and carrying out grinding / regrooving of the rolls as per plan, (v) storing of ground / regrooved roll in roll racks where these rolls wait for their assembly as per rolling schedule of the mill, (vi) dismantling of the chocks and sending them to assembly area for assembling the ground / regrooved roll as per the rolling schedule, (vii) carrying out the assembly of the roll and chock in pairs, and (viii) sending the assembled roll pair to rolling mill.
Roll stand – It is the fundamental structural unit which houses and supports the rolls, which are used to shape and reduce the thickness of materials. Roll stands are essential components in rolling mills, playing a crucial role in the rolling process by housing and supporting the rolls which deform the metal stock.
Roll stand housing – Roll stand housing creates a framework of the rolling mill stand and for absorbing the total metal pressure on rolls during the process of rolling. Hence, the housing is to be solid and its structure is to enable easy and fast roll changing. Its construction and dimensions have to take into account the sizes of various other elements. Also, there need to be easy access to all parts of the housing and other details of the roll stand. Each of the roll stands has two housings, in which rolls are placed with chocks (bearings). In the upper part of the housing, there are adjusting screws (screw down mechanism) and the roll counter-balancing device along with their drives. The housings need high rigidity, sufficient strength for taking the loads, simplicity of design and minimum cost of production. From the structural viewpoint, the housings can be classified into three types. These are (i) enclosed housing where the whole housing is made of one piece and which is more beneficial from the strength point of view, (ii) open housing which has the separated cap, connected to the housing by screws for easier rolls changing, and (iii) housing-less roll stand which has rigid chocks connected by solid and pre-stressed joints. The housing-less roll stand has limited stress relaxation (spring-back) of rolls and has smaller and lighter structure.
Roll straightening – It is the straightening of metal stock of different shapes by passing it through a series of staggered rolls, the rolls normally being in horizontal and vertical planes, or by reeling in two-roll straightening machines.
Roll texturing machine – It is a device which utilizes techniques like electrical discharge texturing (EDT) to create controlled surface textures on work rolls, which in turn transfer these textures to the rolled products.
Roll threading – It is the production of threads by rolling the piece between two grooved die plates, one of which is in motion, or between rotating grooved circular rolls. It is also called thread rolling.
Roll transfer car – It is a piece of equipment which is used to transport rolls (both work and backup rolls) between the mill bay, across the bays and the roll shop for maintenance, storage, or replacement. Roll transfer cars facilitate the efficient and safe movement of heavy rolls, which are crucial components in rolling mills, used for shaping metal into various products. These cars are designed to handle the weight and size of rolls, often using a combination of manual and automatic controls for precise positioning and movement.
Roll turning machine – It is also known as a roll lathe. It is a specialized machine which is used in rolling mills to accurately machine and shape the cylindrical rolls used in metal forming processes, improving productivity and product quality. These machines are mainly used for the regrooving of the rolls used for shape rolling. Roll turning machines, particularly CNC (computer numerical control) lathes, are designed to precisely machine the surfaces of rolls used in rolling mills. These machines are crucial for maintaining the quality and consistency of the rolled metal products, as the shape and surface finish of the rolls directly impact the final product.
Roll welding – It is the solid-state welding in which metals are heated, then welded together by applying pressure, with rolls, sufficient to cause deformation at the faying surfaces. It is a process in which two or more sheets or plates are stacked together and then passed through rolls until sufficient deformation has occurred to produce solid-state welds. Two modes of roll welding are common. In the first, the parts to be welded are merely stacked and passed through the rolls. The second method, normally termed pack rolling, involves sealing the parts to be rolled in a pack or sheath and then roll welding of the pack assembly is done. The first method is more generally used in the cold welding of ductile metals and alloys. Sometimes the stack to be welded is first tack welded at several locations to ensure alignment during rolling. Also, when using this method, the deformation during the first rolling pass is required to exceed the threshold for welding (typically higher than 60 % for cold rolling) to keep the parts together. The required first pass reduction can be reduced by hot rolling, if the metals to be rolled can tolerate preheating without excessive oxidation. Once the first pass has been accomplished, the reduction per pass can be decreased, as is frequently desirable because roll-separating forces increase as the parts to be rolled become thinner. However, the non-uniform stress distribution which builds up during a sequence of very light passes can cause the weld to open up or ‘alligator’. Hence, the reduction for subsequent passes is normally a compromise between applying excessive separating forces and ‘alligatoring’. In pack roll welding, the parts to be welded are completely enclosed in a pack that is sealed (typically by fusion welding) and frequently evacuated to provide a vacuum atmosphere. This can be accomplished by a frame that surrounds the parts to be welded, which is sandwiched by two lids, or can simply consist of two covers formed to encapsulate the parts to be welded. Semi-killed or killed low-carbon steel is a common material for the pack, but is not suitable for all alloy and temperature combinations. Although the preparation costs of pack roll welding are significant, the process has the advantages of (i) providing atmospheric protection, which can be particularly important for reactive alloys such as those of titanium, zirconium, niobium, and tantalum, and (ii) permitting welding of complex assemblies involving several layers of parts. A significant limitation of the process is that packs become difficult to process when their length exceeds a certain length.
Romelt process – It is a process for ironmaking. It is a smelting reduction process for the production of hot metal (liquid iron). It is a single stage liquid-phase iron reduction process. In the process, the iron bearing materials are supplied to the slag bath by gravity and agitated by gas. They dissolve in slag. Iron oxides are reduced from slag with the help of coal carbon, which is also supplied by gravity and blown into the bath. In order to intensify heat and mass transfer slag bath bubbling with oxidizing gas, which is injected under the surface of the slag, is carried out. Gas containing carbon mono-oxide and hydrogen evolves from the melted slag. The evolved gas is combusted at the top. The heat of this post combustion mostly provides thermal energy for the reactions taking place in the slag bath. A key element of effective process to take place is the active heat transfer between the zone of post-combustion and slag bath. The special features of the Romelt process include (i) flexibility to use wide range of iron bearing materials, (ii) no preparation needed for the raw materials, (iii) use of non-coking coal as fuel and as reducing agent, (iv) supporting production units such as coke-ovens and sintering plant are not required, (v) has capacity to generate sufficient power to meet overall plant requirements including oxygen plant, (vi) reduces the cost of hot metal as compared to blast furnace route, and (vii) can be used for waste processing in which case the cost of hot metal is further reduced.
Roof beam – It is a horizontal, load-bearing structural element designed to support the weight of the roof and its associated loads, transferring this weight to vertical supports like columns or walls. These beams resist bending moments and shear forces, contributing to the overall strength, stability, and structural integrity of a building. They can be made from different materials, including timber, steel, and reinforced concrete, and come in different shapes and types depending on their specific function within the roof structure.
Roof beam and shuttering layout drawing – A roof beam is made to strengthen the overall structure of a building. A roof beam is a triangular structure which is normally made on the top of the building.
Roof, building – It is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of temperature, and wind. A roof is part of the building envelope. The characteristics of a roof are dependent upon the purpose of the building that it covers, the available roofing materials, the local traditions of construction, wider concepts of architectural design and practice, and can also be governed by the statutory regulations.
Roof, furnace – It refers to the top surface or cover of a furnace, acting as a vital part of the furnace’s design for heat retention, safety, and process control.
Roofing sheet – It is coiled or flat sheet in specific tempers, widths, and thicknesses suitable for the manufacture of corrugated or V-crimp roofing.
Roof slab – It is a horizontal, structural element, typically made of reinforced cement concrete (RCC), which forms the roof of a building, serving as the upper covering exposed to outdoor conditions. It functions as a structural component to bear and transfer loads, such as dead load (its own weight) and live load (occupancy, environmental factors), through bending action to the supporting beams or walls. Roof slabs also provide weather protection and act as a ceiling for the level below.
Roof slab layout drawing – The roof slab layout drawing is more prominently made in the AutoCAD architectural software. The main purpose of the roof slabs is to provide a detailed account of the floors, roof faces, and other such surfaces which need precise edge information.
Roof truss – It is a prefabricated, triangular-shaped structural framework designed to support a building’s roof by distributing the roof’s weight (including dead, live, snow, and wind loads) evenly across the supporting walls or columns. Composed of interconnected members forming triangles, which are inherently stable, trusses efficiently transfer loads through compression and tension at the joints. This design allows for large, open spaces underneath the roof without the need for interior columns and supports.
Room-and-pillar mining – It is a method of mining flat-lying ore deposits in which the mined-out area, or rooms, are separated by pillars of approximately the same size.
Room relative humidity (RH) – It is the percentage of water vapour present in the air inside a room compared to the maximum quantity of water vapour the air can hold at that specific temperature and pressure. It is a critical metric in building design, heating ventilation air conditioning (HVAC) systems, and industrial processes since it directly affects thermal comfort, condensation risks, and the potential for mold, mildew, and corrosion.
Room temperature – It refers to the range of temperatures which are normally considered comfortable for human occupancy, typically between 20 deg C to 25 deg C. In engineering contexts, room temperature serves as a standard reference point for different experiments and measurements, frequently used when specific temperature control is not necessary. Room temperature dry normally refers to a storage environment which is neither excessively hot nor cold, and also has low humidity, typically around 20 % to 30 %, to prevent moisture-related issues. Room temperature wet refers to the wet-bulb temperature, which is the lowest temperature achievable through evaporative cooling of air, typically measured using a thermometer with a wet cloth around its bulb.
Room-temperature curing adhesive – It is an adhesive which sets (to handling strength) within an hour at temperatures from 20 deg C to 30 deg C and later reaches full strength without heating.
Room-temperature vulcanizing (RTV) – It consists of vulcanization or curing at room temperature by chemical reaction. It normally applies to silicones and other rubbers.
Room-temperature-vulcanizing silicone – It is a type of silicone rubber which cures at room temperature. It is available as a one-component product, or mixed from two components (a base and curative). Manufacturers provide it in a range of hardnesses from very soft to medium (normally from 15 Shore A to 40 Shore A. Room-temperature-vulcanizing silicones can be cured with a catalyst consisting of either platinum or a tin compound such as dibutyltin dilaurate.
Root – It is non-standard term for joint root and weld root.
Root bead – It is a weld which extends into or includes part or all of the joint root.
Root cause analysis (RCA) – It is also known as root cause failure analysis (RCFA). It is a method of problem solving used for identifying the root causes of faults or problems. It is the process of investigating how an equipment failure, process problem, quality problem, safety incident, environmental incident, and several other problems in a plant has happened. It is widely used analysis process. Root cause analysis is a form of inductive inference (first create a theory, or root, based on empirical evidence, or causes) and deductive inference (test the theory, i.e., the underlying causal mechanisms, with empirical data). Root cause analysis can be decomposed into four steps namely (i) identify and describe the problem clearly, (ii) establish a timeline from the normal situation until the problem occurrence, (iii) distinguish between the root cause and other causal factors (e.g., through event correlation), and (iv) establish a causal graph between the root cause and the problem. Root cause analysis normally serves as input to a remediation process whereby corrective actions are taken to prevent the problem from recurring.
Root crack – It is a crack in either the weld or heat-affected zone at the root of a weld.
Root edge – It is a root face of zero width.
Root face – It is that portion of the groove face adjacent to the joint root.
Root gap – It is a non-standard term for root opening.
Root locus – It is a graphical method for analyzing the properties of a transfer function as some parameter is varied.
Root mean square (RMS) – It is a term describing the surface roughness of a machined surface, calculated as the square root of the average of the squared distance of the surface from the mean line. The root mean square of a set of numbers is the square root of the set’s mean square. Given a set ‘Xi’, its root mean square is denoted as either ‘Xrms’ or ‘RMSx’. The root mean square is also known the quadratic meanM2 a special case of the generalized mean. The root mean square of a continuous function is denoted ‘frms’ and can be defined in terms of an integral of the square of the function. The root mean square value of a set of values (or a continuous-time waveform) is the square root of the arithmetic mean of the squares of the values, or the square of the function which defines the continuous waveform. Root mean square is also the statistical average value of the amplitude generated by a machine, one of its components, or a group of components. The root mean square value of a waveform is the direct current value which corresponds to equivalent heating value.
Root mean squared error (RMSE) – It is defined as the square root of the mean of the squares of all errors in numerical predictions, serving as a normal-purpose error metric. It is a measure of accuracy for comparing forecasting errors of different models or configurations for a specific variable, but it is scale-dependent and not suitable for comparing errors across different variables.
Root mean square (RMS) speed – The root mean square speed of gas molecules is the measure of the average speed of gas particles at a specific temperature. It is the square root of the average of the squared speeds of a group of values. It is a way to measure how fast gas particles moves in a particular direction.
Root opening – It is the separation at the joint root between the work-pieces.
Root penetration – It is the depth which a weld extends into the joint root.
Root radius – It is the rounded curvature at the base of a feature, such as a gear tooth or a notch in a material, which considerably influences the stress distribution and overall strength of the component. A larger root radius normally reduces stress concentrations at the root, improving fracture toughness and bending strength, which is a critical consideration in the design of gears and other structural elements.
Root reinforcement – It consists of weld reinforcement opposite the side from which welding has been done.
Roots blower – It is also known as a rotary lobe compressor or twin rotor blower, is a type of positive displacement blower that uses two counter-rotating, meshing lobes (or rotors) within a casing to trap and transport air or gas from an inlet to an outlet. It delivers a continuous, pulsation-free airflow by displacing fixed volumes of air without internal compression, with the pressure rise occurring against the system’s resistance. Roots blowers are oil-free and are used in several industrial applications like waste-water treatment, pneumatic conveyance, and as vacuum pump.
Roots-type pump – This lobe pump displaces the fluid trapped between two long helical rotors, each fitted into the other when perpendicular at 90-degree, rotating inside a triangular shaped sealing line configuration, both at the point of suction and at the point of discharge. This design produces a continuous flow with equal volume and no vortex. It can work at low pulsation rates, and offers gentle performance which some applications need.
Root surface – It is the exposed surface of a weld opposite the side from which welding was done.
Rope – It is a highly flexible, load-bearing structure of twisted or braided strands (made of wires or fibres) used to transmit tensile forces, lift loads, or convey objects. Unlike chains, ropes are redundant, multiple-element structures offering high load capacity and flexibility for applications such as suspension bridges, elevators, and safety systems.
Rope lay – It refers to the helical twist of wires within strands and the twist of strands around a rope’s core, defining the rope’s construction and characteristics. It specifies the direction of these twists (right-hand lay or left-hand lay) and the relationship between wire and strand twist directions (regular lay or lang lay). The direction and pattern of the lay impact considerably rope’s flexibility, abrasion resistance, and tendency to twist or kink.
Rope pump – It is a type of pump which uses a loose-hanging rope, which is lowered into a well and drawn up through a long pipe, with its bottom end submerged in water. Round disks or knots, matching the diameter of the pipe, are attached to the rope, allowing water to be pulled to the surface. The rope pump can be installed on boreholes or hand-dug wells, providing an affordable and efficient water-lifting solution.
Rope structure – It is a flexible, multi-element structure designed to withstand tensile loads, formed by twisting or braiding individual strands, wires, fibres, or yarns together. The most common type, steel wire rope, consists of helically wound steel wires forming strands, which then twist around a central core to create the rope. This layered construction provides high tensile strength, flexibility, and durability, with variations in construction, lay (direction of twist), and core material (steel or fibre) allowing for application-specific performance characteristics.
Roping – It is a ropelike appearance in the rolling direction after the metal has undergone severe deformation. Roping or looper lines, is also a phenomenon of surface roughening, witnessed during deep drawing. The name roping is linked to characteristic ‘roping’ marks on drawn shapes. The roping is also caused by non-uniform deformation, with non-uniformity linked to irregularities or heterogeneities in the structure. As an example, macro-segregation from the cast structure can produce striated structure or surface banding or roping marks. Alternatively, the roping can also develop from deformed grains or bands of fine grains of similar orientations. In both the cases roping can originate from earlier coarse grains.
Rosenthal solution – It predicts the temperature distribution caused by a moving point heat source. It has been developed for the quasi-steady-state conditions of processes like welding and provides a foundational analytical framework for understanding heat transfer. The solution assumes a semi-infinite solid with constant material properties and a moving, non-radiative point heat source, serving as a fundamental tool for process engineering and the design of heat-affected zones in different metal fusion and additive manufacturing applications.
Rosette – It is rounded configuration of microconstituents in metals arranged in spirals or radiating from a centre. It also consists of strain gauges which are arranged to indicate at single position strains in three different directions.
Rosette graphite – It is an arrangement of graphite flakes in which the flakes extend radially from the centre of crystallized areas in gray cast iron.
Rosin – It is a resinous material obtained from pine trees and other plants, mostly conifers. The primary components of rosin are diterpenoids, i.e., C20 carboxylic acids. Rosin consists mainly of resin acids, especially abietic acid. Rosin frequently appears as a semi-transparent, brittle substance which ranges in colour from yellow to black and melts at stove-top temperatures.
Rosin mildly activated (RMA) flux – It is a type of solder flux consisting of rosin, solvent, and a small amount of activator, designed for easily solderable surfaces, with low activity and often non-corrosive and non-conductive residues that may be left on the board.
Rosin super activated flux – It is s a type of solder flux. It consists of rosin with very strong activators. It has very high activity. There is a need for thorough cleaning of residues after soldering.
Rotameter – It is a variable-area flowmeter which measures the volumetric flow rate of a fluid by using a free-moving float inside a vertical, tapered (wider at the top) glass or metal tube. As the fluid flows upward, it lifts the float to a height where the upward drag force from the fluid equals the float’s weight, with the float’s position indicating the flow rate on a scale along the tube.
Rotary airlock valve – It is an airlock with an inlet and outlet. It is frequently used in industrial applications, where materials are to be controlled by, high or low pressures. It is also suitable for fluids with varying temperatures, and can withstand high pressures. There are several types of rotors used in rotary airlock valves, each of which performs well in different applications. The rotors in these valves vary in shape, diameter, and strength, and they are designed to minimize material and pressure losses. The rotor vanes are normally made from abrasion-resistant steel, making them perfect for use in corrosive environments. In addition, the rotary airlocks are also suitable for applications where the material that passes through the valve is too abrasive, or explosive. A proper design of a rotary airlock valve can greatly reduce the amount of leakage. In order to create the best seal possible, the body and end covers of a rotary valve must be heavy-duty and precision-machined. The rotor has a raised face inside the end cover, which ensures a proper seal and alignment with the housing. The shaft needs to be large enough to prevent deflection, and it should also be designed to fit tightly inside the housing.
Rotary compressor – It is a type of air compressor which uses one or more rotating elements, such as intermeshing screws or vanes, to move and compress a gas from low to high pressure in a continuous flow. Unlike piston compressors, rotary compressors provide a smooth and continuous output of compressed air, making them suitable for industrial applications which need consistent air delivery.
Rotary control valve – – It is a valve style in which the flow closure member (full ball, partial ball, disk, or plug) is rotated in the flow stream to control the capacity of the valve. This valve regulates fluid flow by using a rotating motion (like a quarter-turn) to open, close, or throttle the flow, unlike linear control valves which use a straight-line motion.
Rotary converter – It is an electric machine which converts electric power between two forms, say, alternating current and direct current or single-phase and three phase, or between two different frequencies of alternating current (the latter two can be performed by the same machine).
Rotary curing press – It is also called Roto-cure. It is a vulcanizing machine consisting of a rotating, heated drum with a flexible steel band partially encircling the drum, which continuously advances the belt while under pressure and heat between drum and band. It is a continuous vulcanization machine designed to produce conveyor belts and other rubber products by heating them under constant tension to ensure a smooth surface, uniform thickness, and durability. It consists of a steam-heated, revolving steel drum, which the rubber product moves around, and is used to cure different rubber sheets and materials.
Rotary die cutting – It is a special kind of die cutting which uses a cylindrical die to cut shapes out of material. It is a high-speed industrial manufacturing process which uses a cylindrical die rotating on a press to cut out shapes from a web of material, offering high accuracy and efficiency for large-volume production.
Rotary-draw bending – It is a cold bending method used to precisely shape pipes and tubes into curves with small, repeatable radii by clamping the workpiece to a rotating bend die and ‘drawing’ it around the die’s form. This versatile process uses a specific set of tools, including a bend die, clamp die, pressure die, and sometimes a mandrel and wiper die, to control the material’s tensile and compressive stresses, preventing collapse on the inner surface and cracking on the outer surface
Rotary drill – It is a machine which drills holes by rotating a rigid, tubular string of drill rods to which is attached a bit. It is normally used for drilling large-diameter blastholes in open-pit mines.
Rotary drum feeders – It is simple and sturdy feeder which is suitable for free flowing and small lump bulk materials. It extracts the material from the storage unit. The discharge is positive volumetric and accurate. This feeder is not suitable for very abrasive materials in continuous duty application. It is also not suitable for sticky materials. The material rubs continuously with rotating periphery. This feeder can be considered as an extremely short belt feeder. The drum prevents the bulk material from flowing out but discharges it by rotation. This feeder is only suitable for materials with good flowability which are not prone to aeration.
Rotary dryer – It is an industrial dryer which uses a rotating cylinder (or drum) to reduce moisture content in materials by bringing them into contact with heated gas. Rotary dryers are designed to efficiently dry a variety of materials, including powders, granules, and bulk solids, by exposing them to heated air or gas within a rotating cylindrical shell.
Rotary encoder – It is a transducer which converts rotation of a shaft to a measurement.
Rotary forging – It is a process in which the work-piece is pressed between a flat anvil and a swiveling (rocking) die with a conical working face, with the platens move toward each other during forging. It is also called orbital forging.
Rotary furnace – It is a circular furnace constructed so that the hearth and workpieces rotate around the axis of the furnace during heating. It is also called rotary hearth furnace.
Rotary hearth furnace (RHF) – It is a type of furnace which is used for various high-temperature industrial processes, particularly in the steel industry. It is very useful for several purposes. Besides being utilized for the heating of circular loads (for example in the pipe rolling mills), the rotary hearth furnaces are also being used for the reduction processes. It is designed to heat and process materials such as iron ore, carbon-based materials, and other metallic and non-metallic substances. The basic structure of a rotary hearth furnace consists of a circular hearth or platform that rotates on a set of wheels or rollers. The hearth is typically made of refractory materials that can withstand high temperatures. The furnace chamber is enclosed and heated using burners or other heat sources.
Rotary kiln – It is an inclined, rotating cylindrical reactor through which a charge moves continuously.The rotary kiln is used when thermal processing of solids which is more severe than drying is needed. The furnace walls (normally lined) make intermittent contact with the flue gas and the charge. Heat needed for the various physical and chemical processes is delivered to the charge by lifting and overturning the charge as it moves through the interior of the rotary kiln. The rotary kiln consists of a lined hollow cylinder, mounted in an inclined position on rolls and rotated slowly by a drive. The charge material moves from the feed end to the discharge end because of the rotary motion and gravity. The inclination is between 1.5 % and 5 %. Speed is between 0.2 revolutions per minute and 2 revolutions per minute. Variable-speed drives are normally used to control the residence. Kiln diameter is normally constant over the full length. Some rotary kilns have internals such as conveying or lifting flights, built in crossed-hanging link chains, or ring dams. In some processes, air-feed pipes or burner tubes for gas or oil are installed on the furnace shell. Air or other gases can also be introduced through ports in the lining. Rotary kiln carries out several functions simultaneously. It is equipment for conveying, mixing, heat transfer, and reaction. These functions are to be in harmony. The most widespread usage of rotary kiln is in the production of cement clinker, limestone calcining, production of calcined and dead burnt dolomite, calcined magnesite, and iron ore reduction for the production of direct reduced iron (DRI) etc.
Rotary-kiln gasifier – It is a cylindrical, inclined, and rotating reactor which converts solid fuel or waste into syngas through high-temperature thermal processes. s an engineered system where a rotating, inclined cylindrical drum slowly rotates a solid fuel or waste feedstock, which then undergoes thermal decomposition under controlled conditions to produce syngas (synthesis gas). This process transforms the feedstock into a combustible gas by drying, pyrolyzing, and then reacting it with an oxidant at high temperatures, making it a versatile technology for waste-to-energy applications and fuel production.
Rotary-kiln incinerator – It is a two-chamber furnace with a rotating, slightly inclined cylindrical shell designed to burn solid waste, sludges, and pastes at high temperatures (up to 1,200 deg C to 1,500 deg C). The rotation of the kiln moves the waste through the primary chamber for volatilization and partial combustion, while a secondary chamber completes the gas-phase combustion in excess air, converting waste into a smaller volume of ash (slag) and flue gases.
Rotary kiln process – Rotary kiln carries out several functions simultaneously. It is a device for conveying, mixing, heat transfer, and reaction. These functions are needed to be in harmony. The charge in the kiln moves both radially and axially. Radial motion is determined by the degree of filling (percentage of cross-sectional area occupied by the charge) and the rotational speed. The angle of repose and the kiln inclination govern axial motion. The interior of the charge tends to have a higher bulk density than the exterior, and grain size increases toward the outside. This tendency can be counteracted by the internals, which also improve heat transfer into the charge. Dust production can be limited by pelletizing the feed. Heat transfer occurs principally from the combustion gas (generated by a burner usually installed at the discharge end of the kiln) to the charge. The driving force is normally the temperature difference. The gas can move co-current or counter-current to the longitudinal motion of the charge. Co-current gas flow is advantageous only when the charge temperature does not have to exceed a certain value. The counter-current arrangement is preferred. The different types of heat transfer in a rotary kiln are (i) heat transfer to material by gas radiation and convection, (ii) heat transfer to material by brick radiation, (iii) conductive heat transfer to material from brick, and (iv) heat transfer to brick by radiation, convection, and (v) heat loss by shell radiation and convection.
Rotary kiln sizing and design – Every material is different in terms of how it behaves in the kiln and at what temperatures different reactions are going to occur. When designing a process around a rotary kiln, as well as in the design of the kiln itself, the material is required to undergo thorough chemical and thermal analyses. Various material characteristics play a part in how the material is going to perform in the kiln, and subsequently, how the kiln is to be designed around the material to accomplish the process goal. The following provides an overview of some of the normal material characteristics which can influence the design of the kiln.
Rotary kiln tyre – It is also known as the kiln ring tyre or riding ring. It is a circular steel ring which is sleeved on the rotary kiln cylinder and fixed by the baffle plate and the splint. As an important rotary kiln part, the use of the kiln tyre can effectively transfer the weight of the rotary part of the rotary kiln to the supporting roller part of the rotary kiln. The supporting rollers and other bearing supports carry the full weight of the rotating part. The kiln ring tyre mainly bears three kinds of forces during the operation of the kiln body, temperature difference stress, bending stress and contact stress. If these stresses are too large, the ring tyre is going to be damaged or even broken. When the rotary kiln is running, the cylinder drives the kiln riding ring to rotate, and the kiln riding ring and the supporting roller produces friction, which causes the riding ring to wear to a certain extent. Hence, the material selection and casting of the kiln ring tyre need to have a certain degree of wear resistance.
Rotary lobe pump – It is also called lobe pump. It is a type of positive displacement pump. It is similar to a gear pump except the lobes are designed to almost meet, rather than touch and turn each other. An early example of a lobe pump is the roots blower to blow combustion air to melt iron in blast furnaces, but now more commonly used as an engine supercharger.
Rotary motion – It is also known as rotational or circular motion. It is the movement of an object around a fixed point or axis.
Rotary motion valve – It is the valve in which the valve-closure member travels along an angular or circular path, such as in butterfly, ball, plug, eccentric- and swing check valve.
Rotary oil burner – It is a burner in which atomization is accomplished by feeding oil to the inside of a rapidly rotating cup.
Rotary plough feeders – These feeders are normally of is travelling type. They extract material from storing unit shelf. The feeder travel and thereby storage unit outlet length can be up to 200 meters or so. This feeder is suitable to operate in tunnel under stockpile. The feeder along with civil work is an expensive proposition, and is used to reclaim material from track hopper or long stockpile on storage-yard. The feeder can deal with practically any bulk material, and in large capacity range. The feeder requirement in a particular layout arrangement is without alternative option of matching performance. Thus, this feeder does not compete with other feeders, but competes with the reclaiming machines. It is more as reclaiming machine-cum-feeder. The feeder extracts the material forcefully and so, it can also deal with bulk materials, which have tendency to pack or interlock. The typical capacity range is up to 1250 cubic meters per hour. More capacity is also possible. In general, this is used for lump size up to 450 millimeters. This depends upon the characteristics of the bulk material.
Rotary positive-displacement pumps – These pumps move fluid using a rotating mechanism which creates a vacuum that captures and draws in the liquid. These pumps are very efficient since they can handle highly viscous fluids with higher flow rates as viscosity increases. These pumps fall into five main types namely gear pump, screw pump, rotary vane pump, hollow disc pump, and peristaltic pump.
Rotary pump – It is a type of positive displacement pump that uses rotating parts, like vanes, gears, or lobes, to move a fixed volume of fluid with each revolution, resulting in a continuous, non-pulsating flow. Rotary pumps use mechanical devices such as pistons, gears, or screws to discharge a commodity at a smooth, continuous rate of flow. Seven types of rotary pumps include sliding vane, axial piston, flexible member, lobe, gear, circumferential piston, and screw type rotary pump.
Rotary press – It is a machine for forming powder metallurgy parts which is fitted with a rotating table carrying multiple die assemblies in which powder is compacted.
Rotary regenerator – it is also known as heat wheel. Rotary regenerator is similar to fixed regenerator since the heat transfer is facilitated by storing heat in a porous media, and by alternating the flow of hot and cold gases through the regenerator. Rotary regenerators, sometimes referred to as air preheaters and heat wheels, use a rotating porous disc placed across two parallel ducts, one containing the hot waste gas, the other containing cold gas. The disc, composed of a high heat capacity material, rotates between the two ducts and transfers heat from the hot gas duct to the cold gas duct. Heat wheels are generally restricted to low and medium temperature applications due to the thermal stress created by high temperatures. Large temperature differences between the two ducts sometimes lead to differential expansion and large deformations, compromising the integrity of duct wheel air seals. In some cases, ceramic wheels are used for higher temperature applications. Another issue with heat wheels is preventing cross contamination between the two gas streams, as contaminants can be transported in the wheel’s porous material.
Rotary retort furnace – It is a continuous-type furnace in which the work advances by means of an internal spiral, which gives good control of the retention time within the heated chamber.
Rotary roughening – It is a method of surface roughening prior to thermal spraying wherein a revolving roughening tool is pressed against the surface being prepared, while either the work, or the tool, or both, move.
Rotary seal – It is a mechanical seal which rotates with a shaft and which is used with a stationary mating ring.
Rotary shear -It is a sheet metal cutting machine with two rotating-disk cutters mounted on parallel shafts driven in unison.
Rotary stem – This type of stem is a normally used stem model in ball, plug, and butterfly valves. A quarter-turn motion of the stem open or close the valve.
Rotary swager – It is a swaging machine consisting of a power-driven ring which revolves at high speed, causing rollers to engage cam surfaces and force the dies to deliver hammer-like blows on the work at high frequency. Both straight and tapered sections can be produced.
Rotary swaging – It is a bulk forming process for reducing the cross-sectional area or otherwise changing the shape of bars, tubes, or wires by repeated radial blows with one or more pairs of opposed dies.
Rotary switch – It is a switch which is operated manually or electrically with a rotary motion of the contacts.
Rotary table feeders – These feeders are normally used for the volumetric feeding of fine bulk materials solids which have reasonably good flowability. They are suitable to install under storage unit outlet of larger diameter to prevent clogging by the sluggish material. The feeders are suitable for nonabrasive and marginally abrasive bulk materials. The material continuously rubs / slides on the table. However, table can be fitted with thick liner if needed. Discharge is volumetric in nature. The capacity range is normally less than 20 cubic meters per hour. The rotary table feeder can be considered as an inverse of the plough feeder.
Rotary table furnace – It is also known as rotating hearth furnace. In this furnace, materials are placed on the merry-go-round-like hearth. The materials travel on a circular track and undergo reduction reactions / heating while travelling. The reduced product / heated material is later removed after the materials have completed almost a whole revolution. The furnace has several zones.
Rotary transformer – It is a transformer which is used to couple electric signals or power between rotating parts.
Rotary tube piercing (RTP) – It is also known as the Mannesmann process. It is a hot-working metal-working process used to manufacture seamless tubes by forcing a heated cylindrical billet through a rotating piercer, creating a hollow shell.
Rotary valves – These valves use rotational motion to turn a closure member into and out of a seating surface.
Rotary vane feeders – These feeders can be considered as an extremely short apron feeder. They are particularly used to discharge fine freely flowing bulk materials from the storage units, while maintaining sealing so that air / gases do not flow into storage unit when the storage unit is under negative air pressure. These feeders are regular features for discharge of dust from dust collection hopper / enclosure in a dust extraction plant. These feeders can also be used when such sealing is not needed. The discharge is positive volumetric in nature. The other area of application can be process-plant, where material is to flow in a totally enclosed construction. The feeder is suitable for materials which are free-flowing and non-sticky. This feeder application competes with screw feeder, but is not as popular as screw feeder. However, if feeding is to be accomplished with minimum horizontal displacement, then this feeder is the choice.
Rotary vane pump – It is a type of positive displacement pump which uses sliding vanes mounted on an eccentrically placed rotor to trap and compress a fluid, creating a vacuum or moving liquids. As the rotor turns inside a stator, centrifugal force pushes the vanes outward, creating expanding chambers which draw in the fluid. These chambers then shrink, compressing and expelling the fluid through an outlet. Rotary vane pumps are known for their simple, robust design, self-priming capabilities, and suitability for several applications in industries.
Rotary variable differential transformer – It is a transformer-like transducer which measures rotation as an analog value.
Rotating biological process– It is a fixed film aerobic process similar to the trickling filter process except that the media is supported horizontally across the tank of the waste-water. The media upon which the bacteria grow is continuously rotated so that it is alternately in the waste-water and the air.
Rotating electrical machine – It is an electro-mechanical device which converts energy between electrical and mechanical forms by utilizing a rotating, moving part called a rotor. These devices function as either a motor (converting electrical to mechanical energy) or a generator (converting mechanical to electrical energy). They consist of a stationary part (stator) and a rotating part (rotor), with magnetic fields generated by electrical currents interacting to produce torque or induce voltage.
Rotating electrode powder – It is an atomized powder consisting exclusively of solid spherical or near spherical particles.
Rotating electrode process (REP) – In this process, a bar of the desired composition, 15 millimeters to 75 millimeters in diameter, serves as a consumable electrode. The face of this positive electrode, which is rotated at high speed, is melted by a direct current electric arc between the consumable electrode and a stationary tungsten negative electrode. The process is carried out in helium. Centrifugal force causes spherical molten droplets to fly off the rotating electrode. These droplets freeze and are collected at the bottom of the tank, which is filled with helium or argon. A major advantage of this process is the elimination of ceramic inclusions and the lack of any increase in the gas content of the power relative to the alloy electrode.
Rotating equipment loads – Typical heavy rotating equipments include centrifugal air and gas compressors, horizontal and vertical fluid pumps, generators, rotating steam and gas turbine drivers, centrifuges, electric motor drivers, fans, and blowers. These types of equipments are characterized by the rotating motion of one or more impellers or rotors. The rotating equipment loads are (i) dynamic loads because of unbalanced masses, (ii) design levels of unbalance and basis (this information documents the unbalance level the subsequent transmitted forces are based on), (iii) equipment unbalance provided by the manufacturer, (iv) equipment unbalance meeting industry criteria, (v) equipment unbalance determined from trip vibration level and effective bearing stiffness(vi) dynamic load determined from an empirical formula, and (vii) loads from multiple rotating equipments.
Rotating influent distributor – It is normally used in trickling filters for waste-water treatment. It is a mechanism which evenly distributes waste-water across the filter media bed by rotating arms with orifices or spreaders.
Rotating membrane – It is a dynamic filtration or emulsification system where a membrane component rotates, typically on an axis, to improve performance by increasing shear forces between the membrane and the fluid. This rotation generates high shear to reduce membrane fouling by dislodging deposits and improving mass transfer, leading to higher filtration flux or creating fine, uniform droplets in emulsification processes.
Rotating mould – It is the key component in the rotational molding (or roto-moulding) process, a method for producing large, seamless, hollow plastic objects by rotating a heated mould on two perpendicular axes while a polymer material is dispersed and adheres to the mould’s internal surfaces, resulting in a part with uniform wall thickness. The rotating mould serves as the cavity for the plastic, and its continuous rotation ensures that gravity causes the softened material to coat the interior walls, creating a hollow shape.
Rotating reactor – It is a device which utilizes mechanical rotation to improve mixing, heat, and mass transfer for chemical and biological reactions, involving one or more rotating components such as impellers, discs, or packed beds. Different types exist, including rotary kilns for high-temperature gas-solid reactions, spinning disc reactors (SDRs) for fast reactions and high heat / mass transfer, and rotating bed reactors (RBRs) for efficient contact between fluids and solid catalysts. These reactors are vital in different industries, from chemical and metallurgical processes to biocatalysis, where they offer benefits like intense mixing, improved efficiency, and the ability to handle high solid-to-liquid ratios.
Rotating screen effect – The interlaced toothed rotor design of mineral sizers allows free flowing undersize material to pass through the continuously changing gaps generated by the relatively slow-moving shafts.
Rotating shears – These shears have the leading-edge technology and are used when high speed and accuracy are required. This is achieved by an optimized combination of motion control strategies aiming to get the best performance with the minimum effort from the machine. Fast dynamic motion applied to rotating blades and the diverter are necessary to deliver highly versatile and accurate rotating shears, capable of doing head and tail crops, scrapping and cut-to-measure at a speed of up to 100 meters per second. A peculiarity of rotating shears is the synergy between a high inertia system (the shear blades) and a low inertia system (the diverter). The big challenge for upgrades is to use the same motion control system for both parts, optimizing it for the two different tasks.
Rotating wheel test – It is also known as a rotating wheel dip test (RWDT). It is a method used to assess the tracking and erosion resistance of composite insulator housing materials by subjecting them to artificial harsh environments and electrical stress.
Rotation – It is the circular movement of an object around a fixed central point or line, known as an axis of rotation. This motion can be a spin around an internal axis, like a crankshaft, or a revolution around an external axis, such as earth orbiting the sun. Engineers analyze rotational motion to understand and design systems involving rotating components, considering factors like angular momentum, forces, and the specific geometry of motion.
Rotational acceleration – It is the rate of change of rotational velocity. It has dimension of squared reciprocal time and SI (International System of Units) units of squared reciprocal seconds. Hence, it is a normalized version of angular acceleration and it is analogous to chirpyness.
Rotational axis – It is an imaginary line around which an object rotates, with all points on the axis remaining stationary. This fundamental concept describes the motion of rotating components like wheels, gears, and the rotors in electric motors, where the axis defines the direction and speed of the spin. Understanding the rotation axis is critical for analyzing an object’s dynamic behaviour, balancing, stability, and the effectiveness of rotational forces.
Rotational casting – It is a method which is used to make hollow articles from thermoplastic materials. The material is charged into a hollow mould capable of being rotated in one or two planes. The hot mould fuses the material into a gel after the rotation has caused it to cover all surfaces. The mould is then chilled, and the product is stripped out..
Rotational energy – It is also called angular kinetic energy. It is the kinetic energy because of the rotation of an object and is part of its total kinetic energy. Looking at rotational energy separately around an object’s axis of rotation, the dependence on the object’s moment of inertia which is observed is Erotational = 1/2 I x w square, Erotational=12Iω2where ‘w’ ω is the angular velocity, ‘I’ I is the moment of inertia around the axis of rotation, and ‘E’ E is the kinetic energy. The mechanical work needed for or applied during rotation is the torque times the rotation angle. The instantaneous power of an angularly accelerating body is the torque times the angular velocity. For free-floating (unattached) objects, the axis of rotation is normally around its centre of mass. There exists close relationship between the result for rotational energy and the energy held by linear (or translational) motion Etranslational = 1/2 m x v square. Etranslational=12mv2In the rotating system, the moment of inertia ‘I’ takes the role of the mass ‘m’, and the angular velocity ‘w’ω, takes the role of the linear velocity ‘v’. The rotational energy of a rolling cylinder varies from one half of the translational energy (if it is massive) to the same as the translational energy (if it is hollow).
Rotational frequency – It is also known as rotational speed or rate of rotation. It is the frequency of rotation of an object around an axis. Its SI (International System of Units) unit is the reciprocal seconds (per second). Other common units of measurement include the hertz (Hz), cycles per second (cps), and revolutions per minute (rpm).
Rotational kinetic energy – It is the energy an object possesses because of its spinning motion around an axis. This rotational energy is equal to the multiplication of value of the moment of inertia (a measure of resistance to rotational changes in motion) and the square of the angular velocity. This concept is important for understanding the dynamics of rotating machinery and systems, such as gears, flywheels, and turbines, since it directly relates to the work needed to start, stop, or change the speed of these components.
Rotational moulding – This process is normally applied to the plastics. It involves a heated mould which is filled with a charge or shot weight of the material. It is then slowly rotated (normally around two perpendicular axes), causing the softened material to disperse and stick to the walls of the mould forming a hollow part. In order to form an even thickness throughout the part, the mould rotates at all times during the heating phase, and then continues to rotate during the cooling phase to avoid sagging or deformation. It is the preferred term for a variation of the rotational casting process which uses dry, finely divided (35 mesh, or 500 micrometers) plastic powders, such as polyethylene, rather than fluid materials. After the powders are heated, they are fused against the mold walls forming a hollow item with uniform wall thickness.
Rotational motion– It is the movement of a rigid body around a fixed axis, where every point on the body traces a circular path centered on that axis. It is distinct from linear motion and is described by concepts like angular displacement, angular velocity, and angular acceleration, with torque being the force which causes it. Understanding rotational motion is crucial for designing and analyzing rotating machinery, from simple wheels and gears to complex robotic arms.
Rotational movement – It is the motion of an object around a fixed axis or point, where every particle in the object travels in a circular path. This motion is described using angular quantities like angular velocity (rate of rotation) and angular acceleration (rate of change in rotation), and is fundamentally different from linear motion. Understanding rotational motion is vital for analyzing and designing machines, from turbines and gears to robotic arms, as it involves concepts like torque (the force causing rotation) and moment of inertia (resistance to rotational change).
Rotational speed, fan – Rotational speed of a fan is typically measured in revolutions per minute (rpm). Fan rotational speed has a considerable impact on fan performance. Rotational speed is to be considered alongside with other issues, such as variation in the fan load, air stream temperature, ambient noise, and mechanical strength of the fan. Variations and uncertainties in system requirements are critical to fan type and fan rotational speed selection. Fans which generate high air flow at relatively low speeds (for example, forward-curved blade centrifugal fans) need a relatively accurate estimate of the system air flow and pressure demand.
Rotational velocity – It is the vector quantity whose magnitude equals the scalar rotational speed. In the special cases of spin (around an axis internal to the body) and revolution (external axis), the rotation speed can be called spin speed and revolution speed respectively.
Rotodynamic pump – It is a kinetic machine which uses a rotating element, like an impeller, to continuously impart mechanical energy to a fluid, converting it into kinetic energy (velocity) and then, through pressure conversion, into stored energy (pressure). Unlike positive displacement pumps which trap fixed fluid volumes, rotodynamic pumps, such as centrifugal, mixed flow, and axial flow types, provide a continuous flow of fluid by dynamically increasing its velocity.
Rotor – It is that part of an electrical machine that rotates. It is not necessarily the armature.
Rotor blade – It is an airfoil-shaped component which rotates on a central axis to generate lift, create thrust, or convert kinetic energy into mechanical work. These blades are important for devices like wind turbines, where they capture wind energy to generate electricity.
Rotor dynamics – It is a specialized branch of applied mechanics concerned with the behaviour and diagnosis of rotating structures. It is normally used to analyze the behaviour of structures such as jet engines and steam turbines. At its most basic level, rotor dynamics is concerned with one or more mechanical structures (rotors) supported by bearings and influenced by internal phenomena which rotate around a single axis. The supporting structure is called a stator. As the speed of rotation increases the amplitude of vibration frequently passes through a maximum which is called a critical speed. This amplitude is normally excited by imbalance of the rotating structure. If the amplitude of vibration at these critical speeds is excessive, then catastrophic failure occurs. In addition to this, turbo-machinery frequently develop instabilities which are related to the internal makeup of turbomachinery, and which is to be corrected. This is the main concern of engineers who design large rotors.
Rotor imbalance – In rotating machinery, rotor imbalance refers to an uneven distribution of mass around the axis of rotation, causing the rotor to vibrate and experience excessive forces during operation.
Rotor pole – It is a distinct magnetic pole on the rotating part (rotor) of an electric motor or generator. These poles, which are magnetic field-generating components, create the rotating magnetic field which interacts with the stationary stator, producing torque or power. Rotor poles can be ‘salient’ (projecting outwards, like on a salient pole rotor) or part of a smooth, cylindrical rotor, and their design influences the machine’s characteristics.
Rotor torque – It refers to the torque generated by the internal electrical-to-mechanical power conversion within a rotor. This torque is the rotational effect of forces acting on the rotor, produced by the interaction of the rotor’s magnetic field with the magnetic field from the stator. It is a key factor in driving the rotor’s rotation and is influenced by rotor current, magnetic flux, and the motor’s power factor.
Rouge finish – It is a highly reflective finish produced with rouge (finely divided, hydrated iron oxide) or other very fine abrasive, similar in appearance to the bright polish or mirror finish on sterling silver utensils.
Rough blank – It is a blank for a metal-forming or drawing operation, normally of irregular outline, with necessary stock allowance for process metal, which is trimmed after forming or drawing to the desired size.
Rough grinding – It consists of grinding without regard to finish, It is normally to be followed by a subsequent operation.
Roughing – It is the initial evacuation of a vacuum system.
Roughing line – It is a line running from a mechanical pump to a vacuum chamber through which preliminary pumping is conducted in the rough vacuum range.
Roughing mill – It is a rolling mill which is used to reduce the thickness of ingots into blooms, billets, or slabs. It is also a rolling mill which is used to reduce the thickness of blooms into billets.
Roughing pump – It is a vacuum pump used for the initial evacuation of a vacuum system.
Roughing stand – It is the first stand (or several stands) of rolls through which a reheated billet / bloom / slab passes in front of the finishing stands.
Rough machining – It is the machining without regard to finish. It is normally to be followed by a subsequent operation.
Roughness – It consists of relatively finely spaced surface irregularities, the heights, widths, and directions of which establish the predominant surface pattern. It is also the microscopic peak-to-valley distances of surface protuberances and depressions.
Rough order of magnitude (ROM) – Rough order of magnitude estimate is a preliminary, approximate cost estimate used in the early stages of project planning when detailed information is scarce, providing a general idea of potential costs for initial decision-making.
Rough-polishing process – It is a polishing process which is having the primary objective of removing the layer of significant damage produced during earlier machining and abrasion stages of a metallographic preparation sequence. Its secondary objective is to produce a finish of such quality which a final polish can be produced easily.
Rough surface – It is one with microscopic irregularities like peaks and valleys which deviate from a perfectly smooth ideal surface, a characteristic that influences functional properties such as friction, fluid flow, and thermal properties. The degree of roughness, quantified by parameters like average roughness (Ra), is controlled by manufacturing processes and is critical for a component’s performance, durability, and interaction with its environment.
Rough top conveyor belt – The uneven cover rubber surface of this conveyor belt prevents slippage while preventing vibration of, or absorbing and reducing impact to transport materials by providing a cushion effect. This belt is ideal for transporting plywood or packed items.
Round blooms – These are the semi-finished products normally used in the manufacture of seamless pipes. The diameter of these rounds is equal to higher than 180 millimeters.
Round-bottom flasks – These are types of flasks having spherical bottoms used as laboratory glassware. They are typically made of glass for chemical inertness. In modern days, they are normally made of heat-resistant boro-silicate glass. There is at least one tubular section known as the neck with an opening at the tip. Two-necked or three-necked flasks are common as well.
Round flame – It refers to a flame shape which is normally circular or spherical, frequently produced by burners designed to direct the flame towards the centre or a specific area, as opposed to a flat or rectangular flame.
Rounding – It is also called rounding off. It is the process of adjusting a number to an approximate, more convenient value, frequently with a shorter or simpler representation. Rounding is frequently done to get a value which is easier to report and communicate than the original. Rounding can also be important to avoid misleadingly precise reporting of a computed number, measurement. Rounding of exact numbers will introduce some round-off error in the reported result.
Round lifting magnet – It is built with a centre pole (or core) and a round outer pole concentric with the centre pole. This magnet can be either a permanent magnet or an electro-magnet. The round electro lifting magnet is the most efficient when considering its face area as related to the lift power. Since the outer pole is a consistent distance from the core or centre pole, the result is a uniform magnetic strength over the magnet face area. Black iron pipe or steel tubing is used for outer poles of round lifting magnets, and hot rolled steel round bar stock is used for the centre core of round electro magnets.
Roundness – It defines the perfect condition where all points on a surface are equidistant from a common centre point, a concept used for features like discs, spheres, and cylinders. Roundness is typically specified in a 2D cross-section and is quantified by the separation of two concentric circles which contain the measured profile. Deviations from this ideal condition, called errors of roundness or out of roundness, can manifest as ovality, lobing, or other irregularities, which are to be within a specified tolerance for functional parts to operate correctly.
Round-off error – It is the difference between the exact mathematical value of a number and its approximate representation, which occurs since computers and calculators use a finite number of digits to store and process real numbers. This finite precision limits a system’s ability to represent certain real numbers precisely, leading to small inaccuracies in calculations which can accumulate and considerably affect the final results of engineering simulations and analyses, especially in complex or iterative processes.
Routh–Hurwitz stability criterion – It is a criterion for predicting the stability of a system with a given transfer function.
Routine maintenance – It includes those maintenance activities which are repetitive and periodic in nature. It involves regularly scheduled, proactive tasks like inspections, cleaning, lubrication, and minor repairs to keep equipment, systems, and infrastructure in optimal working order.
Router – It is a hardware device which connects two or more networks, or sub-networks, and forwards data packets between them based on their destination IP (Internet Protocol) addresses to ensure they reach the correct destination. Operating at the network layer (Layer 3) of the OSI (Open Systems Inter-connection) model, a router uses a routing table to determine the most efficient path for data to travel, enabling multiple devices to share an internet connection and forming the backbone of both local (LAN) and wide area networks (WANs)
Routing – It refers to the sequence of operations and processes needed to transform raw materials or components into a finished product. It outlines the specific steps, work centres, machines, and resources needed for each operation in the production process.
Roving – It means a number of yarns, strands, tows, or ends collected into a parallel bundle with little or no twist.
Roving ball – It is the supply package offered to the winder, consisting of a number of ends or strands wound to a given outside diameter onto a length of cardboard tube. It is normally designated by either fibre weight or length in yards.
Roving cloth – It is a textile fabric, coarse in nature, woven from rovings.
Royalty – It is the amount of money paid at regular intervals by the lessee or operator of an exploration or mining property to the owner of the ground. It is normally based on a certain amount per ton or a percentage of the total production or profits. Also, it is the fee paid for the right to use a patented process.
RPM – It is acronym for revolutions per minute. It is a unit of measurement for rotational speed which quantifies the number of complete turns an object makes around its axis in one minute. It is a common metric for the speed of engines, fans, and computer hard drives, with higher revolutions per minute normally indicating faster rotation and, in engines, higher power output.
R-ratio – It is also called R-factor. In cyclic fatigue testing, it is the ratio of applied minimum stress to maximum stress. When ‘R’ = –1, the cycle is equally compressive and tensile.
Rubber – It is defined as an elastic substance, specifically an elastomer, which is a polymer with the ability to stretch and return to its original shape after being deformed, and can be either natural (like poly-isoprene) or synthetic.
Rubber band – It is a tension spring where energy is stored by stretching the material.
Rubber-based adhesive – It is also known as an elastomeric adhesive,, It is a material that uses natural or synthetic rubber as its primary component to bind two surfaces together. These adhesives show high tack and elasticity, allowing them to bond quickly and effectively, especially to porous materials and irregular surfaces. They are versatile, found in everything from tapes and labels to structural applications, and can be formulated as solvent-based, water-based, or hot-melt adhesives.
Rubber boot – It is a protective device to prevent entrance of damaging foreign material into the piston actuator seal bushing.
Rubber compounds – These are complex polymer systems where different solid and liquid ingredients are dispersed in an elastomer matrix, which shows strong viscoelastic properties. These compounds frequently consist of multiple elastomers and reinforcing fillers which interact to create structured materials with unique flow characteristics.
Rubber forming – It is the forming of a sheet metal wherein rubber or another resilient material is used as a functional die part. Processes in which rubber is used only to contain the hydraulic fluid are not classified as rubber forming.
Rubber gasket – It is a flexible, often circular or rectangular, piece of rubber used to create a seal between two mating surfaces, preventing leaks of liquids or gases.
Rubber insulating gloves – These are meant for protecting against electrical shock. These gloves are available to meet different voltage exposures. Lightweight low voltage gloves are for use on voltages under 1,000 volts. Gloves for use on high voltage are of thicker material for the dielectric strength. As the use voltage rating increases so does the glove weight. Rubber gloves are to be visually inspected and an ‘air’ test is to be performed before they are used. Electrical protective equipment is to be subjected to periodic electrical tests. Test voltages and the maximum intervals between tests are to be as per the appropriate standards.
Rubber joining – It is also known as rubber bonding. It is the process of creating a strong and durable connection between rubber and another material (like metal, plastic, or another rubber) using methods like adhesives, vulcanization, or moulding.
Rubber mat – It is a functional product made from different rubber compounds and additives, designed to serve specific purposes such as electrical insulation, anti-fatigue, shock absorption, or providing grip and protection. The material’s specific properties (such as flexibility, durability, chemical resistance, and slip-resistant surface) are engineered and specified for applications in industrial, commercial, and residential settings, where it can protect surfaces and ensure safety.
Rubber matrix – It is the fundamental, flexible polymeric material in a composite, acting as a host for reinforcing fillers or other functional components to improve the overall material’s properties. The rubber matrix provides the material’s elasticity, shape, and ability to hold the reinforcements in place, while the incorporated materials (e.g., such as fibres, silica, or nano-particles) contribute increased strength, stiffness, or specific functionalities like electrical conductivity.
Rubber membrane – It is a flexible, durable sheet of synthetic or natural rubber used as a barrier to control the transport of species, mainly for waterproofing, insulation, or separation in applications like roofing, tank lining, and even certain industrial processes. Key properties include weather resistance, high flexibility, longevity, and chemical resistance, with EPDM (ethylene propylene diene monomer) being a common type known for its durability and ability to withstand extreme temperatures.
Rubber moulding – It is a manufacturing process which transforms raw, uncured rubber into specific, usable shapes by using heat and pressure to force the material into a pre-designed metal mould. This process utilizes different techniques, mainly injection moulding, compression moulding, and transfer moulding, to create a wide variety of durable and resilient rubber products for industries.
Rubber, natural – It consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Types of poly-isoprene which are used as natural rubbers are classified as elastomers. Presently, rubber is harvested mainly in the form of the latex from the Para rubber tree or others. The latex is a sticky, milky and white colloid drawn off by making incisions in the bark and collecting the fluid in vessels in a process called ‘tapping”7’. Manufacturers refine this latex into the rubber that is ready for commercial processing. Natural rubber is used extensively in several applications and products, either alone or in combination with other materials. In majority of its useful forms, it has a large stretch ratio and high resilience and also is buoyant and water-proof.
Rubber-pad forming – It also known as flexible-die forming. It uses a rubber pad or a flexible diaphragm as one tool half, requiring only one solid tool half to form a part to final shape. The solid tool half is normally similar to the punch in a conventional die, but it can be the die cavity. The rubber acts somewhat like hydraulic fluid in exerting nearly equal pressure on all workpiece surfaces as it is pressed around the form block. It is a sheet metal forming operation for shallow parts in which a confined, pliable rubber pad attached to the press slide (ram) is forced by hydraulic pressure to become a mating die for a punch or group of punches placed on the press bed or base-plate. It is also known as the Guerin process. Variations of the Guerin process include the fluid-cell process, fluid forming, and Marforming process.
Rubber reinforcement – It refers to the process of improving the mechanical properties of rubber through the addition of nano-fillers, which improve specific surface area and influence reinforcement efficiency by different mechanisms, including filler interactions and stress transfer at interfaces.
Rubber, synthetic – It is an artificial elastomer. It consists of polymers which are synthesized from petroleum by-products. Synthetic rubber, just like natural rubber, has several uses in the automotive industry for tyres, door and window profiles, seals such as O-rings and gaskets, hoses, belts, matting, and flooring. It offers a different range of physical and chemical properties which can improve the reliability of a given product or application. Synthetic rubbers are superior to natural rubbers in two major respects namely thermal stability, and resistance to oils and related compounds. It is more resistant to oxidizing agents, such as oxygen and ozone which can reduce the life of products like tyres.
Rubber vulcanization – It is a chemical cross-linking process which transforms rubber into a durable, elastic material by adding sulphur (or other compounds) and applying heat. This process creates three-dimensional polymer networks by forming sulphur cross-links between the long-chain molecules of the rubber, resulting in improved properties such as improved elasticity, strength, temperature stability, and resistance to abrasion and solvents.
Rubber waste – It refers to the discarded or end-of-life rubber products, such as tyres, industrial components, and consumer goods, which pose environmental and resource challenges because of their non-biodegradable nature. Waste management engineering focuses on the design and implementation of sustainable processes, like shredding, devulcanization, and recycling, to transform this waste into valuable secondary materials for new products or energy recovery, hence supporting a circular economy.
Rubber wheel – It is a grinding wheel made with a rubber bond.
Rubber wheel abrasion test – It measures a material’s resistance to wear by simulating sliding abrasion conditions using a rotating rubber wheel and dry sand, quantifying wear as volume loss.
Rubbing (polishing) – It is a macro- or microscale fractographic feature resulting from relative movement of two crack faces. It is common in fatigue loading.
Rubbing bearing – It is a bearing in which the relatively moving parts slide without deliberate lubrication.
Rubbing seal – It is a dynamic sealing device which maintains a seal through direct, frictional contact between its sealing element and a rotating or moving component, typically relying on the elasticity of the material and lubrication to dissipate heat and control wear. Examples include lip seals, felt washers, and carbon seals, which prevent leakage of fluids or ingress of contaminants in applications like pumps, engines, and gearboxes.
Rubble – It refers to rough, broken, and irregular fragments of stone, brick, and concrete which are used either as debris from demolished structures or as raw material in construction, especially for fill, foundations, and rubble masonry. It is valued for its strength and durability, though it lacks the uniformity of dressed stone and can be incorporated into walls as a core or in coursed or random designs, sometimes with mortar.
Rubble trench foundation – It is a type of foundation which uses loose stone or rubble to minimize the use of concrete and improve drainage. It is considered more environmentally friendly than other types of foundation since cement manufacturing needs the use of large quantities of energy. However, some soil environments are not suitable for this kind of foundation, particularly expansive or poor load-bearing (less than 0.1 MPa) soils. A rubble trench foundation with a concrete grade beam is not desired for earthquake prone areas.
Rubens tube – It is a demonstration device to visualize acoustic standing waves in a tube by using a row of flames to show the varying pressure and displacement of the sound wave. A pipe filled with flammable gas, such as propane, has small holes along its length, which are ignited to create flames. When sound is played into the tube, the pressure variations cause the flames to become taller or shorter, revealing the pattern of the standing wave and demonstrating the relationship between sound, pressure, and wave-length.
Rube Goldberg machine – It is a chain reaction–type machine or contraption intentionally designed to perform a simple task in an indirect and (impractically) overly complicated way. Normally, these machines consist of a series of simple unrelated devices, The action of each triggers the initiation of the next, eventually resulting in achieving a stated goal.
Rubidium (Rb) – It is a chemical element having atomic number 37. It is a very soft, whitish-grey solid in the alkali metal group, similar to potassium and caesium. It has a density higher than water. Natural rubidium comprises two isotopes namely 72 % is a stable isotope 85Rb, and 28 % is slightly radioactive 87Rb, with a half-life of 48.8 billion years. The colour of its emission spectrum is deep red. Rubidium’s compounds have various chemical and electronic applications. Rubidium metal is easily vapourized and has a convenient spectral absorption range, making it a frequent target for laser manipulation of atoms. Rubidium ions have similar properties and the same charge as potassium ions.
Rub mark – It is a large number of very fine scratches or abrasions. A rub mark can occur by metal-to-metal contact, movement in handling, and movement in transit.
Rub, tool – It is a surface area showing a scratch or abrasion resulting from contact of the hot extrusion with the press equipment or tooling or, in the case of multi-hole dies, with other sections as they exit the press.
Rudder – It is a primary control surface which used to steer a ship, boat, submarine, hovercraft, airship, or other vehicle that moves through a fluid medium (normally air or water).
Ruggedness – It normally refers to the ability of an equipment, component, or a sintered part to withstand harsh conditions, impacts, or stresses without significant deformation or failure, implying a robust and durable component.
Rugged systems – These are hardware which are designed to operate reliably in harsh environments, featuring enhanced durability and resilience to withstand extreme conditions like dust, water, temperature fluctuations, and physical impacts, making them suitable for demanding applications.
Rugosities – These are also known as asperities. These are the small-scale irregularities on a surface. These are the minute imperfections on a seal face or surface of a mating ring that are the result of normal surface finishing processes. Rugosities, their shapes, sizes, and mechanical properties are the basis for developing several theoretical models for friction, lubrication, and wear behaviour.
Rule-based control (RBC) – It is a supervisory control method which utilizes a set of if-then-else rules to determine optimal operating points for systems, normally using on / off and PID (proportional-integral-derivative) controllers. Its effectiveness relies on the expertise of the operator and can struggle with complex objectives as system intricacies increase.
Rule of mixtures – It is a method which is used to estimate the properties of composite materials by combining the properties of their individual components, providing a weighted average of the constituent properties.
Rules of thumb – These are empirical relationships developed from practical experience. In design, these are frequently used to improve ease of manufacture or to relate performance to costs. Rules of thumb can be very useful when employed by an experienced person, but they can easily be misinterpreted or misused by less experienced personnel.
Runaway speed – It is the maximum speed a hydraulic turbine can reach when the load on the connected generator is suddenly removed, and the turbine continues to operate with maximum water flow. This condition, frequently occurring during an emergency like load rejection, causes the turbine to accelerate to a considerably higher speed than its normal operating speed, creating dangerous centrifugal forces for which the turbine components are to be designed to withstand.
Run chart – It is also known as a run-sequence plot. It is a line graph which displays data in a time sequence, allowing users to visualize trends, shifts, or cycles in a process over time. Frequently, the data displayed represent some aspect of the output or performance of a manufacturing or other organizational process. It is hence a form of line chart.
Rundown tank – It is a safety device used in systems with rotating equipment, such as pumps and compressors, to ensure continuous lubrication of the bearings during an emergency shutdown or when the main oil pump fails. It holds a reserve of oil, allowing gravity to provide flow to the bearings until the rotating shaft has safely coasted to a stop, preventing damage to the bearings.
Run-in – In tribology, it is an initial transition process which is occurring in newly established wearing contacts, frequently accompanied by transients in coefficient of friction, wear rate, or both, that are uncharacteristic of the given tribological system’s long-term behaviour. It also means to apply a specified set of initial operating conditions to a tribological system in order to improve its long-term frictional or wear behaviour, or both. The run-in can involve conditions either more severe or less severe than the normal operating conditions of the tribo-system, and can also involve the use of special lubricants and / or surface chemical treatments. In seals, run-in is the period of initial operation during which the seal-lip wear rate is highest and the contact surface is developed.
Run-in roller table – It is the approach roller table to the rolling mill cooling bed. It is normally provided with individually driven horizontal rollers which are gradually inclined to match the incline of the run-in roller table. The approach table is normally designed to operate faster than the finishing speed of the bar being rolled in order to create a gap between the divided materials at the shear prior to entering the brake slide to the cooling bed. The run-in table rollers are also individually driven and inclined at the same angle as the brake slide. The brake slide lifts the cut bar off the run-in table rollers to allow braking of the cut bar under friction before being discharged onto the first notch of the cooling bed. A hydraulic cylinder cushions the cut bar against the brake slides while lowering it for a smoother control. The entry section of the run-in table is equipped with drop down walls to prevent the larger bar from sliding down the brake slide before the previous bar is discharged.
Runner – It is a channel through which molten metal flows from one receptacle to another. It is the portion of the gate assembly of a casting which connects the sprue with the gate(s). It is also the parts of patterns and finished castings corresponding to the portion of the gate assembly. In a blast furnace, runner is the channel in the cast house for directing of liquid products. Hot metal runner is refractory lined and directs hot metal from trough to the hot metal ladle while slag runner directs liquid slag to slag granulation plant, or to slag pot, or to slag pit.
Runner box – It is a distribution box which divides molten metal into several streams before it enters the casting mould cavity. It is the system into which molten metal is introduced.
Runner extension – In a mould, it is that part of a runner which extends beyond the farthest ingate as a blind end. It acts as a dirt trap and is sometimes vented.
Runner mass – It is the refractory material used for preparing of runner before the cast is opened in a blast furnace. It is normally water based.
Runner riser – It is a conventional runner, normally in the horizontal plane, which permits flow of molten metal to the in gate and is large enough to act as a reservoir to feed the casting.
Runner system – It is also called gating. It is the set of channels in a mould through which molten metal travels to the mould cavity. The system normally consists of a vertical section (down-gate or sprue) to the point where it joins the mould cavity (gate) and leading from the mould cavity further vertical channels (risers or feeders). It includes sprues, runners, gates, and risers.
Running accuracy – It is the precision with which a shaft rotates, particularly in applications with stringent demands, such as machine tool spindles, needing high precision rolling bearings to maintain tight tolerances.
Running-in – It is the process by which machine parts improve in conformity, surface topography, and frictional compatibility during the initial stage of use. Chemical processes, including formation of an oxide skin, and metallurgical processes, such as strain hardening, can contribute.
Running maintenance – It includes those maintenance activities which are carried out while the equipment is running and it represents those activities which are performed before the actual preventive maintenance activities take place.
Runoff – It is the flow of water from land to the ocean caused by rainfall which exceeds the soil’s ability to absorb it. It can have both positive and negative impacts, such as damaging infra-structure and vegetation or providing a source of fresh water in arid areas.
Run-of-mine (ROM) – It is a term which is used loosely to describe ore or coal average grade. It describes ore or coal which has been mined but not yet processed. It can also refer to the unsorted product of a mine.
Run-out – It is the unintentional escape of molten metal from a mould, crucible, or furnace. It is also an imperfection in a casting caused by the escape of metal from the mould.
Run out roller table – These are normally chain-driven roller table at the end of the cooling rake. Run out roller table is provided to transport the pack of the bars to the cold shear.
Run-out table (ROT) – It is a conveyor system located after the finishing mill stands in hot strip mill which transports and cools hot-rolled steel strips to achieve a desired temperature and metallurgical structure before coiling. It features individually driven rollers which carry the red-hot strip through an array of water spray headers or jets, which rapidly reduce the strip’s temperature from its high exit temperature to a specific coiling temperature. This controlled cooling process is crucial for determining the final micro-structure and mechanical properties of the steel product.
Run time – It is the total time a machine is scheduled for and actively engaged in production, calculated by subtracting any unplanned stops (like breakdowns) or planned stops (like changeovers) from the planned production time. In the context of software, run time refers to either the moment a programme is executed or the total duration of its execution from start to finish.
Run-to-failure – Run-to-failure is a failure management strategy which allows an equipment item to run until failure occurs and then a repair is done. This maintenance strategy is acceptable only if the risk of a failure is acceptable without any proactive maintenance tasks.
Runway – It consists of the rails, beams, brackets, and framework on which the crane operates.
Runway beam – In the context of overhead cranes, a runway beam is a long, horizontal structural beam which provides the foundation and path for the crane to travel, typically made of steel, and supports the crane and its lifted loads.
Runway height – It is the distance between the grade level and the top of the rail.
Runway length – It is the longitudinal run of the runway rail parallel to the length of the building.
Runway rail – It is the rail which is supported by the runway beams on which the crane travels.
Rupture – It refers to the sudden breaking or bursting of a material or structure under stress. It frequently occurs after a period of creep or under high tensile forces.
Rupture disk – A rupture disk is a safety device which acts like a safety valve to protect against excessive pressure buildup in a system. However, the disk shatters when its maximum pressure is reached and is to be replaced each time it activates.
Rupture load – It is the total force applied to a material which causes it to fail and break, or rupture. It is the maximum force a material can withstand before a discontinuity, such as a crack, forms and propagates, leading to its ultimate separation. This measurement is frequently determined using a tensile testing machine and is crucial for engineering design to understand a material’s breaking point.
Rupture stress – It is the stress at failure. It is also known as breaking stress or fracture stress. Unless otherwise specified, rupture stress is calculated on the basis of original area for axial loading.
Rupture strength – It is the maximum stress a material can withstand before it breaks, and it can refer to a few different types such as modulus of rupture (MOR) for materials in bending, also known as flexural strength, and creep rupture strength for materials under high temperatures and sustained load, which is the stress that causes rupture after a specific time.
Rural area – It is also called countryside. It is a geographical region located outside of cities and towns, characterized by low population density, open spaces, farmland, and natural landscapes like forests, as opposed to the high density and concentrated development of urban areas. The specific criteria for a rural area can vary by country and even by government agency for statistical and administrative purposes, with some definitions focusing on population thresholds, population density, economic activities like agriculture, or administrative governance.
Rust – It is a visible corrosion product. It is applied only to ferrous alloys. It is an iron oxide, which is a normally reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron (III) oxides (Fe2O3.nH2O) and iron (III) oxide-hydroxide [FeO(OH), Fe(OH)], and is typically associated with the corrosion of refined iron.
Rust inhibitors – These are also known as corrosion inhibitors. These are substances which reduce or prevent the oxidation (rusting) of metals by forming a protective barrier or reacting with corrosive elements.
Rust layer – It is the reddish-brown coating formed on iron or steel because of oxidation, a chemical reaction with oxygen and moisture. This flaky, crumbly layer consists mainly of ferric hydroxide and ferric oxide (Fe2O3.xH2O) and is a form of corrosion which degrades the metal’s surface and structure.
Rust-preventive coatings – These are removable coatings which are used to protect the surfaces of iron, steel, coated or galvanized products, and other alloys. Some compounds also protect non-ferrous metals, such as aluminum, brass, and copper. Coatings of these compounds are to be considered temporary, since their function is to protect surfaces during storage, handling, shipping, and fabrication. An additional application can be necessary after parts are fabricated. In some cases, the coating can need to be removed before fabrication or assembly.
Rust-preventive compounds – These are a combination of basic materials, inhibitors, and specialty additives. They vary in physical characteristics, depending on the properties needed and the quantity of protection needed at corrosion sites. A corrosion cell is like a battery, which has a cathode (-), an anode (+), and an electrolyte (liquid in cells). By coating the corrosion sites (anodes and cathodes) on a surface, rust-preventive compounds prevent contact with electrolytes, such as oxygen and moisture-containing materials. A rust-preventive compound can consist of only one or a combination of these four basic parts namely a carrier, a film former, polar materials, and specialty additives. For example, the rust protection offered by film formers such as grease, petroleum jelly, and low-melting-point waxes, can be improved by the addition of a polar material, which has an affinity for steel and attaches to steel surfaces like a magnet.
Rust staining – It is the reaction between exposed inter-metallic layers (specifically the iron portion of the layers) with oxygen, which cause mild red or brown staining.
Ruthenium (Ru) – It is a chemical element having atomic number 44. It is a rare transition metal belonging to the platinum group. Like the other metals of the platinum group, ruthenium is unreactive to most chemicals. Ruthenium is normally found as a minor component of platinum ores. Ruthenium is used in wear-resistant electrical contacts and thick-film resistors. A minor application for ruthenium is in platinum alloys and as a chemical catalyst. A new application of ruthenium is as the capping layer for extreme ultraviolet photomasks.
Rutherford back-scattering spectrometry (RBS) – It is an analytical technique which is used in materials science. Sometimes referred to as high-energy ion scattering (HEIS) spectrometry. Rutherford back-scattering spectrometry is used to determine the structure and composition of materials by measuring the backscattering of a beam of high energy ions (typically protons or alpha particles) impinging on a sample.
Rutherford scattering – It is a general term for the classical elastic scattering of energetic ions by the nuclei of a target material.
Rutile – It is an oxide mineral composed of titanium di-oxide (TiO2), the most common natural form of titanium di-oxide. Rarer polymorphs of titanium di-oxide are known, including anatase, akaogiite, and brookite. Rutile has one of the highest refractive indices at visible wavelengths of any known crystal and also shows a particularly large birefringence and high dispersion. Owing to these properties, it is useful for the manufacture of certain optical elements, especially polarization optics, for longer visible and infrared wave-lengths up to about 4.5 micro-meters. Natural rutile can contain up to 10 % iron and substantial quantities of niobium and tantalum.
Rutile-based flux – It is a type of flux material, normally used in welding electrodes and flux-cored wires, which mainly contains titanium di-oxide (rutile), a mineral known for its ability to create a stable arc, a smooth weld bead, and easily removable slag. This composition makes rutile-based fluxes considered ‘welder-friendly’ and suitable for different welding positions and applications.
Rutile-sodium (EXX12) – When rutile or titanium di-oxide content is relatively high with respect to the other components, the electrode is especially appealing to the welder. Electrodes with this coating have a quiet arc, an easily controlled slag, and a low level of spatter. The weld deposit has a smooth surface and the penetration is less than with the cellulose electrode. The weld metal properties are slightly lower than the cellulosic types. This type of electrode provides a fairly high rate of deposition. It has a relatively low arc voltage, and can be used with alternating current power or with direct current power with electrode negative (straight polarity).
Rutile-potassium (EXX13) – This coating is very similar to the rutile-sodium type, except that potassium is used to provide for arc ionization. This makes it more suitable for welding with alternating current power. It can also be used with direct current power with either polarity. It produces a very quiet, smooth-running arc.
Rutile-iron powder (EXXX4) – This coating on the electrode is very similar to the other rutile coatings, except that iron powder is added. If iron content is 25 % to 40 %, the electrode is EXX14. If iron content is 50 % or more, the electrode is EXX24. With the lower percentage of iron powder, the electrode can be used in all positions. With the higher percentage of iron powder, it can only be used in the flat position or for making horizontal fillet welds. In both cases, the deposition rate is increased, based on the amount of iron powder in the coating.
Rutile phase – It is the tetragonal crystal structure of titanium di-oxide (TiO2) which is the most thermodynamically stable form of the compound under ambient conditions. It features a dense, compact atomic arrangement where titanium atoms are coordinated by six oxygen atoms in octahedra, which are linked to form a three-dimensional framework. Because of its inherent stability and high density, rutile has a higher Mohs hardness and a higher dielectric constant than other polyforms like anatase, making it suitable for applications needing durability and electronic properties.
r-value – It is also called the Lankford coefficient or the plastic strain ratio. It is the plastic strain ratio of sheet metal intended for deep-drawing applications. It is a measure of the resistance to thinning or thickening when subjected to either tensile or compressive forces in the plane of the sheet i.e., it is the ability to maintain thickness as the material is drawn. It is the ratio of the true width strain to the true thickness strain at a particular value of length strain. Strains of 15 % to 20 % are normally used for determining the r-value of low carbon sheet steel. Like n-value, the ratio will change depending on the chosen reference strain value.
R-value – In fatigue testing, it is the stress ratio determined by the minimum stress in the stress cycle divided by the maximum stress. For a completely reversed stress cycle, R = -1.
Rydberg constant – It is a fundamental constant which relates the wave-lengths of spectral lines in hydrogen and serves as a key parameter in the precise determination of other fundamental constants such as the electron mass, charge, and Planck constant.
RZ powder – It is the reduced iron powder made from the scale of pig iron.
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