Glossary of technical terms for the use of metallurgical engineers Terms starting with alphabet ‘V’
Glossary of technical terms for the use of metallurgical engineers
Terms starting with alphabet ‘V’
Vacancy – It is a structural imperfection in which an individual atom site is temporarily unoccupied.
Vacancies – It refers to several lattice sites which are unoccupied. The number of vacancies increases exponentially with temperature. In the equilibrium state, e.g., in an undeformed aluminum crystal at room temperature, around one in every billion lattice sites is unoccupied. In contrast, one in a thousand is unoccupied just below the melting point.
VAC-ESR process – It consists of electro-slag remelting under reduced pressure.
Vacuum – It is a pressure measurement made between total vacuum and normal atmospheric pressure. Vacuum is space devoid of matter. The word means ‘vacant’ or ‘void’. It is a volume empty of matter, sometimes called ‘free-space’. In practice, only partial vacuums are possible. Vacuum is defined as a space with a pressure considerably lower than atmospheric pressure. It is essentially an area where the concentration of gas molecules is reduced, creating a partial or near-complete absence of matter. Achieving and maintaining a vacuum is crucial in several engineering applications, particularly in industries like semiconductor manufacturing, where controlled environments are necessary.
Vacuum annealing – It is annealing carried out at sub-atmospheric pressure.
Vacuum arc degassing (VAD) process – It is a tank degassing process with electrodes added for the purpose of reheating the liquid steel. This is a single unit process in which the ladle sits in a vacuum tank and is stirred by inert gas through porous plug at the bottom with provision for heating through electrodes and alloying additions. After addition of lime to the liquid steel in the ladle, arcing is carried out at a pressure of 250 millimeters mercury to 300 millimeters mercury to raise the temperature and fuse the lime followed by short duration degassing, additions for chemistry adjustment and deep degassing to pressures as low as 1 millimeter mercury. Argon stirring is continued in all the operational steps and the adjustment of flow rate is done for different operations being carried out during the VAD process. The heating rate is around 3 deg C per minute to 4 deg C per minute and during heating the rate of argon flow is kept on the lower side. In this system, under vacuum, carbon-oxygen reaction and carbon-alumina (Al2O3) reaction under the high temperature arc are of great help in achieving low oxygen content without any solid reaction product. Hydrogen levels as low as 1.5 parts per million (ppm) are achieved caused by intense mass transfer by argon and low partial pressure of hydrogen because of dilution of liberated carbon mono-oxide (CO). The main advantage of this process is the high degree of desulphurization as high as 80 % for production of steels with sulphur levels as low as 0.005 %. Vacuum arc degassing is now a widely used process for the production of clean steel.
Vacuum arc double-electrode remelting process – It is a secondary melting process used to produce high-purity, high-quality metal ingots, especially for demanding applications. It involves melting a consumable electrode in a vacuum environment using an electric arc struck between two electrodes. The molten metal then drips into a water-cooled crucible, solidifying into a refined ingot. This process helps eliminate defects like centerline porosity and segregation, resulting in materials with enhanced chemical and mechanical homogeneity.
Vacuum arc refining (VAR) furnaces – These furnaces are normally used for consolidation and refining reactions. The raw material (sponge or scrap) is pressed into an electrode shape, which is used as a consumable electrode in the arc furnace. Normally, direct current is used to provide a stable arc between the consumable electrode and the counter electrode at the bottom of the furnace. After the arc is ignited the electrode starts to melt, volatile elements and entrapped gases are removed through the high temperature and the vacuum conditions. The refined metal drops to the water-cooled copper bottom where it solidifies. Copper is used as the mould material to prevent reactions with refractories. Vacuum arc refining furnaces can also be used with a permanent electrode if the material is fine scrap. This is fed in separately. These furnaces are also used for alloying high-melting metals such as niobium, tantalum, or titanium. Liquid titanium is very reactive, as are molybdenum and zirconium. Hence, these metals are to be melted in a controlled atmosphere or a vacuum. Vacuum arc refining furnaces are hence suitable for melting and / or recycling these highly reactive metals (also possible in electron-beam furnaces). As with electro-slag remelting furnaces, metal sponge and scrap can be mixed and pressed into consumable electrodes and used as such in the VAR furnace. Frequently refining involves several steps to achieve a pure product, this explains the relatively high energy consumption for titanium. Vacuum arc refining is also used to degas certain steel grades during remelting.
Vacuum arc remelting (VAR) – It is a consumable-electrode remelting process in which heat is generated by an electric arc between the electrode and the ingot. The process is performed inside a vacuum chamber. Exposure of the droplets of molten metal to the reduced pressure reduces the quantity of dissolved gas in the metal.
Vacuum-assisted resin transfer moulding (VARTM) – It is a variant of the resin transfer moulding process which uses only vacuum pressure to impregnate the dry preform during cure. The advantages of this process are that since only vacuum pressure is used, the tooling does not have to withstand high pressures, and only single-sided tooling is needed since a vacuum bag arrangement is used on the top side.
Vacuum atmosphere – It refers to a space where the pressure is considerably lower than the surrounding atmospheric pressure. It is essentially a condition where there is a reduced or near absence of matter, including air, resulting in a low-pressure environment. While a perfect vacuum, which is completely devoid of matter, is theoretical, real-world vacuums, such as those used in industry, involve reducing pressure to levels well below atmospheric pressure.
Vacuum atomization – It is a process used to create metal powders by melting metal under vacuum and then breaking it into fine droplets using a high-pressure inert gas, typically argon or nitrogen, before solidification. This process, repeatedly referred to as ‘vacuum induction melting inert gas atomization’ (VIGA), is known for producing high-purity, spherical metal powders.
Vacuum bag moulding – It is a process in which a sheet of flexible transparent material plus bleeder cloth and release film are placed over the lay-up on the mould and sealed at the edges. A vacuum is applied between the sheet and the lay-up. The entrapped air is mechanically worked out of the lay-up and removed by the vacuum, and the part is cured with temperature, pressure, and time. It is also called bag moulding.
Vacuum brazing – It is a non-standard term for different brazing processes which take place in a chamber or retort below atmospheric pressure.
Vacuum capacitor – It is a capacitor using vacuum as its dielectric. It is useful at high voltages or radio frequency.
Vacuum carbon deoxidation – One of the purposes of treating steel in a degassing unit is to lower the dissolved oxygen content of the steel by means of carbon deoxidation before adding aluminum to kill the steel completely. With such a carbon deoxidation practice there are considerable cost savings as a result of the decreased usage of aluminum. Vacuum carbon deoxidation is described by the reaction ‘[C] + [O] = CO (g)’, where the carbon and oxygen are dissolved in the steel bath.
Vacuum carburizing – It is a high-temperature gas carburizing process using furnace pressures between 13 kilopascals and 67 kilopascals during the carburizing portion of the cycle. Steels undergoing this treatment are austenitized in a rough vacuum, carburized in a partial pressure of hydrocarbon gas, diffused in a rough vacuum, and then quenched in either oil or gas.
Vacuum casting – This process is also called counter-gravity casting. It is basically the same process as investment casting, except for the step of filling the mould. In this case, the material is sucked upwards into the mould by a vacuum pump. In this process, the mould is in an inverted position from the normal casting process, and is lowered into the flask with the liquid metal. One advantage of vacuum casting is that by releasing the pressure a short time after the mould is filled, one can release the un-solidified metal back into the flask. This allows the person to create hollow castings. Since the majority of the heat is conducted away from the surface between the mould and the metal, hence the portion of the metal closest to the mould surface always solidifies first and the solid front travels inwards into the cavity. Hence, if the liquid metal is drained in a very short time after the filling, then a person can get a very thin-walled hollow object etc. Vacuum casting is a form of permanent mould casting in which the mould is inserted into liquid metal, vacuum is applied, and metal is drawn up into the cavity.
Vacuum degassing – It is a process which is used to remove dissolved gases from liquids, particularly molten metals, by reducing the pressure in a container, causing the gases to escape. This technique is crucial in various industries to improve material properties and prevent defects caused by trapped gases. In steelmaking, it is an important secondary steelmaking process. It is an advanced steel refining facility which removes oxygen, hydrogen and nitrogen under low pressures (in a vacuum) to produce ultra-low-carbon steel for demanding electrical and automotive applications. It is normally performed in the ladle, the removal of dissolved gases results in cleaner, higher quality, more pure steel. Vacuum degassing processes which are presently being used can be classified into the three types namely (i) stream degassing practice, (ii) circulation degassing practice, and (iii) ladle or tank degassing practice. Degassing can be carried out either by placing ladle containing molten steel under vacuum (non-recirculating system) or by recirculation of molten steel in vacuum (recirculating system). Examples of recirculating systems are RH, RH-OB, RH-KTB, and DH etc. processes and examples of non-recirculating systems are ladle or tank degassers, including VAD (vacuum arc degassing) and VOD (vacuum oxygen decarburization), and stream degassers.
Vacuum degassing-oxygen blowing process – It is a secondary steelmaking process that refines molten steel by removing dissolved gases (primarily hydrogen, nitrogen, and oxygen) and reducing carbon content under vacuum conditions. This process involves applying a vacuum to the molten steel while simultaneously introducing oxygen to facilitate decarburization (removal of carbon). This dual action results in higher quality steel with improved mechanical and physical properties.
Vacuum deposition – It is the deposition of a metal film onto a substrate in a vacuum by metal evaporation techniques.
Vacuum die casting – It is a process where molten metal is injected into a mould (or die) under high pressure, but with the added step of evacuating air and gases from the mould cavity using a vacuum system before injection. This removal of air and other gases reduces porosity and improves the quality and mechanical properties of the cast part.
Vacuum flask – It is also called Dewar flask or thermos. It is a storage vessel consisting of two flasks or other containers, placed one within the other and joined at the neck, and a space in between which is partially evacuated of air, creating a near-vacuum that considerably reduces the transfer of heat between the vessel’s interior and its ambient environment. Vacuum flasks can greatly lengthen the time over which their contents remain warmer or cooler than the ambient environment.
Vacuum forming – It is a simple yet versatile plastic manufacturing process where a heated plastic sheet is shaped over a mould using vacuum pressure. A vacuum is created between the plastic and the mould, drawing the material tightly against the mould’s contours. Once cooled, the plastic retains the mould’s shape, forming a three-dimensional object.
Vacuum furnace – It is a furnace using low atmospheric pressures instead of a protective gas atmosphere like majority of the heat-treating furnaces.
Vacuum hot pressing – It is a method of processing materials (especially metal and ceramic powders) at high temperatures, consolidation pressures, and low atmospheric pressures.
Vacuum impregnation – It is a process used to seal the inherent porosity in sintered metal parts. This is achieved by creating a vacuum to remove air from the pores, then introducing a sealant (like resin or wax) which fills the voids. This process improves the strength, density, and leak-tightness of the parts, making them suitable for applications requiring pressure or fluid containment.
Vacuum induction degassing and pouring (VIDP) – This furnace is a further development of the conventional vacuum induction melting furnace, which offers all the possibilities of metallurgical and process technology. The vacuum induction degassing and pouring furnace design employs a melting and treatment unit which enables the use of different casting techniques. The modular concept allows for connecting it to casting units for ingot casting, horizontal and vertical continuous casting, or powder production. Because of the smaller volume of the vacuum induction degassing and pouring furnace compared to the vacuum induction furnace and considerably lower desorption and leakage rates, it is possible to get very low pressures with lower pumping capacity. The lower part of the furnace can be decoupled and replaced rapidly. Hence, the vacuum induction degassing and pouring furnace enables faster replacement of different furnace vessels with changes of alloy. Melting bath agitation is caused by the induction coil itself, depending on the power input and the installed frequency. However, use of the coil to assist in the bath agitation is basically limited to the meltdown period. Degassing, e.g., is improved by means of good bath agitation. However, this can be done with the induction coil alone only if there is a high-power input and therefore strong bath heating. This high temperature increase is not always metallurgically desirable.
Vacuum induction melting (VIM) – It is a process for remelting and refining metals in which the metal is melted inside a vacuum chamber by induction heating. The metal can be melted in a crucible and then poured into a mould.
Vacuum infusion – It is a resin injection technique, derived from resin transfer moulding, in which the resin injection tank and inlet port are at ambient pressure and the pressure gradient is created by vacuum on the outlet port.
Vacuum lifters – These are equipment which includes one or several suction pads operating by vacuum. They utilize an electric-powered extraction pump and sealed pads to create a vacuum to attach the lifter to an object.
Vacuum melting – It is the melting in a vacuum to prevent contamination from air and to remove gases already dissolved in the metal. The solidification can also be carried out in a vacuum or at low pressure.
Vacuum metallizing – It is a process in which surfaces are thinly coated by exposing them to a metal vapour under vacuum. It involves heating the coating metal to its boiling point in a vacuum chamber, then letting condensation deposit the metal on the substrate’s surface. Resistance heating, electron beam, or plasma heating is used to vaporize the coating metal.
Vacuum moulding – It is also known as vacuum forming or thermo-forming. It is a manufacturing process where a heated plastic sheet is shaped by applying a vacuum to draw it onto a mould. Essentially, a plastic sheet is heated until pliable, then forced against a mould, frequently a single-surface mould, by the suction created by a vacuum. This process is used to create a wide range of products, from packaging to automotive components.
Vacuum nitro-carburizing – It is a sub-atmospheric nitro-carburizing process using a basic atmosphere of 50 % ammonia / 50 % methane, containing controlled oxygen additions of up to 2 %.
Vacuum oxygen de-carburization (VOD) process – It is a tank degassing unit which is additionally equipped with an oxygen blowing lance. This additional supply of oxygen can be used for the production of extra low carbon stainless steel grade (forced decarburization) or for chemical heating of the liquid steel in conjunction with aluminum/silicon additions (vacuum degassing-oxygen blowing, VD-OB process). The vacuum pump is designed accordingly, having a higher capacity in order to cope with the increased off-gas volume. Vacuum oxygen de-carburization process is considered to be an important vacuum process for production of stainless steel. It is mainly suitable for special stainless steels which need the very low value of carbon, nitrogen, and hydrogen levels. In this process, the ladle is placed in vacuum chamber and there is a provision for oxygen lancing through vacuum tight gland and alloying additions. Basically, the process involves preferential oxidation of carbon over chromium leading to minimum losses of chromium. Because of reduced freeboard available in the ladle, the initial carbon content of the liquid steel is to be as low as 1 %. Here, oxygen injection is carried out at 100 millimeters mercury to 250 millimeters mercury. Silicon is oxidized followed by carbon. De-carburization occurs through start of co bubbling determined by initial temperature and silicon content of the liquid steel. Constant rate of de-carburization occurs depending on the oxygen flow rate. The carbon mono-oxide/carbon di-oxide ratio is monitored and at a bath carbon content of 0.08 %, it increases rapidly. Beyond this limiting carbon percentage, de-carburization rate falls independent of oxygen flow rate with simultaneous chromium oxidation. Oxygen lancing is ceased and the vessel pressure is reduced and argon stirring is carried out further to the reaction between the dissolved oxygen and the remaining carbon. It has been reported that through vigorous stirring carbon can be reduced to levels of 0.005 % and total carbon + nitrogen less than 0.015 % are achieved. The refining sequence in general is controlled by combination of variation in oxygen flow rate, the lance tip-bath surface distance, control of vacuum pressure and the argon flow rate. Addition of sufficient quantity of lime and aluminum helps in excellent desulphurization of the liquid steel.
Vacuum pressure swing adsorption (VPSA) process – It is a gas separation process which utilizes differences in the adsorption and desorption characteristics of gas molecules on a solid adsorbent material at different pressure levels, specifically including a vacuum stage for regeneration. It is a cyclic process where a mixture of gases is passed over the adsorbent at a higher pressure, allowing one or more components to be selectively adsorbed while others pass through. The adsorbed components are then removed by lowering the pressure to a vacuum, hence regenerating the adsorbent for the next cycle. In the process, a gas mixture is introduced into a vessel containing an adsorbent material (like activated carbon or a molecular sieve) at a relatively high pressure. Certain components of the gas mixture are preferentially adsorbed by the adsorbent material.
Vacuum pump system – It the driving force for the vacuum degassing processes for liquid steel. For creating vacuum, there are three basic types of vacuum pump systems which can be used. Each has its own advantages and disadvantages. These are (i) steam ejectors with necessary condensation stages, (ii) steam ejectors in combination with water ring pumps, and (iii) dry mechanical pumping systems. Steam jets work on a constant mass flow basis, while water ring vacuum pumps work on a constant volume basis. Used together, an economic break-even point can be reached to take advantage of the best characteristics of each.
Vacuum quenching – It is a heat treatment process where metal parts are rapidly cooled within a vacuum environment to achieve specific metallurgical properties. This process is typically used to improve hardness, wear resistance, and other mechanical characteristics of materials like steel. It involves heating the material to a high temperature in a vacuum, holding it at that temperature, and then rapidly cooling it, frequently with gas or oil, to induce a desired phase transformation.
Vacuum refining – It consists of melting in a vacuum to remove gaseous contaminants from the metal.
Vacuum residue – It is the residue from vacuum distillation of crude oil.
Vacuum riser-less / pressure riser-less casting (VRC / PRC) – It is a metal casting process which uses either vacuum or pressure (or a combination of both) to force molten metal into a mould cavity without the need for a traditional riser (a reservoir of molten metal to compensate for shrinkage during solidification). This technique aims to create high-quality castings with improved density and reduced defects, especially porosity, by eliminating the dependency on risers.
Vacuum sintering – It is the sintering of ceramics or metals at sub-atmospheric pressure such as a technical vacuum or in a high vacuum. It is a heat treatment process in powder metallurgy where powder compacts are heated to a high temperature (below the melting point) in a vacuum environment to fuse the particles together, creating a solid, dense material. This process eliminates air and impurities, leading to improved material properties and controlled densification.
Vacuum sintering furnace – It is a specialized piece of equipment used in manufacturing and materials processing to sinter materials under controlled, low-pressure (vacuum) or inert gas conditions. Sintering is a process which compacts and forms a solid mass of material by heating it without melting it. The vacuum environment helps to prevent oxidation and other reactions with atmospheric gases, allowing for the creation of high-quality, dense materials with specific properties. Vacuum sintering furnaces are designed to create a controlled, oxygen-free environment for the sintering process.
Vacuum swing adsorption (VSA) – It is a non-cryogenic gas separation technology that utilizes adsorbents to separate gas mixtures at near-ambient pressure and temperature. The process involves adsorption of specific gas molecules onto a solid material (adsorbent) at near-ambient pressure, followed by regeneration of the adsorbent through the application of a vacuum. This method is distinct from cryogenic distillation and pressure swing adsorption (PSA) due to its operation at near-ambient pressures and temperatures. The process begins with a gas mixture being passed over an adsorbent material, which selectively binds to certain gas molecules based on their molecular characteristics and affinity for the adsorbent.
Vacuum testing – It is a leak-testing method in which the enclosure / object under examination is evacuated, the tracer gas applied to the outside surface of the enclosure / object and the gas detected after entering it.
Vacuum tube – It is an electron device which relies on flow of electrons through a vacuum or low-pressure gas. It is a valve. It has been the first electronic devices which can amplify.
Vadose zone – It is the zone between land surface and the water table within which the moisture content is less than saturation (except in the capillary fringe) and pressure is less than atmospheric. Soil pore space also typically contains air or other gases. The capillary fringe is included in the vadose zone.
Valence bond theory – It is a theory explaining the chemical bonding within molecules by discussing valencies, the number of chemical bonds formed by an atom.
Valence electron – It is one of the outermost electrons of an atom, which are located in electron shells.
Valency – It means the combining capacity of an element.
Validation – It means confirmation (through the provision of strong, sound, objective evidence) that requirements for a specific intended use or application have been fulfilled (e.g., a trustworthy credential has been presented, or data or information has been formatted in accordance with a defined set of rules, or a specific process has demonstrated that an entity under consideration meets, in all respects, its defined attributes or requirements).
Validity – In data analysis, validity means that the data measure what they are intended to measure.
Value – In data analysis, value defines the attributes of the data. The data are frequently characterized by relatively ‘low value density’. That is, the data received in the original form usually has a low value relative to its volume. However, a high value can be obtained by analyzing large volumes of such data.
Value analysis – In materials selection and design, It is a team problem-solving process. Its objective is to improve the value of a product from the viewpoint of the user (customer). Value analysis is applied to problems as diverse as automobile engines and gall bladder operations. It works whenever a product or process performs a function and costs money. While the method is frequently used to improve on present products, its greatest power is in optimizing a new design.
Value engineering – Value engineering is a systematic application of recognized techniques which (i) identify the function of a product or service, (ii) establish a value for that function, and (iii) provide the necessary function reliably at the least overall cost. The value of a function is defined as the relationship of cost to performance. Hence maximum value = maximum performance / minimum cost. In all cases, the needed function is to be achieved at the lowest possible life cycle cost consistent with requirements and / or performance, maintainability, safety and aesthetics. Value engineering is a management technique which seeks the best functional balance between cost, quality, and performance of a product, project, process, system or service. Value engineering improves the value of goods or services either by increasing the function or reducing the costs.
Value (of a quantity) – The magnitude of a particular quantity normally expressed as a unit of measurement multiplied by a number. Examples are (i) length of a rod – 5.34 meters or 534 centimeters, (ii) mass of a body – 0.152 kilograms or 152 grams, (iii) quantity of substance of a sample of water (H2O) – 0.012 mol or 12 milli mol. It is to be noted that (i) the value of a quantity can be positive, negative, or zero, (ii) the value of a quantity can be expressed in more than one way, (iii) the values of quantities of dimension one are normally expressed as pure numbers, and (iv) a quantity which cannot be expressed as a unit of measurement multiplied by a number can be expressed by reference to a conventional reference scale or to a measurement procedure or both.
Values – Values are the foundation of everything which the organization does, including its vision, mission, and operations. Values allow those working within the organization to agree upon what is considered good, worthy, or meritorious. They allow common goals which offer guidelines for both individual and group behaviour. The values need to be incorporated as the back-bone of the mission statement to highlight how it is being operationalized. They can also be used to help steady the organization in times of uncertainty or to help resolve different issues. Values keep the organization to stay on track. They are guiding principles for how the organization is governed, functions, and behaves. They articulate the key priorities which the organization stands for internally and externally and serve as lenses to help guide both every-day and strategic decisions. Values which work best are authentic to the organization, and are practiced consistently across the organization.
Valve – It is a mechanical device specially designed to control the fluid flow and pressure within a system or process. Valves are designed for a fluid (either liquid or gaseous) application. They are components in piping systems which, in addition to the function of ‘conducting the medium’ (directing, and changing the nominal width), also have the functions of blocking, or regulating the rate of flow and the pressure. Depending on use, different materials are normally used for a valve. Valves carry out any of the several functions which consist of (i) stopping and starting of flow of the fluid, (ii) throttling the quantity of fluid flow, (iii) controlling the fluid flow direction, (iv) regulating the downstream system or process pressure, (v) relieving the over pressure in the system, (vi) regulating the temperature of process fluid, and (vii) controlling the mixing of fluids. Valves can be extremely simple and a low-cost item in a piping system, or they can be extremely complicated and expensive items. They are essential components of a piping system which conveys liquids, gases, vapours, and slurries etc. They are needed to operate under varying operating conditions which can be corrosive, fluids with high temperatures, and fluids carrying dust. Hence, in the design of the piping system, valves probably need more engineering effort than any other component of the piping system.
Valve actuator – The actuator operates the stem and disk assembly. The valve operation of the stem and disk assembly can be done by a manually operated handwheel, manual lever, motor operator, solenoid operator, pneumatic operator, or hydraulic ram. In some designs, the actuator is supported by the bonnet. In other designs, a yoke mounted to the bonnet supports the actuator. Except for certain hydraulically controlled valves, actuators are outside of the pressure boundary.
Valves and fittings – These are essential components in piping and plumbing system. Valves are devices which control the flow of fluids (liquids, gases, etc.) by starting, stopping, throttling, or redirecting it. Fittings are components used to connect pipes, change their direction, size, or branch the system. While valves are technically a type of fitting, their specialized function frequently places them in a separate category.
Valve body – It is sometimes called the shell. It is the primary boundary of a valve. It serves as the main element of a valve assembly since it is the framework which holds all the parts together. The body, the first pressure boundary of a valve, resists fluid pressure loads from connecting piping. It receives inlet and outlet piping through threaded, bolted, or welded joints. The valve-body ends are designed to connect the valve to the piping or equipment nozzle by different types of end connections, such as butt or socket welded, threaded, or flanged. Valve bodies are cast, forged, or fabricated in a variety of forms and each component have a specific function and constructed in a material suitable for that function.
Valve body assembly – It is an assembly of a valve body, bonnet assembly, bottom flange (if used), and trim elements. The trim includes the closure member, which opens, closes, or partially obstructs one or more ports.
Valve bonnet – The cover for the opening in the valve body is the bonnet, and it is the second most important boundary of a pressure valve. Like valve bodies, bonnets are available in several designs and models. In some designs, the body itself is split into two sections which bolt together. Like valve bodies, bonnets vary in design. Some bonnets function simply as valve covers, while others support valve internals and accessories such as the stem, disk, and actuator. During manufacture of the valve, the internal components, such as stem, and disk etc., are put into the body and then the bonnet is attached to hold all the components together inside. The bonnet is cast, or forged of the same material as the body and is connected to the body by a threaded, bolted, or welded joint. In all cases, the attachment of the bonnet to the body is considered a pressure boundary. This means that the weld joint or bolts which connect the bonnet to the body are pressure-retaining parts. Valve bonnets, although a necessity for the majority of the valves, can also represent a cause for concern since bonnets can complicate the manufacture of valves, increase valve size, represent a considerable cost portion of valve cost, and are a source for potential leakage.
Valve disk – The disc is that part of the valve which allows, throttles, or stops the fluid flow, depending on its position. For a valve having a bonnet, the disk is the third primary principal pressure boundary. The disk provides the capability for permitting and prohibiting fluid flow. With the disk closed, full system pressure is applied across the disk if the outlet side is depressurized. For this reason, the disk is a pressure-retaining part. In the case of a plug or a ball valve, the disk is called plug or a ball. The disk is the third most important primary pressure boundary. With the valve closed, full system pressure is applied across the disk, and for this reason, the disk is a pressure related component. Disks are normally forged, and in some designs, hard surfaced to provide good wear properties. A fine surface finish of the seating area of a disk is necessary for good sealing when the valve is closed. Majority of the valves are named, in part, according to the design of their disks.
Valveless pumps – Valveless pumping assists in fluid transport in several engineering systems. In a valveless pumping system, no valves (or physical occlusions) are present to regulate the flow direction. The fluid pumping efficiency of a valveless system, however, is not necessarily lower than that having valve. In fact, many fluid-dynamical systems in nature and engineering more or less rely upon valveless pumping to transport the working fluids therein.
Valve plug – It is a term frequently used to reference the valve closure member in a sliding-stem valve.
Valve seat(s) – The seat or seal rings provide the seating surface for the disk. A valve can have one or more seats. In the case of a globe or a swing-check valve, there is normally one seat, which forms a seal with the disc to stop the flow. In the case of a gate valve, there are two seats, one is on the up-stream side and the other is on the down-stream side. A gate valve disk has two seating surfaces which come in contact with the valve seats to form a seal for stopping the flow. In some designs, the valve body is machined to serve as the seating surface and seal rings are not used. In other designs, forged seal rings are threaded or welded to the body to provide the seating surface. For improving the wear-resistance of the seal rings, the surface is frequently hard-faced by welding and then machining the contact surface of the seal ring. A fine surface finish of the seating area is necessary for good sealing when the valve is closed. Seal rings are not normally considered pressure boundary parts since the body has sufficient wall thickness to withstand design pressure without relying upon the thickness of the seal rings.
Valve spring – It is a coil spring, typically found in internal combustion engines, which holds a valve in a closed position. It ensures the valve returns to and seals tightly against its seat after being opened by the camshaft. The spring also maintains contact between the valve and camshaft to prevent ‘valve float’ which can cause damage.
Valve stem – The valve stem, which connects the actuator and the disk, is responsible for positioning the disk. It provides the necessary movement to the disk, plug, or the ball for opening or closing the valve, and is responsible for the proper positioning of the disk. It is connected to the valve handwheel, actuator, or the lever at one end and on the other side to the valve disc. In gate or globe valves, linear motion of the disk is needed to open or close the valve, while in plug, ball and butterfly valves, the disk is rotated to open or close the valve. Stems are normally forged, and connected to the disk by threaded or welded joints or other techniques. There are five types of valve stems. The first type is the rising stem with outside screw and yoke (OS&Y). The exterior of this stem is threaded, while the portion of the stem in the valve is smooth. The second type is the rising stem with inside screw. 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. The third type is the non-rising stem with inside screw. The threaded part of the stem is inside the valve and does not rise. The fourth type is the sliding stem. This valve stem does not rotate or turn. It slides in and out the valve to open or close the valve. The fifth type is the rotary stem. This is a normally used stem model in ball, plug, and butterfly valves. A quarter-turn motion of the stem open or close the valve.
Valve stem packing – Majority of the valves use some form of packing to prevent leakage from the space between the stem and the bonnet. Packing is normally a fibrous material (such as flax) or another compound (such as Teflon) which forms a seal between the internal parts of a valve and the outside where the stem extends through the body. Valve packing is to be properly compressed to prevent fluid loss and damage to the valve’s stem. If a valve’s packing is too loose, the valve leaks, which is a safety hazard. If the packing is too tight, it impairs the movement and possibly damage the stem.
Valve trim – The internal elements of a valve are collectively referred to as a valve’s trim. The trim typically includes a disk, seat, stem, and sleeves needed to guide the stem. The performance of a valve is determined by the disk and seat interface and the relation of the disk position to the seat. Because of the trim, basic motions and flow control are possible. In rotational motion trim designs, the disk slides closely past the seat to produce a change in flow opening. In linear motion trim designs, the disk lifts perpendicularly away from the seat so that an annular orifice appears.
Valve yoke – A yoke connects the valve body or bonnet with the actuating mechanism. The top of the yoke holds a yoke nut, stem nut, or yoke bushing and the valve stem passes through it. A yoke normally has openings to allow access to the stuffing box, and actuator links etc. Structurally, a yoke is to be strong enough to withstand forces, moments, and torque developed by the actuator.
Vanadium (V) – It is a chemical element having atomic number 23. It is a hard, silvery-grey, malleable e transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer (passivation) somewhat stabilizes the free metal against further oxidation. Vanadium is a ferrite promoter and carbide and nitride former. It acts as a scavenger for oxides, forms vanadium carbide (VC), and has a beneficial effect on the mechanical properties of heat-treated steels, especially in the presence of other elements. It slows up tempering in the range of 500 deg C to 600 deg C and can induce secondary hardening. Chromium-vanadium (0.15 %) steels are used for locomotive forgings, automobile axles, coil springs, torsion bars and creep resistance. Vanadium increases the yield strength and the tensile strength of C steel. The addition of small quantities of vanadium can considerably increase the strength of steels. Vanadium is one of the main contributors to the precipitation strengthening in micro-alloyed steels. When thermo-mechanical processing is properly controlled, the ferrite grain size is refined and there is a corresponding increase in toughness. The impact transition temperature also increases when vanadium is added.
Vanadium carbide (VC) – It is a hard, refractory ceramic material composed of vanadium and carbon. It is known for its high hardness, melting point, and electrical conductivity, making it valuable in several industrial applications. Specifically, it is an interstitial carbide, meaning the carbon atoms occupy spaces within the vanadium crystal lattice. Vanadium carbide is the inorganic compound. It is an extremely hard and refractory ceramic material. With a hardness of 9Mohs to 9.5 Mohs, it is possibly the hardest metal-carbide known. It is of interest because it is prevalent in vanadium metal and alloys.
Vanadium carbo-nitride (VCN) – It is a material composed of vanadium, carbon, and nitrogen atoms, frequently found as a thin film or coating. It shows a combination of properties from its constituent elements, making it suitable for several applications, including electro-chemical devices and as a wear-resistant coating on tools.
Vanadium nitride (VN) – It is a compound formed by the chemical bonding of vanadium and nitrogen. It is a hard, wear-resistant material with excellent electrical and thermal conductivity, making it useful in several applications, particularly in steel manufacturing and as a super-conductor.
van der Waals equation – It is a mathematical formula which describes the behaviour of real gases. It is an equation of state which relates the pressure, volume, number of molecules, and temperature in a fluid. The equation modifies the ideal gas law in two ways namely (i) it considers particles to have a finite diameter (whereas an ideal gas consists of point particles), and (ii) its particles interact with each other (unlike an ideal gas, whose particles move as though alone in the volume).
van der Waals force – It is one of the forces (attraction / repulsion) between molecules.
Vane-axial fans – These fans are suited for medium pressure to high pressure applications (up to 500 mm water column), such as induced draft service for a boiler exhaust. These fans can quickly accelerate to rated speed because of their low rotating mass. They generate flow in reverse directions, which is useful in many ventilation applications. These fans are suited for direct connection to motor shafts and are most energy efficient (up to 85 % if equipped with air foil fans and small clearances). These fans are relatively expensive compared to propeller fans.
Van ‘t Hoff equation – It relates the change in the equilibrium constant of a chemical reaction to the change in temperature given the standard enthalpy change for the process. The Van ‘t Hoff equation has been widely utilized to explore the changes in state functions in a thermodynamic system.
Van ‘t Hoff factor – It is a measure of the effect of a solute on colligative properties such as osmotic pressure, relative lowering in vapour pressure, boiling-point elevation and freezing-point depression. The van ‘t Hoff factor is the ratio between the actual concentration of particles produced when the substance is dissolved and the formal concentration which is to be expected from its chemical formula. For the majority of non-electrolytes dissolved in water, the van ‘t Hoff factor is essentially 1. For the majority of the ionic compounds dissolved in water, the van ‘t Hoff factor is equal to the number of discrete ions in a formula unit of the substance. This is true for ideal solutions only, since occasionally ion pairing occurs in solution. At a given instant a small percentage of the ions are paired and count as a single particle. Ion pairing occurs to some extent in all electrolyte solutions. This causes the measured van ‘t Hoff factor to be less than that predicted in an ideal solution. The deviation for the van ‘t Hoff factor tends to be highest where the ions have multiple charges.
Van ‘t Hoff plot – It is derived from this equation. It is especially effective in estimating the change in enthalpy and entropy of a chemical reaction.
Vapour – It is a substance in the gas phase at a temperature lower than its critical temperature, which means that the vapour can be condensed to a liquid by increasing the pressure on it without reducing the temperature of the vapor. A vapour is different from an aerosol. An aerosol is a suspension of tiny particles of liquid, solid, or both within a gas, e.g., water has a critical temperature of 647 K (374 deg C), which is the highest temperature at which liquid water can exist at any pressure. In the atmosphere at ordinary temperatures gaseous water (known as water vapour) condenses into a liquid if its partial pressure is increased sufficiently.
Vapour blanket cooling stage – It is also known as the vapour stage. It is the initial phase of quenching a heated metal object in a liquid medium, like oil or water. During this stage, the heated metal surface creates a thin, insulating layer of vapour around itself because of the high temperature difference between the metal and the liquid quenchant. This vapour layer considerably slows down the cooling rate, as heat transfer mainly occurs through radiation through this vapour barrier.
Vapour corrosion inhibitor – It is a type of coating which provides a method for both passive and active protection against corrosion.
Vapour degreasing – It consists of degreasing of work in the vapour over a boiling liquid solvent, the vapour being considerably heavier than air. At least one constituent of the soil is to be soluble in the solvent. Modifications of this cleaning process include vapour-spray-vapour, warm liquid-vapour, boiling liquid-warm liquid-vapour, and ultrasonic degreasing.
Vapour-deposited replica – It is a replica formed of a metal or a salt by the condensation of the vapours of the material onto the surface to be replicated.
Vapour deposition – It is a process where a material, initially in vapour form, is deposited onto a substrate to create a thin film or coating. This can be achieved through physical or chemical means, resulting in either physical vapour deposition (PVD) or chemical vapour deposition (CVD). Sputtering is also a process of vapour deposition.
Vapour deposition of thin films – It is the term covers a wide range of techniques for applying a thin film on the surface of the glass to change its technical or aesthetic properties e.g., scratch resistance, solar control. The methods employed to deposit the film include spraying onto hot glass, condensation in a vacuum and evaporation of the film material by heating.
Vapourization – It is also called boiling. It means the phase transition of a substance from a liquid to a gas. It is the process where a liquid or solid substance changes into a gas or vapour. This phase transition occurs when the substance gains enough energy, typically through heating, to overcome the intermolecular forces holding it in its original state.
Vapourization curve – It represents the boundary between the liquid and gaseous (or vapour) phases of a substance on a phase diagram. It shows the combinations of temperature and pressure at which the liquid and gas phases coexist in equilibrium. Along this curve, the liquid and its vapour are in dynamic equilibrium, meaning they evaporate and condense at the same rate.
Vapourization point – It is also evaporation point. It is not a specific, fixed temperature like boiling point. Vapourization is the process where a liquid changes into a gas or vapour at any temperature, not just the boiling point. While the rate of vapourization increases with temperature, vapourization can occur at any temperature, even below the boiling point.
Vapourization reduction deposition – It is also known as ‘physical vapour deposition. (PVD). It is a process where a material is vapourized and then condensed onto a substrate to form a thin film. It involves physically ejecting material from a source, frequently by heating or sputtering, and depositing it onto the desired surface. This process is used to create thin films with several applications, including semi-conductors, coatings, and optical fibres.
Vapour-liquid-solid (VLS) method – It is a mechanism for the growth of one-dimensional structures, such as nanowires, from chemical vapour deposition. The growth of a crystal through direct adsorption of a gas phase on to a solid surface is generally very slow. The vapour-liquid-solid mechanism circumvents this by introducing a catalytic liquid alloy phase which can rapidly adsorb a vapour to super-saturation levels, and from which crystal growth can subsequently occur from nucleated seeds at the liquid-solid interface. The physical characteristics of nanowires grown in this manner depend, in a controllable way, upon the size and physical properties of the liquid alloy.
Vapour-liquid-solid (VLS) process – It is a process using vapour feed gases and a liquid catalyst, and producing solid crystalline whisker growth. It is used to produce silicon carbide whiskers.
Vapour-phase epitaxy (VPE) – It is a thin-film deposition technique where a crystalline layer (epitaxial layer) is grown on a substrate by depositing material from a gaseous phase. Essentially, it is a type of chemical vapour deposition (CVD) where gaseous precursors react at the surface of a heated substrate to form a solid, crystalline film. This technique is crucial for creating semiconductor materials with specific crystalline structures and compositions. Epitaxy refers to the process of growing a thin film of a crystalline material on a substrate with a specific crystallographic orientation, meaning the deposited layer’s crystal structure is the same as that of the substrate.
Vapour-phase lubrication – It is a type of lubrication in which one or more gaseous reactants are supplied to the vicinity of the surface to be lubricated and which subsequently react to form a lubricious deposit on that surface.
Vapour plating – It is the deposition of a metal or compound on a heated surface by reduction or decomposition of a volatile compound at a temperature below the melting points of the deposit and the base material. The reduction is normally accomplished by a gaseous reducing agent such as hydrogen. The decomposition process can involve thermal dissociation or reaction with the base material. It is occasionally used to designate deposition on cold surfaces by vacuum evaporation.
Vapour pressure – It is also called equilibrium vapour pressure. The pressure exerted by a vapour which is in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. It is normally described as the tendency of particles to spontaneously escape from the liquid or solid state into the gaseous state and is used as an indication of a liquid’s evaporation rate.
Vapour pressure spring thermometer – It is a temperature-measuring device which utilizes the relationship between a liquid’s vapour pressure and its temperature within a closed system. It consists of a bulb containing a volatile liquid connected to a pressure-measuring element (like a spring) by a capillary tube. As the temperature of the bulb changes, the vapour pressure of the liquid inside varies, and this change is registered by the pressure-measuring element, indicating the temperature.
Vapour steam cleaners – These are cleaning appliances or devices which use steam to dry, clean, and sanitize surfaces. The steam is produced in a boiler which heats water to high temperatures to produce low-pressure, low moisture water vapour.
Varestraint test – It determines the susceptibility of the welded joint to hot cracking. The test utilizes external loading to impose controlled plastic deformation in a steel plate while a weld bead is being deposited on the long axis of the steel plate. The sample is mounted as a cantilever beam, and a pneumatically driven yoke is positioned to force the test piece downward when the welding arc reaches a predetermined position. By the choice of the radius to which the steel plate is bent, the severity of deformation causing cracking can be determined. Strain from 0 % to 4 % can be chosen according to the susceptibility of the joint to hot cracking. When the bending moment is applied transverse to the weld axis, the test is termed trans-varestraint test. A spot Varestraint test can also be conducted by keeping the arc stationary with bending applied at the moment the arc is extinguished.
Variability – In data analysis, variability also causes complexity and an additional dimension of the data analysis. Variability refers to the variation in the data flow rates. Frequently, data velocity is not consistent and has periodic peaks and troughs. Complexity refers to the fact that the large data are generated through a myriad of sources. This imposes a critical challenge that is the need to connect, match, cleanse and transform data received from different sources.
Variability of data – It is the degree to which random variables deviate from a central value or mean. In statistical terms, this is measured by the sample standard deviation or sample variance.
Variable – It is a characteristic or attribute of an object of study which can be measured or counted, and which can take on different values. Variables are fundamental to statistical analysis, as they represent the data points being analyzed. Variables can be quantified numerically (e.g., height, volume, and weigh) or categorized (e.g., colour).
Variable air volume (VAV) – It is a type of heating, ventilation, and air-conditioning (HVAC) system which varies the volume of conditioned air delivered to rooms.
Variable amplitude – In the context of waves or periodic functions, it refers to a situation where the amplitude of the wave or function changes over time or position. This means the ‘size’ or ‘strength’ of the oscillation is not constant, but varies, unlike a wave with constant amplitude where the peak-to-peak distance remains the same.
Variable area flow meters – The flow rate of gases and liquids can be determined simply, yet relatively accurately with variable area flow meters. The measuring medium flows upward through a vertical conical tube whose diameter increases in the upward direction. The upward flowing fluid lifts a float located in the tube to a height so that the annulus has an area which results in an equilibrium of the forces acting on the float. Three forces act on the float, normally one is downward force which is the gravitational force and there are two forces acting in an upward direction which are the buoyancy force and the flow resistance force. The annulus available for the flow changes as a result of the conical form of the meter tube with the elevation of the float. Hence, the float height provides information regarding the flow rate. When a glass meter tube is used, the measured value can be read directly from a scale. A typical range of variable area flow meter devices includes a metal tube and a glass tube line which are used for the most different applications. The characteristics of metal tube flow meter are (i) high pressure and temperature conditions, (ii) opaque measuring media, (iii) steam applications, (iv) high flow rate, (v) current and contact outputs, (vi) HART (Highway Addressable Remote Transducer) communication, and digital display. The characteristics of a glass tube line flow meter are (i) low-cost solution, (ii) visual check of measuring medium, (iii) extremely low-pressure conditions, and (iv) clear, transparent measuring medium.
Variable capacitor – It is a capacitor whose value can be changed, by rotating a shaft, squeezing a plate or by an electrical signal, e.g., used to tune a radio.
Variable costs – It consists of those costs which can be directly associated with the production of a unit of output, and whose total increases roughly linearly with the total number of units produced. These are the expenses which fluctuate in direct proportion to the level of production. In simpler terms, the more an organization produces, the higher is its variable costs going to be, and vice versa. These costs are directly tied to the volume of goods or services produced. The important variable cost components for production cost are (i) raw material cost, (ii) fuel and energy cost, (iii) power cost, (iv) maintenance cost, (v) utility cost, (vi) manpower cost, and (vii) inspection cost.
Variable crown – It refers to a roll whose shape or diameter varies along its length. It describes a roll where the diameter is larger in the middle than at the ends, and this crown can be adjusted or changed to control the flatness and shape of the rolled material. Variable crown rolls are used to control the flatness and shape of the rolled material (like steel) by adjusting the roll’s diameter profile.
Variable data – It refers to numerical data which can be measured and which can take on a wide range of values within a given range. It is also known as continuous data, as the values can fall anywhere along a continuous scale. This is in contrast to attribute data, which can only take on specific, distinct values.
Variable-frequency drive (VFD) – It is a power converter which varies the speed of an alternating current motor by changing its frequency. It is normally, today, a solid-state device. Variable frequency drive uses power electronics to vary the frequency of input power to the motor, hence controlling the motor speed.
Variable polarity plasma arc (VPPA) welding – It is a specialized welding process which utilizes a plasma arc with alternating polarity (both positive and negative) to join materials, particularly aluminum alloys. This technique offers advantages like high energy density, deep penetration, and efficient oxide layer removal, making it suitable for demanding applications such as aerospace and automotive manufacturing.
Variable-speed (VSD) – It is a device which controls the speed of a motor by varying the magnitude of one of its controllable variables such as voltage, current, or frequency. Obviously, the technique used to vary the speed largely depends on the load type of the drive. Variable speed drives have a wide variety of potential applications in electric drives. This is because of the possibility to drive different types of loads which include constant power loads, constant torque loads, and variable torque loads. Variable speed drive classification can be made based on voltage and power ranges of the drive.
Variable spring – In this spring, resistance of the coil to load varies during compression.
Variable stiffness spring – In this spring, resistance of the coil to load can be dynamically varied for example by the control system, some types of these springs also vary their length thereby providing actuation capability as well.
Variac – It is a brand of adjustable transformer, which can essentially continuously vary the ratio between primary and secondary.
Variance – It is a measure which quantifies the spread or dispersion of data points in a dataset relative to its mean (average). It essentially tells how far, on average, the data points deviate from the centre of the distribution. A higher variance indicates greater variability, meaning the data is more spread out, while a lower variance suggests the data points are clustered closer to the mean. Variance is calculated by averaging the squared differences between each data point and the mean.
Variational analysis – It is is a branch of mathematics which extends classical calculus of variations, optimization, and control theory. It provides a framework for studying optimization and equilibrium problems, particularly those with constraints, and applies perturbation and approximation techniques to analyze a wide range of problems, even those not inherently variational in nature.
Variational noise – It means variation in the product parameters from one unit to another as a result of the manufacturing process, e.g., the design nominal for a resistor can be 200 ohms. However, one manufactured resistor can have a resistance of 202 ohms while another can have a resistance of 197 ohms. It is a matter of manufacturing imperfection and can hence be dealt with, in part, at the process with such techniques as statistical process control. However, mitigating the forces of variational noise are also to be considered to be a product and process design issue. In fact, it is likely that variational noise can be dealt with in a more significant and fundamental way if it is thought of as a process and product design problem. Certainly, the concept of design for manufacturability and the current emphasis on the simultaneous engineering of products and processes have bearing on this issue.
Variational principle – It is a powerful mathematical concept used. It states that for a given system, the true solution (e.g., a physical state or a function) minimizes or maximizes a certain quantity (called a functional or a function) related to the system. Essentially, it provides a way to find the best approximation to a solution by finding the function which optimizes a related quantity.
Varicap – It means variable capacitor. It is normally a diode whose reverse-biased junction capacitance. can be varied by applied voltage.
Variety – In data analysis, variety refers to the structural heterogeneity in a dataset. Technological advances now allow the usage of various types of structured, semi-structured, and unstructured data. In steel organization large variety of input data are used which in turn generates a large variety of data as output. The data comes from different sources and is being generated by process instruments as well as by the people.
Varistor – It means variable resistor. It is a protective device which has a high resistance at low voltage but momentarily switches to lower resistance on exposure to a high voltage.
varmeter – It is an instrument which is used to measure reactive power in an electrical circuit, expressed in volt-amperes reactive (VAR). It essentially indicates the ‘wattless’ or non-working power component of an electrical system, which is related to the magnetic or capacitive fields in the circuit.
Varnish – In lubrication, it is a deposit resulting from the oxidation and / or polymerization of fuels, lubricating oils, or organic constituents of bearing materials. Harder deposits are described as lacquers, softer deposits are described as gums. Varnish is also a transparent surface coating which is applied as a liquid and then changes to a hard solid. It can be either gloss, satin or matte which can be used for protection or to improve aesthetic appearance. All varnishes are solutions of resinous materials in a solvent.
Varying load – It refers to a force or weight which changes its magnitude, direction, or point of application over a given length, area, or time period. This contrasts with a uniform load, where the force is constant. Varying loads can be further classified as regularly or irregularly varying, and they can be distributed linearly (uniformly varying) or non-linearly. There are three types of varying loads. Uniformly varying load (UVL) is a load which changes linearly along the length of a structural member (like a beam or bridge). The intensity of the load increases or decreases at a constant rate, e.g., a triangular load on a beam is a uniformly varying load. Irregularly varying load is a load which changes in a non-linear, unpredictable manner, e.g., a crowd of people moving randomly on a bridge. Linearly varying load is a load which varies directly with distance. This is frequently a type of uniformly varying load, where the load is zero at one end and increases linearly to the other.
V-bend die – It is a die normally used in press-brake forming. It is normally machined with a triangular cross-sectional opening to provide two edges as fulcrums for accomplishing three-point bending.
V-belt – It is a type of power transmission belt with a trapezoidal cross-section, normally used in conveyor systems.
VCC – This term is used as the positive supply voltage for circuits using bipolar junction transistors (BJT). The ‘C’ in VCC stands for collector. It is normally believed that the repetition of ‘C’ twice in VCC is to distinguish it from the collector voltage (VC). VCC is also used as the positive supply voltage for operational amplifiers, where the internal circuitry mainly consists of bipolar junction transistors, and for transistor-transistor logic (TTL).
V-cone blender – It is also known as a V-mixer or twin-shell blender. It is a type of equipment used for mixing dry powders and granules. It consists of two cylindrical shells joined at an angle (typically 70-degree to 90-degree) to form a ‘V” shape. This design enables the blender to tumble and mix materials through a diffusion mechanism, where particles repeatedly split and recombine as the vessel rotates.
VDD – This term is used as the positive supply voltage for circuits using field-effect transistors (FET). The ‘D’ in VDD stands for drain. It is normally believed that the repetition of ‘D’ twice in VDD is to distinguish it from the drain voltage (VD). VDD is also used as the positive supply voltage for operational amplifiers, where the internal circuitry mainly consists of field-effect transistors, and for complementary metal-oxide-semiconductor (CMOS).
Vector – It is a term which that refers to quantities which cannot be expressed by a single number, or to elements of some vector spaces. Historically, vectors were introduced for quantities that have both a magnitude and a direction, such as displacements, forces and velocity. It is also a graphic which is comprised of paths and are defined by start and end points. As a vector image is not made up of a number of dots they can be scaled and not lose any quality.
Vector control – It is a strategy for control of variable-speed motor drives.
Vector group – It is the classification of the connections of a polyphase transformer.
VEE – This term is used as the negative supply voltage for circuits using bipolar unction transistors (BJT). The ‘E’ in VEE stands for emitter. It is normally believed that the repetition of ‘E’ twice in VEE is to distinguish it from the emitter voltage (VE). VEE is also used as the negative supply voltage for operational amplifiers, where the internal circuitry mainly consists of bipolar junction transistors, and for transistor-transistor logic (TTL).
Vee-return idlers – These are idlers made of two rolls. On short conveyors, it can be necessary to equip the complete return run with the self-cleaning idlers. On long return belt runs, it is necessary to use these idlers only to the point where the material on the belt surface no longer adheres to and builds up on normal return idler rolls. Beyond this point, standard return idlers can be used. With the increased use of heavy, high-tension fabric and steel cable belts, the need for better support and belt training has resulted in the development of vee-return idlers. A basic vee-return idler consists of two rolls, each tilted at a 5-degree, 10-degree, or 15-degree angle. These rolls are either of the garland (suspended) or rigid design. The vee-return idler has some training effect on the belt, while allowing greater idler spacing because of its increased load rating. The trough shape of the belt also tends to reduce or eliminate vibration along the conveyor. Vee-return-idlers can be supplied with steel rolls, rolls coated with some type of polymer, or spaced disc of rubber, urethane, or other material.
Vehicle – It is the combination of a paint binder and solvents or diluents, which are used to put the binder in a liquid, usable form. Vehicle is also a machine designed for self-propulsion, normally to transport people, cargo, or both.
Vehicle-to-grid – It is a concept to use electric vehicle batteries as a form of grid energy storage.
Vehicular automation – It consists of automatic systems to assist, or replace, the driver of a vehicle.
Veil – It is an ultrathin mat similar to a surface mat, frequently composed of organic fibres as well as glass fibres.
Vein – It is a fissure, fault or crack in a rock filled by minerals which have travelled upwards from some deep source.
Veining – It is a sub-boundary structure in a metal which can be delineated because of the presence of a higher-than-average concentration of precipitate or solute atoms
Vello process – It is a drawing process used for the production of glass tubing. Glass from the furnace forehearth flows down through an orifice (ring) within which is a rotating conical-ended shaft (or mandrel) over and around which the glass flows. The tube-shaped glass is pulled from the end of the shaft by a tractor machine and turned through 90-degree into a horizontal position ready for cutting.
Velocity – It is a measure of speed and direction of an object. When related to fluids, it is the rate of flow of fluid particles in a pipe. The speed of particles in a fluid flow varies across the flow, i.e., where the fluid is in contact with the constraining walls (the boundary layer) the velocity of the liquid particles is virtually zero while in the centre of the flow the liquid particles have the maximum velocity. Hence, the average rate of flow is used in flow calculations. The units of flow are normally meters per second, and so on. The pressures associated with fluid flow are defined as static, impact, or dynamic. Velocity is a vector quantity which describes both the speed and direction of an object’s motion. It essentially tells a person how fast an object is moving and in what direction. Velocity is frequently defined as the rate of change of an object’s displacement over time. In data analysis, velocity refers to the rate at which data are generated and the speed at which it is analyzed and acted upon. These days, there is an unprecedented rate of data creation which is driving a growing need for real time data analysis and evidence-based planning. Traditional data management systems are not capable of handling huge data feeds instantaneously. This is where large data analysis technologies come into play. They enable the organization to create real-time intelligence from high volumes of ‘perishable’ data.
Velocity chart – It is a visual tool used in agile project management, particularly in Scrum, to track a team’s progress and predict future performance. It displays the quantity of work completed (frequently measured in story points) over a series of sprints, allowing teams to see how their velocity changes over time and to estimate how much work they can handle in upcoming sprints.
Velocity diagram – It is a graphical representation, typically using vectors, which illustrates the velocities of different points within a mechanism or system. It helps in visualizing and analyzing the motion, especially the relative velocities between points, in a mechanical system.
Velocity field – It is a function which describes the velocity of a fluid (or any moving medium) at every point in a given region and at a specific time. Essentially, it is a map which shows the speed and direction of motion for every location within that region. It is a vector field, meaning it assigns a velocity vector (which has both magnitude and direction) to each point.
Velocity pressure – It is the measure of the kinetic energy of a fluid.
Vena contracta – It is the point in a fluid stream where the cross-sectional area is at its minimum, and the fluid velocity is at its maximum, just downstream of an obstruction like an orifice or nozzle. It occurs because the fluid’s inertia causes it to contract after passing through the restriction before eventually expanding again. Vena contracta is the portion of a flow stream where fluid velocity is at its maximum and fluid static pressure and the cross-sectional area are at their minimum. In a control valve, the vena contracta normally occurs just downstream of the actual physical restriction.
Vendor inventory system – It is the inventory management system managed by the vendor organization. This stock management system helps the organization in keeping its inventory and to take an informed decision on the minimum and maximum stock levels.
Vendor Item drawing – It is a type of control drawing. It provides an engineering description and acceptance criteria for purchased items. It provides sufficient engineering definition for acceptance of interchangeable items within specified limits. It is used to provide engineering requirements for a purchased item. It is not the intent of a vendor item drawing to portray a complete design disclosure. This drawing discloses sufficient information to ensure identification and re-procurement of interchangeable items. The drawing includes (i) configuration, (ii) dimensions of item envelope and their limits, (iii) mounting and mating dimensions and their limits, (iv) interface characteristics and their limits, (v) acceptance criteria, (vi) performance, maintainability, reliability, environmental, and other functional characteristics, (vii) schematic, interconnection, or other appropriate diagram to define item function or provide inter-connection information.
Vendor management – It is a structured programme to manage suppliers and improve their impact on the buyer’s business. It includes managing vendor deliverables, working collaboratively to co-develop new processes, managing compliance as well as payment of invoices.
Vendor master data – It comprises all relevant information about goods and services sources. The vendor master data normally includes procurement history, contract records, inventory data, supply categories and other important information about vendors and suppliers.
Vendor registration – It is the process where a supplier formally provides an organization with their information to be recognized as a potential or current supplier. This process helps organizations gather necessary information about vendors, verify their credentials, and streamline the procurement process. It is a crucial step for organizations, especially those with a high volume of suppliers, to manage their vendor relationships effectively and ensure compliance with legal and regulatory requirements.
Vendor relationship management – It is the systematic coordination of interactions with external vendors and service providers within the computerized maintenance management system (CMMS). Vendor relationship management includes maintaining communication, tracking performance, and ensuring timely procurement of conveyor system components.
Vendor risk management (VRM) – The term suggests an enterprise-wide initiative which analyzes vendor behaviour and access, and thereby ensures that vendor does not create a situation where it can disrupt an enterprise’s operations in any way. The most common risk factors include organizational continuity risk, information security risk, operational risk, regulatory risk, financial risk as well as risk of losing reputation.
Vent – It is an opening in a vessel or other enclosed space for the removal of gas or vapour. It is also a small opening in a foundry mould for the escape of gases.
Vent cloth -It is a layer or layers of open-weave cloth used to provide a path for vacuum to ‘reach’ the area over a laminate being cured, such that volatiles and air can be removed. It also causes the pressure differential which results in application of pressure to the part being cured. It is also called breather cloth.
Ventilation – It is the process of ensuring proper airflow and cooling for conveyor components, preventing overheating and optimizing performance.
Venting – It is providing holes in fabrications to be galvanized to allow entrapped, heated liquids and gases to escape as pressure increases. All hollow sections are to be vented to allow molten zinc to freely enter and leave the fabrication, and allow condensation or moisture to escape. In the context of casting, venting refers to the process of creating openings in a mould to allow gases to escape during the pouring of molten metal. These openings, also called vents, are crucial for preventing gas-related defects in the final casting.
Vent mark – It is a small protrusion resulting from the entrance of metal into die vent holes.
Venturi – It is a short tube with a tapering constriction in the middle which causes an increase in the velocity of flow of a fluid and a corresponding decrease in fluid pressure and which is used especially in measuring fluid flow or for creating a suction.
Venturi effect – It is the reduction in fluid pressure that results when a moving fluid speeds up as it flows from one section of a pipe to a smaller section. The effect has several engineering applications, as the reduction in pressure inside the constriction can be used both for measuring the fluid flow and for moving other fluids (e.g., in a vacuum ejector).
Venturi flume flow meter – For flow measurement using measuring weirs the water is to be dammed which can cause changes in the inflow area under certain conditions. These restrictions do not apply to a Venturi flume. Hence, it can react to the smallest flow rates. As with the Venturi nozzle the constriction of the flow cross sectional area results in an energy conversion, which accelerates the measuring medium in the region of the constriction. The constrictions are normally at the sides. However, there are some however with elevated floor sections. The water level upstream of the flume inlet (headwater) is quiet and the water is in the subcritical regime. This occurs automatically because the water is dammed causing the flow velocity to decrease resulting in subcritical flow conditions. The acceleration of the water in the constricted region is to bring the water to a supercritical state, so that the tail water conditions do not have an effect on the flow level ahead of the constriction. Only when this condition is assured then a unique relationship exists between the level of the headwater and the flow rate. Subsequently, a subcritical flow state can be reached again after the channel expansion characterized by a hydraulic jump and a standing wave. A backflow must be avoided, because it influences the operation of the measuring system.
Venturi tubes – These consist of short pieces of narrow tube between wider sections of tube, used for exerting suction or measuring flow rate.
Venturi valve – It is a reduced-bore valve. A valve having a bore smaller in diameter than the inlet or outlet. For example, a 200 millimeters x 150 millimeters x 200 millimeters ball valve has 200 millimeters inlet and outlet connections, while the ball and seats are 150 millimeters. The flow through a venturi valve is reduced because of the smaller port. Venturi valves frequently can be economically substituted for plug valves.
Veracity – In data analysis, veracity represents the unreliability inherent in some sources of data. Since the big data is sourced from many different sources, as a result there is a need to test the quality / veracity of the data. The quality of the data only imparts the data its economic value. Hence, the need to deal with imprecise and uncertain data is another facet of data analysis.
Verification – It is the process of ensuring that a product, system, or component meets its specified requirements and design specifications. It focuses on confirming that the ‘thing’ is built correctly as per the documented standards and requirements.
Verification and validation (V&V) – These terms consist of independent procedures which are used together for checking that a product, service, or system meets requirements and specifications and that it fulfills its intended purpose. These are critical components of a quality management system such as ISO 9000. The words ‘verification’ and ‘validation’ are sometimes preceded with ‘independent’, indicating that the verification and validation is to be performed by a disinterested third party. In reality, as quality management terms, the definitions of verification and validation can be inconsistent. Sometimes they are even used interchangeably. For example, a standard adopted by the Institute of Electrical and Electronics Engineers (IEEE), defines them as given here. Validation is the assurance that a product, service, or system meets the needs of the customer and other identified stakeholders. It frequently involves acceptance and suitability with external customers. Verification is the evaluation of whether or not a product, service, or system complies with a regulation, requirement, specification, or imposed condition. It is frequently an internal process. Another standard defines validation and verification as procedures which ensures that the device fulfil their intended purpose. Validation means ensuring that the device meets the needs and requirements of its intended users and the intended use environment, while verification means ensuring that the device meets its specified design requirements.
Verified loading range – For testing machines, it is the range of indicated loads for which the testing machine gives results within the permissible variation specified.
Vermicular graphite iron – It is also called compacted graphite iron. It is the cast iron having a graphite shape intermediate between the flake form typical of gray cast iron and the spherical form of fully spherulitic ductile cast iron. An acceptable vermicular graphite iron structure is one which contains no flake graphite, less than 20 % spheroidal graphite, and 80 % compacted graphite. It is produced in a manner similar to that for ductile cast iron, but using a technique which prevents the formation of fully spherulitic graphite nodules.
Vermicular iron – It is a cast iron material with a unique graphite structure which provides properties between those of grey iron and ductile iron. It features a ‘worm-like’ or compacted graphite structure, offering a balance of strength, ductility, and thermal conductivity.
Vermiculite – It is a hydrous phyllosilicate mineral which undergoes considerable expansion when heated. Exfoliation occurs when the mineral is heated sufficiently. Commercial furnaces can routinely produce this effect. Vermiculite forms by the weathering or hydro-thermal alteration of biotite or phlogopite. It typically occurs as an alteration product at the contact between felsic and mafic or ultramafic rocks such as pyroxenites and dunites. It also occurs in carbonatites and metamorphosed magnesium-rich limestone. Associated mineral phases include: corundum, apatite, serpentine, and talc. It occurs interlayered with chlorite, biotite and phlogopite.
Vernier – It is a short auxiliary scale which slides along the main instrument scale to permit more accurate fractional reading of the least main division of the main scale.
Vernier caliper – It is a precision measuring instrument used to measure lengths, widths, diameters, and depths of objects with high accuracy. It utilizes a main scale and a Vernier scale to achieve finer measurements than a standard ruler. The Vernier scale allows for reading fractional parts of the smallest division on the main scale, enhancing precision.
Versailles Project on Advanced Materials and Standards (VAMAS) – It is an international collaboration aimed at supporting global trade in products which rely on advanced materials. It achieves this by fostering pre-normative research, leading to harmonized measurements, testing, specifications, and standards for these materials.
Versatile product – It is a product which can be used for several different purposes or in several different situations. It is adaptable and flexible, meaning it can be modified or adjusted to meet different needs and requirements. In essence, a versatile product is not limited to a single function or application.
Verson-Wheelon process – This process gas been developed from the Guerin process. It uses higher pressure and is mainly designed for forming shallow parts, using a rubber pad as either the die or punch. A flexible hydraulic fluid cell forces an auxiliary rubber pad to follow the contour of the form block and to exert a nearly uniform pressure at all points. The distribution of pressure on the sides of the form block permits the forming of wider flanges than with the Guerin process. In addition, shrink flanges, joggles, and beads and ribs in flanges and web surfaces can be formed in one operation to rather sharp detail in aluminum, low-carbon steel, stainless steel, heat-resistant alloys, and titanium.
Verson hydro-form process with rubber diaphragm – This process differs from other processes in that the die cavity is not completely filled with rubber but with hydraulic fluid retained by a 65 millimeters thick cup-shaped rubber diaphragm. This cavity is termed the pressure dome. A replaceable wear sheet is cemented to the lower surface of the diaphragm. More severe draws can be made by this method than in conventional draw dies since the oil pressure against the diaphragm causes the metal to be held tightly against the sides as well as against the top of the punch. Reductions in blank diameter of 60 % to 70 % are common for a first draw. When redrawing is necessary, reductions can reach 40 %. Low carbon steel, stainless steel, and aluminum in thicknesses from 0.25 millimeters to 1.65 millimeters are normally formed. Parts made of heat-resistant alloys and copper alloys are also formed by this process.
Versorium – It is an antique version of an electroscope.
Vertical bar graph – It is also known as a column graph. It is a pictorial representation of data. It is used to indicate and compare values in a discrete category or group, and the frequency or other measurement parameters (i.e., mean). In vertical bar graph, bars are shown in the form of rectangles spaced out with equal spaces between them and having equal width. The equal width and equal space criteria are important characteristics of a vertical bar graph. The height (or length) of each bar corresponds to the frequency of a particular observation. The height of a bar represents the quantity of information in a category. Vertical bar graphs are flexible, and can be used in a grouped or subdivided bar format in cases of two or more data sets in each category. By comparing the endpoints of bars, one can identify the largest and the smallest categories, and understand gradual differences between each category. It is advised to start the x-axis and y-axis from ‘0’. Illustration of comparison results in the x-axis and y-axis which do not start from ‘0’ can deceive people’s eyes and lead to over-representation of the results. One form of vertical bar graph is the stacked vertical bar graph. A stacked vertical bar graph is used to compare the sum of each category, and analyze parts of a category. While stacked vertical bar graphs are excellent from the aspect of visualization, they do not have a reference line, making comparison of parts of various categories challenging.
Vertical circular pressure vessel – It is a cylindrical container designed to hold fluids under pressure, where the cylinder’s long axis is oriented vertically. It is a common type of pressure vessel used in several industries for storing liquids or gases at a pressure different from the surrounding environment.
Vertical continuous casting machine – It is a type of continuous casting equipment where the entire casting and solidification process occurs in a vertical orientation. Molten metal is introduced into a vertically positioned mold, and as it solidifies, the continuous strand is drawn downwards. This method is particularly suitable for producing cylindrical shapes like rods, tubes, and pipes.
Vertical counter blow hammer – In these machines, two tups with nearly equal masses are driven by double-acting cylinders toward each other and impact in the centre of the machine. More energy is dissipated in the work piece than in the foundations and subsoil compared to single-acting hammers. Very high energy capacities are available in these machines which range from 30 kilo-newton meter to 2,000 kilo-newton meter.
Vertical curve – It is a curved section in a conveyor system which changes the conveyor’s elevation, needing specialized maintenance considerations.
Vertical firing – It is an arrangement of a burner such that air and fuel are discharged into the furnace in practically a vertical direction.
Vertical illumination – It is the light incident on an object from the objective side so that smooth planes perpendicular to the optical axis of the objective appear bright.
Vertical multi-stage pump – It is a type of centrifugal pump which uses multiple impellers mounted on a single vertical shaft within a single casing to increase fluid pressure in stages. Essentially, it is a compact pump design which achieves high-pressure pumping by passing the fluid through several impellers in series. The pump incorporates multiple impellers (stages), each increasing the fluid’s pressure.
Vertical position – It is the position of welding in which the weld axis is approximately vertical.
Vertical position (pipe welding) – It is the position of a pipe joint in which welding is performed in the horizontal position and the pipe may or may not be rotated.
Vertical rolls – These are a set of rolls positioned vertically in a mill stand. These rolls are used to control the width and shape of the material being rolled.
Vertical section – It is a representation of a solid object or area as if it has been cut along a vertical plane, showing the internal structure or features exposed by the cut. In essence, it is a drawing or view which reveals what people see if they have sliced through something from top to bottom.
Vertical section through a building – It shows details of the construction of the foundations, walls, floors, roof and other parts. The number of sections needed of a building depends on its size and complexity. Normally, there are at least two sections. One of these is a cross section, across the width of the building. The second is a longitudinal section, along the length of the building. Sections are intended to help the site engineer construct the building, so the exact position of the section is to be chosen to show as much construction as possible.
Vertical semi-continuous direct-chill (DC) casting process – It is a method used to produce long, solid shapes (like billets or ingots) from molten non-ferrous metals such as aluminum and copper. It involves pouring molten metal into a water-cooled mould and simultaneously withdrawing the solidified product downwards as more molten metal is added. This process is semi-continuous since it involves a batch-wise addition of molten metal to the mould while the solidified product is continuously withdrawn. The process name highlights the use of direct water cooling on the solidified shell as it emerges from the mould, facilitating controlled solidification.
Vertical stand – It is a rolling mill stand where the rolls are mounted vertically, meaning they are positioned on the side of each other. Vertical stand is up-drive type comprises a roll stand, mill spindles, a vertical gear reducer, a pinion stand, and a motor. To protect them from the roll cooling water and mill scale, the gear reducer and motor are installed on a concrete frame. There is also a lifting device under the roll stand that is installed to manage the position of the caliber to pass the level. The roll stand can be moved to the work side during stand changing. These stands are crucial for controlling the width of the rolled material.
Vertical strength – It refers to a material’s ability to withstand forces applied perpendicular to its surface, frequently involving compressive or tensile stresses. It’s a crucial property for designing structures that need to bear weight or resist deformation under load. Different types of vertical strength exist, including compressive strength (resistance to squeezing forces), tensile strength (resistance to pulling forces), and flexural strength (resistance to bending).
Vertical stress distribution – It refers to the way the force of gravity’s downward pressure is spread throughout a soil mass because of the weight of overlying soil and any applied loads. It is crucial for understanding how foundations behave and how much they might settle.
Vertical thinking – It is a thought process which moves forward in sequential steps after a positive decision has been made about the idea.
Vertical tubular boiler – Vertical tubular boiler is normally a smaller sized fire-tube boiler with vertical fire-tubes. Some hot water supply boilers are of the vertical tubular type.
Vertical turbine pump – It is a type of centrifugal pump designed to move water or other liquids from deep wells or reservoirs. It is characterized by its vertical orientation, with the pump’s impellers submerged in the liquid and the motor situated above the surface. These pumps are known for their ability to handle high flow rates and lift liquids to considerable heights, making them suitable for several applications. The pump’s vertical shaft allows it to be submerged in the liquid source, making it ideal for deep wells or reservoirs where a flooded suction (where the pump inlet is below the liquid level) is necessary.
Very high-speed integrated circuit (VHSIC) – It refers to a type of integrated circuit (IC) designed for high-performance computing characterized by its ability to switch signals and process data at very high speeds. Very high-speed integrated circuit program chips are designed to operate at significantly higher speeds than conventional ICs, enabling faster processing and data transfer.
Very high vacuum (VHV) – It is a vacuum where the pressure is extremely low, typically below 0.01333 millipascal. This is a higher vacuum level than a high vacuum (HV) and is frequently referred to as ultra-high vacuum (UHV). In very high vacuum, the mean free path of gas molecules is much larger than the dimensions of the vacuum chamber, meaning gas molecules rarely collide with each other.
Very large-scale integration (VLSI) – It is the ability to put hundreds of thousands of interconnected transistors onto one chip.
Very low-level waste (VLLW) – It is a sub-category of low-level waste (LLW with low radioactive properties such that it can be disposed of to an unspecified destination with other types of industrial wastes.
V-groove – It refers to a groove with a V-shaped cross-section. This shape is used in several applications, including construction, welding, and metal fabrication, for different purposes like creating a track for sliding, facilitating bending, or improving weld penetration.
V-groove weld – It is a type of groove weld.
V-guide – It is a feature on conveyor belts which provides tracking assistance by fitting into a V-shaped groove on the conveyor pulleys.
Viable – A Project is viable when it has been confirmed to be economically, socially, technically, and environmentally feasible and satisfies all the relevant United Nations Framework Classification (UNFC) Criteria of the ‘E’, ‘F’ and ‘G’ Axes which are needed for it to proceed.
Viable projects – Viable projects are current or future recovery by actual mining operations. Viable projects have been confirmed to be technically, social, environmentally, and economically acceptable to society with a likelihood under current conditions for success. The term ‘on production’ is used where the project is actually producing and selling or using one or more products as at the effective date of the evaluation. Although implementation of the project may not be 100 % complete at that date, the full project is to have all necessary approvals and contracts in place, and capital funds committed. If a part of the project development plan is still subject to separate approval and / or commitment of capital funds such that it is not presently certain to proceed, that part is to be classified as a separate project in the appropriate sub-class. The term ‘approved for development’ needs that all approvals / contracts are in place, and capital funds have been committed. Construction and installation of project facilities are to be underway or due to start imminently. Only a completely unforeseeable change in circumstances which is beyond the control of the developers is an acceptable reason for failure of the project to be developed within a reasonable time frame. The term ‘justified for development’ needs that the project has been demonstrated to be technically feasible and environmental-socio-economic viable, and there is a reasonable expectation that all necessary approvals / contracts for the project to proceed to development and operation is going to be forthcoming.
Vial – It is a small cylindrical glass vessel especially for holding liquid.
Vibrating – It is the process of removing excess zinc by rapidly shaking galvanized articles.
Vibrating feeder – It is also known as a vibratory feeder. It is an industrial machine which uses controlled vibrations to move materials, parts, or bulk goods from one point to another in a production process. It utilizes both vibration and gravity to propel the material along a designated path, frequently towards another machine or process. These feeders are designed to handle a variety of materials and can be found in several industries. Vibrating feeders are primarily used to transport materials or parts, ensuring a controlled and consistent flow towards the next stage of a process.
Vibrating screen – It is a mechanical device which separates materials based on size using vibration. It uses a vibrating motion to facilitate the separation of particles, allowing finer materials to pass through while retaining larger ones. This equipment is normally used to sort materials as per the specific size requirements. The core of the machine is a screen or mesh with openings of a specific size. A motor and exciter mechanism generate the vibrations that agitate the screen. Vibrating screens are characterized by motion components in the vertical plane ranging from +/- 3.5 to 6 g (acceleration due to gravity) or more. The lifting and dropping effects expand the material bed; individual particles are bounced along over the screen with reduced opportunity for finding and passing an opening. This is a disadvantage, compared with the smoother horizontal motion designs. But on the plus side, the strong normal force component acts to eject near-size particles stuck in the openings, thus resisting progressive blinding, and the turbulent expansion of the material bed prevents packing. These advantages gain strength with increasing bed depth and particle size. The two most common types of vibrating screen are the inclined and the horizontal. In the inclined screen, the single unbalance, rotating on a horizontal axis, generates a circular motion in the vertical plane. Since this motion has no positive transport property, the screen surface is sloped at 15-degree to 20-degree to cause the particle mass to travel at velocities of 20 meter per minute to 30 meter per minute. The horizontal screen employs a pair of unbalances, rotating in opposite directions on parallel horizontal axes, to generate a straight-line reciprocating motion, inclined to the plane of the screen surface at 40-degree to 50-degree. Travel rates on a horizontal surface range between 20 meter per minute and 25 meter per minute, and can be increased if necessary by inclining the screen downward at up to about 10-degree.
Vibration – It is a mechanical phenomenon whereby oscillations occur around an equilibrium point. Vibration can be deterministic if the oscillations can be characterized precisely (e.g., the periodic motion of a pendulum), or random if the oscillations can only be analyzed statistically (e.g., the movement of a tyre on a gravel road). Vibration can be desirable, e.g., the motion of a tuning fork, the reed in a wood-wind instrument or harmonica, a mobile phone, or the cone of a loudspeaker. In several cases, however, vibration is undesirable, wasting energy and creating unwanted sound, e.g., the vibrational motions of engines, electric motors, or any mechanical device in operation are typically unwanted. Such vibrations can be caused by imbalances in the rotating parts, uneven friction, or the meshing of gear teeth. Careful designs normally minimize unwanted vibrations.
Vibrational circular dichroism (VCD) – It is a spectroscopic technique which measures the difference in absorption of left-handed and right-handed circularly polarized light in the infrared (IR) region, specifically during vibrational transitions of chiral molecules. It is a type of circular dichroism (CD) which focuses on the vibrational energy levels of molecules, rather than electronic transitions like in electronic circular dichroism (ECD). Vibrational circular dichroism is a sensitive probe of molecular chirality, conformation, and interactions, particularly in complex systems like proteins and solids.
Vibration analysis – It is the practice of monitoring and analyzing vibrations in equipment components to detect potential issues and prevent equipment failure.
Vibration compaction – It is also known as vibro-compaction or vibro-flotation. It is a ground improvement technique used to densify loose granular soils by applying vibrations to rearrange the soil particles and reduce the void ratio. This process increases soil density, shear strength, and stiffness, and can reduce settlement and mitigate liquefaction risks. It is normally used in construction projects where weak or unstable soils are encountered, particularly for foundations and land reclamation.
Vibration density – It is also called tap density. It refers to the density of a powder after it has been compacted by vibration. This process minimizes the air gaps between powder particles, resulting in a higher density compared to the powder’s initial loose state (bulk density). Vibration density is a crucial parameter in powder metallurgy as it influences the properties and performance of the final sintered part.
Vibration isolation – Isolation means reduction in the transmissibility of the exciting forces from the equipment to the foundation and vice-versa. Vibration isolation devices have been used to achieve satisfactory performance. Isolation in broader sense includes (i) control of transmission of dynamic forces from equipment to the foundation and thereby to the adjoining structures and equipment, (ii) isolation of equipment from the vibration effects of the adjoining system, (iii) isolation from external forces like earthquake shock, and blast etc. In cases, where a bunch of vibratory equipments are to be mounted on a common elevated platform, vibration isolation can turn out to be a better proposition. Vibration isolation design for equipment foundation systems includes, isolation requirement, isolation design, selection of isolation devices, and influence of sub-structure (wherever applicable) on the response etc.
Vibration, sweep – A sweep vibration is defined as a traverse from one frequency to another. A sweep cycle swap from one frequency to another, and then back to the first frequency. It is used for testing protective cases.
Vibrator – It is an electro-mechanical interrupter, part of a direct current-to-alternating current converter in a battery-operated vacuum tube radio, or similar application. Some has additional contacts to act as a synchronous rectifier.
Vibratory ball mill – It is a type of grinding mill which uses high-frequency vibrations to impact and grind materials, creating fine powders. It is a versatile piece of equipment known for its efficiency in producing fine and ultrafine powders compared to traditional ball mills.
Vibratory cavitation – It is the cavitation caused by the pressure fluctuations within a liquid, induced by the vibration of a solid surface immersed in the liquid.
Vibratory compaction – It is a ground improvement technique which uses vibrations to densify loose or unstable soil, improving its stability and reducing settlement. This method involves using specialized equipment like vibratory rollers or probes to rearrange soil particles into a denser state, improving the soil’s mechanical properties.
Vibratory feeders – These feeders are used extensively in controlling the discharge of bulk materials from storing units and stockpiles and directing these materials onto the conveyor belts. They are especially suitable for a broad range of bulk materials, are being able to accommodate a range of particle sizes, and are being particularly suitable for abrasive materials. However, they are normally not suited to fine powders under 75 micrometers to 100 micrometers where flooding can be a problem. Also ‘sticky’ cohesive materials may lead to build-up on the pan leading to a reduction in flow rate. Bulk materials are conveyed along the pan of the feeder as a result of the vibrating motion imparted to the particles. The pan of the feeder is driven in an approximate sinusoidal fashion at some angle ‘theta’ to the trough. The conveying velocity and throughput depend on the feeder drive frequency, amplitude or stroke, drive angle and trough inclination, coefficient of friction between the bulk material and the pan as well as the parameters of the bulk material such as bulk density, particle density and general flow properties. The vibratory feeders are of following two types namely (i) electromagnetic vibrating feeders, and (ii) mechanical vibrating feeders.
Vibratory finishing – It is a process for deburring and surface finishing in which the product and an abrasive mixture are placed in a container and vibrated.
Vibratory mills – These mills do not rely on rotation for the main grinding action. The vibrating mill has a grinding chamber which is filled to around 65 % to 80 % of its capacity with grinding media such as balls or rods. The chamber is vibrated at a frequency of between 1,000 and 1,500 times per minute (can be variable speed) by cams or unbalanced weights. The grinding action is efficient and thorough. Grinding media material and chamber lining can vary depending on application. Vibrating mills are usually batch mills and can grind hard or soft materials. Maximum throughput is about 20 tons per hour. The feed size is normally kept fairly small. Although final product size can be as low as 0.005 millimeters, this type of mill is often used for less fine applications. Product size and shape is a function of the time spent in the mill, media type and size, and frequency of vibration.
Vibratory polishing – It is a mechanical polishing process in which a metallographic specimen is made to move around the polishing cloth by imparting a suitable vibratory motion to the polishing system.
Vibratory tube mill – It is a type of grinding mill which uses vibration to break down materials. It consists of a cylindrical tube filled with grinding media (like balls or rods) which vibrates, causing the media to impact and grind the material being processed. These mills are particularly useful for achieving fine particle sizes and can handle a wide range of materials.
Vibro-compaction -It consists of the use of vibration to compact an unshaped refractory during installation or test piece preparation.
Vicat softening point – It is the temperature at which a flat-ended needle of 1 square millimeter circular or square cross section penetrates a thermoplastic sample to a depth of 1 millimeter under a specified load, using a uniform rate of temperature rise.
Vickers hardness number (HV) – It is a number related to the applied load and the surface area of the permanent impression made by a square-based pyramidal diamond indenter having included face angles of 136-degree, computed from the equation HV = 2P sin [(a/2)/d square] = 1.854P/d square, where ‘P’ is applied load (kilogram-force), ‘d’ is mean diagonal of the impression (millimeters), and is the face angle of the indenter (136-degree). The Vickers number (HV) is also calculated using the formula HV = 1.854(F/D2), where with F is the applied load (measured in kg) and D2 the area of the indentation (measured in square millimeters). The applied load is normally specified when HV is mentioned.
Vickers hardness test – Vickers hardness is a measure of the hardness of a material, calculated from the size of an impression produced under load by a pyramid shaped diamond indenter. It is also called diamond pyramid hardness test. It permits the establishment of a continuous scale of comparable numbers which accurately reflect the wide range of hardnesses found in steels. It is a standard method for measuring the hardness of metals, mainly those with extremely hard surfaces. In this method of the hardness testing the surface is subjected to a standard pressure for a standard length of time by means of a pyramid shaped diamond. The diagonal of the resulting indention is measured under a microscope and the Vickers hardness value is read from a conversion table. The indenter employed in the Vickers test is a square-based pyramid whose opposite sides meet at the apex at an angle of 136-degree. The diamond is pressed into the surface of the material at loads ranging up to around 120 kilograms, and the size of the impression (normally less than 0.5 millimeter) is measured with the aid of a calibrated microscope. The Vickers test is reliable for measuring the hardness of metals, and also used on ceramic materials. To perform the Vickers test, the sample is placed on an anvil which has a screw threaded base. The anvil is turned raising it by the screw threads until it is close to the point of the indenter. With start lever activated, the load is slowly applied to the indenter. The load is released and the anvil with the specimen is lowered. The operation of applying and removing the load is controlled automatically. Several loadings give practically identical hardness numbers on uniform material, which is much better than the arbitrary changing of scale with the other hardness machines. A filar microscope is swung over the specimen to measure the square indentation to a tolerance of plus or minus 1/1000 of a millimeter. Measurements taken across the diagonals to determine the area are averaged. The correct Vickers designation is the number followed ‘HV’ (Hardness Vickers). The advantages of the Vickers hardness test are that extremely accurate readings can be taken, and just one type of indenter is used for all types of metals and surface treatments. Although thoroughly adaptable and very precise for testing the softest and hardest of materials, under varying loads, the Vickers machine is a floor standing unit that is rather more expensive than the Brinell or Rockwell hardness testing machines.
Vickers micro-indenter hardness number – It is also known as Vickers hardness (HV). It is a measure of a material’s resistance to indentation. It is calculated by dividing the load applied to a diamond indenter by the surface area of the resulting indentation. The indenter is a square-based pyramid with specific angles, and the hardness number is derived from the size of the indentation it creates.
Video camera tube – It is a family of vacuum tube devices which are used to pick up images and transmit them electronically.
Video cassette recorder (VCR) – It is an electronic device which records and plays video content stored on magnetic tape cassettes, mainly VHS or Beta formats.
Video processing – It consists of the techniques used to improve video images.
Video tape recorder (VTR) – It is an electro-mechanical device that records and plays back video and audio signals onto and from magnetic tape. Essentially, it is a tape recorder specifically designed for capturing and reproducing moving images and sound.
Vidicon – It is a camera tube in which a charge-density pattern is formed by photo-conduction and stored on a photo-conductor surface that is scanned by an electron beam.
View factor, F (A->B) – In radiative heat transfer, it is the proportion of the radiation which leaves surface A which strikes surface B. In a complex ‘scene’ there can be any number of different objects, which can be divided in turn into even more surfaces and surface segments. View factors are also sometimes known as configuration factors, form factors, angle factors or shape factors.
Vigilance – It refers to the state of being watchful and alert to potential issues, particularly those related to ethical conduct, compliance with rules and regulations, and the overall integrity of operations. It encompasses both preventative measures to avoid problems and mechanisms to address issues that arise.
Vigilant organization – Vigilant organization manages a process which routinely and effectively watches for, evaluates, and responds to those signals from the far reaches of its environment which are difficult to interpret. A vigilant organization is noteworthy for its ability to ‘see around the corners’, and attends to early signals of threats and potential opportunities. It has a superior peripheral vision capability which determines how well it senses and acts on these frequently confusing signals. This capability has the following five components.
Vinyl chloride – It is a colourless, flammable gas mainly used to produce polyvinyl chloride (PVC), a widely used plastic. It is also known as vinyl chloride monomer (VCM) or chloroethene. While crucial for manufacturing several products, vinyl chloride is a known human carcinogen.
Vinyl esters – These consist of a class of thermosetting resins containing esters of acrylic and / or methacrylic acids, many of which have been made from epoxy resin. Cure is accomplished, as with unsaturated polyesters, by copolymerization with other vinyl monomers, such as styrene.
Vinyl monomers – These are organic molecules containing a vinyl group (a carbon-carbon double bond with one substituent) which can participate in polymerization to form long-chain polymers. These monomers are crucial building blocks in the chemical industry, used to produce a wide variety of plastics, resins, and other materials.
Vinyl polymers – These are a group of polymers derived from substituted vinyl (H2C=CHR) monomers. Their backbone is an extended alkane chain [−CH2−CHR−]. In popular usage, ‘vinyl’ refers only to polyvinyl chloride (PVC).
Vinyl resins – These are polymers based on the polymerization of vinyl chloride and are widely used in surface coatings. They have good flexibility, chemical resistance, and freedom from taste, and are hence used frequently in beer and food cans. Vinyl resins are very susceptible to degradation under the influence of heat, ultra-violet, and oxidizing agents, and hence need stabilizers to get long-term performance.
Virgin filament – It is an individual filament which has not been in contact with any other fibre or any other hard material.
Virgin material – It is a material which has not been processed in any form other than its original manufacture.
Virgin metal – It is same as primary metal.
Virtual instrumentation – It is a software-intensive measuring system which can be programmed to emulate any of a number of conventional measuring instruments, or some combination of measuring functions.
Virtual leak – It is an apparent leak caused by the slow release of gas trapped within the system, rather than a real leak through a physical opening. These trapped gases, frequently from cavities, blind holes, or material imperfections, slowly bleed into the vacuum chamber, mimicking a leak. It is the semblance of a leak in a vacuum system caused by slow release of trapped gas. During a-rate-of rise test, the semblance of a leak in vacuum system is caused by a slow release of sorbed or occluded gas or gases on or in the surface and pores of all materials in a system which has been exposed to atmospheric pressure prior to evacuation.
Virtual manufacturer – It is an organization which focuses on the design and marketing of a product and outsources the manufacturing and assembly of the product to other organizations.
Virtual power plant – It is a strategy for managing a collection of disparate power sources, inter-connected with a communications network, as if they are a single centralized power plant.
Visco-elasticity – It is the property of materials which show both viscous and elastic characteristics when being deformed. Visco-elasticity is the result of the diffusion of atoms or molecules inside an amorphous material.
Viscometer – It is an instrument used to measure the viscosity of a fluid. For liquids with viscosities which vary with flow conditions. An instrument called a rheometer is used. Hence, a rheometer can be considered as a special type of viscometer. Viscometers only measure under one flow condition.
Visco-plasticity – It describes a material’s mechanical behaviour, showing both viscous and plastic properties, meaning it can deform both elastically and plastically under stress, and this deformation is time-dependent. Essentially, it combines characteristics of viscous fluids (like resistance to flow) and plastic materials (which undergo permanent deformation). This behaviour is frequently observed in materials undergoing high strain rates or at high temperatures.
Visco-plastic strain rate – It refers to the rate at which a material deforms (strain) when subjected to stress, considering both its viscous (time-dependent) and plastic (permanent) behavior. Unlike purely elastic or plastic materials, visco-plastic materials show time-dependent deformation under load and also retain some permanent deformation after the load is removed.
Visco-plastic stress analysis – It is a method used to determine the stresses and strains in materials which show exhibit both viscous and plastic behaviour, especially when subjected to time-dependent loading. It considers the material’s time-dependent deformation (viscosity) and permanent deformation (plasticity) under stress. This analysis is crucial for understanding the long-term behaviour and structural integrity of materials in applications where time-dependent effects are considerable.
Viscosity – – It is a measure of the internal friction of a fluid or its resistance to flow. It is a property of a gas or liquid which is a measure of its resistance to motion or flow. A viscous liquid has a much higher viscosity than water, and water has a higher viscosity than air. A viscous liquid, because of its high viscosity, flows very slowly and it is very hard to move an object through it. Viscosity (dynamic) can be measured in poise or centipoise, whereas kinematic viscosity (without force) is measured in stokes or centistokes. Dynamic or absolute viscosity is used in the Reynolds and flow equations. Typically, the viscosity of a liquid decreases as temperature increases. Viscosity is a measure of a fluid’s rate-dependent resistance to a change in shape or to movement of its neighbouring portions relative to one another. For liquids, it corresponds to the informal concept of thickness. Viscosity is defined scientifically as a force multiplied by a time divided by an area. Hence, its SI (International System of Units) units are newton-seconds per metre squared, or pascal-seconds. Viscosity quantifies the internal frictional force between adjacent layers of fluid which are in relative motion, e.g., when a viscous fluid is forced through a tube, it flows more quickly near the tube’s centre line than near its walls. Viscosity is a vital property of the lubricating oil since it influences the ability of the oil to form a lubricating film or to minimize friction.
Viscosity, absolute – The absolute viscosity of a liquid is defined as the ratio between the applied shear stress and the resulting shear rate.
Viscosity cup – It is an instrument used to determine a fluid’s thickness and flow resistance. This is done by introducing a sample of the fluid into a container with a hole in its bottom and recording the time it takes for the container to empty when draining the fluid through the opening. The faster the fluid is drained, the less viscous the fluid is and vice versa.
Viscosity index (VI) – It is the most frequently used method for comparing the variation of viscosity with temperature between different lubricating oils. It is a dimensionless number. The kinematic viscosity of the lubricating oil sample is measured at two different temperatures (40 deg C and 100 deg C) and the viscosity is compared with an empirical reference scale. Viscosity index is used as a convenient measure of the degree of aromatics removal during the base oil manufacturing process, but comparison of the viscosity index of different oil samples is only realistic if they are derived from the same distillate feedstock. Viscosity index is an expression of effect of change of temperature on the viscosity of oils. This change can be evaluated numerically and the result is expressed as viscosity index.
Viscosity index (VI) improver – It is an additive, normally a polymer, which reduces the variation of viscosity with temperature, hence increasing the viscosity index of an oil.
Viscosity, kinematic – It is the ratio of absolute viscosity to the specific gravity of the oil at the temperature at which the viscosity is measured. The unit of kinematic viscosity is ‘stokes’. For practical purposes, viscosity of petroleum oils is expressed in time in seconds taken by a given quantity of oil to flow through a standard capillary tube. It is expressed as Saybolt universal seconds at 40 deg C or at 100 deg C.
Viscosity, units of – For absolute viscosity, the CGS (centimeter-gram-second) unit is the poise (dyne second per square centimeter, the MKS (meter-kilogram-second) unit is the Poiseuille (newton second per square meter), which is equal to the SI (International System of Units) unit) 1 newton second per square meter or pascal second and which is equal to 10-poise. The English unit is the Reyn (pounds second per square inch), which is not normally used. For kinematic viscosity, the CGS unit is the Stoke (square centimeter per second), the SI unit is square meter per second (1 square meter per second is equal to 106 centistokes), and the English unit is the Newt (square inch per second), which is not normally used.
Viscous – It means possessing viscosity. This term is frequently used to imply high viscosity.
Viscous flow – It is a type of fluid motion where frictional forces (because of the fluid’s viscosity) play a considerable role and cannot be ignored. In viscous flow, the fluid is moving in layers, and the layer nearest the boundary (like a wall) is stationary because of the ‘no-slip condition’, causing friction at the boundary. This friction between layers is characterized by the fluid’s viscosity, which quantifies its resistance to flow. Viscous flow is characterized by the presence of frictional forces between different layers of the fluid. These forces arise from the interactions between fluid molecules and impede the fluid’s motion. In case of viscous flow, it is the flow of gas through a duct under conditions such that the mean free path is very small in comparison with the smallest dimensions of a transverse section of the duct. The flow can be either laminar or turbulent.
Viscous fluid – It is a fluid which resists flow because of the internal friction between its layers. This resistance is called viscosity, and it is what makes a fluid thick and sticky, like tar, rather than easily flowing like water.
Viscous friction – It is the frictional resistance because of the viscous or rheological flow of fluids.
Visibility – It is the measure of the distance at which an object or light can be clearly discerned. It depends on the transparency of the surrounding air and as such, it is unchanging no matter the ambient light level or time of day.
Visible – It is pertaining to radiant energy in the electro-magnetic spectral range visible to the normal human eye (around 380 nanometers to 780 nanometers).
Visible radiation – It is the electro-magnetic radiation in the spectral range visible to the human eye (around 380 nanometers to 780 nanometers).
Visible gold – It is the native gold which is discernible, in a hand sample, to the unaided eye.
Visible transmittance – It is the ratio of total transmitted lights to total incident lights. In other words, it is the quantity of light passing through a glazing surface divided by the quantity of light striking the glazing surface. A higher visible transmittance value indicates that a greater amount of incident light is passing through the glazing.
Vision – It sets out what the organization wants to accomplish, and it inspires employees and stake-holders. Vision statements describe (i) how things are different as a result of the activities of the organization, and (ii) how the organization wants to be seen by others. Good visions are aspirational. Some of them are hard‐to‐reach ideals while others are more modest or describe objectives which are achievable in the near future. In either case, the vision helps establish the unique contribution which the organization makes to society. Vision statement of the organization has a written format. It is to be inspiring and to provide a base to frame strategy for achieving the ultimate vision of the organization. The normal life span of a vision statement is 10 years to 20 years and it articulates the ultimate long-range goal of the organization. When developing a vision statement, the issues to be kept in view are (i) what the organization is to do for moving forward, (ii) when it is to be done, and (iii) how it is to be done. Some of the organizations while developing vision consider factors related to people, portfolio, partners, planet, profit and productivity. A powerful vision, when fully embraced and executed by the organization, can position the organization for industry-wide leadership. A well worded vision statement is to be graphic (painting a picture of the kind of organization which the management intends to create), directional (indicate kind of organization and strategic changes which can be forthcoming), focused (i.e., it is to be specific so that management is able allocate resources and make decisions), flexible (i.e., it is to be capable of change whenever needed), feasible (i.e., it is to be achievable), durable (i.e., it is to cater to the long-term interest of the stake-holders) and easy to communicate.
Visitor – It means anyone on the organization premises other than an employee of the organization or contractor. Injuries to a visitor are to be included as an organization employee since the organization has the duty of care and direct safety supervision. Hours visited can be added to the calculation for frequency purposes.
Visual examination – It is the qualitative observation of physical characteristics, observed by using the unaided eye or perhaps aided by the use of a simple hand-held lens (up to 10×).
Visual inspection – It is a non-destructive testing technique which provides a means of detecting and examining a variety of surface flaws, such as corrosion, contamination, surface finish, and surface discontinuities on joints (e.g., welds, seals, solder connections, and adhesive bonds). Visual inspection is also the most widely used method for detecting and examining surface cracks, which are particularly important because of their relationship to structural failure mechanisms. Even when other non-destructive techniques are used to detect surface cracks, visual inspection frequently provides a useful supplement. For example, when the eddy current examination of process tubing is performed, visual
inspection is often performed to verify and more closely examine the surface disturbance. Given the wide variety of surface flaws which can be detectable by visual examination, the use of visual inspection can encompass different techniques, depending on the product and the type of surface flaw being monitored. The methods of visual inspection involve a wide variety of equipment, ranging from examination with the naked eye to the use of interference microscopes for measuring the depth of scratches.
Visual or optical inspection – Visual and optical inspection techniques are used to examine the surface condition of a component. Visual testing is widely used for just about every conceivable surface condition. By its very nature, visual and optical testing can be simple and straight forward. At its simplest, a clean component can be inspected by an operator in adequate light with no equipment, it can be that easy. Frequently, the operator requires using optical equipment to aid the inspection, which can range from a hand-held magnifier lens to a flexible fibre-scope, or remote video systems. An experienced operator, under optimum conditions, can be able to detect even small tight cracks. Repeatability is, however, an issue. If conditions are not optimized, the same operator can miss the same crack on the same component on a repeat inspection. This is why, optical aids are frequently used to give the operator the best chance of finding the fault condition as frequently as possible. Inspection is needed to take place in a clean, comfortable environment with adequate lighting.
Visual presentation of data – It means presentation of the data in the form of diagrams and graphs. In these days, as it is known, every analysis of the data is supported with visual presentation since the visual presentation has several advantages namely (i) it relieves the dullness of the numerical data, (ii) it makes the comparison easy and this is one of the prime objectives of visual presentation of data, (iii) it saves time and effort, (iv) it facilitates the location of different measures and establishes the trends, (v) it has universal applicability since it is a universal practice to present the numerical data in the form of diagrams and graphs, and (vi) diagrammatic and graphic presentation have become an integral part of various studies. In fact, now a days, it is difficult to find a study without a visual support. It is because, the visual presentation is the most convincing and appealing way of presenting the data.
Vital area – It typically refers to a critical location or part of something which is essential to its function, survival, or success. vital areas are the areas which are to be protected in high consequence facilities. Identification of vital areas is an important step in the process of protecting against sabotage. Vital area identification is the process of identifying the areas in a facility around which protection is to be provided in order to prevent or reduce the likelihood of sabotage.
Vital components – These are essential parts that are necessary for the equipment to function correctly and safely. These parts are crucial for the overall performance, reliability, and longevity of the equipment. If a vital component fails, it can lead to a complete breakdown of the equipment or significantly impact its functionality.
Vitrification – It is the formation of a glassy phase in a ceramic body which serves to bind the particulate material together and close the pores.
Vitrification process – In a nuclear facility, it is used to solidify concentrated solutions of fission products separated during spent fuel reprocessing by mixing them with a glass matrix at high temperature. The fission products are normally metal oxides at the point of embedding in the glass.
V-mixer – It is also known as a V-blender. It is a type of mixing machine used to blend dry powders and granules in several industries. It features a V-shaped container which rotates on two supports, causing the materials inside to tumble and mix because of the gravity and shear forces. This gentle mixing action helps to create homogeneous blends without causing damage to the material. The distinctive V-shape allows for efficient mixing by promoting material movement and tumbling action.
V-notch – It is also known as a triangular notch. It is a type of weir or notch used to measure the flow rate of liquids in open channels or tanks. It is a sharp-edged opening in the shape of a ‘V’, typically made of metal, which is placed in the path of the flowing liquid. The flow rate is determined by measuring the head (height of the liquid above the bottom of the V-notch) and using established formulas which relate head to discharge. In impact testing, a V-notch refers to a specific type of notch machined into a test sample, normally used in the Charpy impact test. This notch, with its defined dimensions (e.g., 2 millimeters deep, 45-degree angle, and 0.25 millimeter radius) acts as a stress concentrator, ensuring that fracture initiates at a predictable location during the impact test. The V-notch design helps to standardize the test and allows for the accurate measurement of a material’s resistance to fracture under impact loading.
V-notch ball valve – It is a type of quarter-turn valve with a segmented ball featuring a V-shaped notch. This design allows for precise flow control and throttling of fluids containing solids, slurries, or fibrous materials by creating a shearing action between the ball and the seat as it rotates. The V-notch provides a linear flow characteristic, meaning the flow rate is directly proportional to the valve’s opening. The V-shaped notch allows for accurate modulation of flow rates, making it suitable for applications needing precise regulation.
V-notch weir – It consists of a thin plate weir with a V-notch cut into it. The weir is placed to obstruct open channel flow and allow water to flow over the notch. This enables a person to accurately measure the flow, by measuring the head upstream of the V-notch.
Voce model – It is a plasticity model used to describe the relationship between stress and plastic strain in materials, particularly during deformation. It is an empirical model, meaning it is based on observations rather than derived from fundamental physical laws. The model is characterized by its ability to represent the strain hardening and eventual saturation of stress in materials.
Void – It is a shrinkage cavity produced in castings or weldments during solidification. It is a term normally applied to paints to describe holidays, holes, and skips in a film.
Void content – It is the volume percentage of voids, normally less than 1 % in a properly cured composite. The experimental determination is indirect, i.e., calculated from the measured density of a cured laminate and the ‘theoretical’ density of the starting material.
Void fill – It consists of the types of materials used inside a box to package / stuff around the products to avoid damage. It can include foam, paper, air sacks and bubble wrap.
Voids – These consist of air or gas which has been trapped and cured into a laminate. Porosity is an aggregation of micro-voids. Voids are essentially incapable of transmitting structural stresses or non-radiative energy fields.
Volatile – It is a substance which evaporates readily.
Volatile content – It is the percent of volatiles which are driven off as a vapour from a plastic or an impregnated reinforcement.
Volatile inorganic compound – It is a compound composed of elements other than carbon (or with limited carbon content without carbon-carbon bonds) that readily evaporates or vapourizes at normal temperatures. These compounds have a high vapour pressure and low boiling point, allowing them to easily transition into a gaseous state.
Volatile matter – It consists of those products which are given off by a material as gas or vapour. It is determined by definite prescribed methods. It also refers to the components of a substance which readily evaporate or vapourize at a relatively low temperature, frequently under standard conditions. In the context of coal, volatile matter specifically refers to the gases and vapours, excluding moisture, released when a coal sample is heated to a high temperature (e.g., 950 deg C) in the absence of air.
Volatile organic compounds (VOC) – These are organic chemical compounds which evaporate easily at normal room temperatures and pressures. They are known for their high vapour pressure and low water solubility. Volatile organic compounds are normally found in products like paints, solvents, and cleaning supplies, and can be released into the air through processes like evaporation or ‘off-gassing’. There are a large number of volatile organic compounds. They include hydrocarbons (CxHy) and also other organic chemicals which are emitted from a very wide range of sources, including fossil fuel combustion, industrial activities, and natural emissions from vegetation and fires.
Volatiles – These are materials, such as water and alcohol, in a sizing or resin formulation, which are capable of being driven off as a vapour at room temperature or at slightly higher temperature.
Volatility – It is a material quality which describes how readily a substance vapourizes. At a given temperature and pressure, a substance with high volatility is more likely to exist as a gas, while a substance with low volatility is more likely to exist as a liquid or solid. Equivalently, less volatile substances condense more readily a gaseous state than highly volatile ones.
Volatilization – Volatilization of chemicals from powder is the transfer of the chemical as a gas through the powder-air interface under environmental conditions.
Volatilize – It is the process of a substance becoming a gas. In powder metallurgy, lubricants and binders can be removed from the compact by heating. Also, in sintering brass powder compacts, the zinc content can be diminished by evaporation because of the high vapour pressure of the metal.
Volcanic rocks – These are igneous rocks formed from magma which has flowed out or has been violently ejected from a volcano.
Volcanogenic – It is a term used to describe the volcanic origin of mineralization.
Volt (V) – It is a derived unit of electric potential, electric potential difference, and electro-motive force, defined as one joule of work per coulomb.
Voltage -It is also known as electrical potential difference, electric pressure, or electric tension. It is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to move a positive test charge from the first point to the second point. In the International System of Units (SI), the derived unit for voltage is the volt (V). The voltage between points can be caused by the build-up of electric charge (e.g., a capacitor), and from an electro-motive force (e.g., electro-magnetic induction in a generator). On a macroscopic scale, a potential difference can be caused by electro-chemical processes (e.g., cells and batteries), the pressure-induced piezo-electric effect, and the thermo-electric effect. Since it is the difference in electric potential, it is a physical scalar quantity.
Voltage alignment – It is a condition of alignment of an electron microscope so that the image expands or contracts symmetrically about the centre of the viewing screen when the accelerating voltage is changed.
Voltage compensation – It normally means adjustment of a voltage source to compensate for voltage drop. There are techniques which differ widely between a computer power supply and a long-distance power line.
Voltage contrast – In scanning electron microscopy, additional contrast in an image arising from increased emission of secondary electrons from negatively biased regions of a sample. This type of contrast is frequently used to advantage in the examination of micro-electronic devices.
Voltage contrast X-ray photoelectron spectroscopy (XPS) – It is a technique which combines traditional X-ray photoelectron spectroscopy with the application of a bias voltage to a sample. This allows for the analysis of both the chemical state and the local electrical potential of materials, particularly in the study of interfacial bonding, electrical defects, and electro-chemical processes. By measuring shifts in the binding energies of photoelectrons due to the applied voltage, people can gain insights into the electrical properties and behaviour of materials at a microscopic level.
Voltage-controlled amplifier – It is an amplifier which has its gain controlled by a voltage signal.
Voltage controller – It is a device which adjusts the (effective) voltage to a load.
Voltage converter – It is a device which changes electric power at one voltage to power at a second. It is a transformer is a common example of an alternating current (AC) voltage converter.
Voltage designation of cables – In the early days of electric power utilization, direct current (DC) has been used, but little now remains except for special applications and for a few inter-connections in transmission networks. Alternating current (AC) has several advantages and 3-phase alternating current is used almost exclusively throughout the world, so that suitable insulation and cable construction can be specified for the needed 3-phase alternating current service performance. The design voltages for cables are expressed in the form ‘Uo’ / ‘U’ (formerly ‘Eo’ / ‘E’). ‘Uo’ is the power frequency voltage between conductor and earth and ‘U’ is the power frequency voltage between phase conductors for which the cable is designed, ‘Uo’ and ‘U’ both being root mean square (r.m.s.) values. (r.m.s. is measured under the root of the sum of squares of all instantaneous voltages divided by the number of instantaneous voltages. The root mean square value of an alternating current is equivalent to the power consumption by direct current voltage).
Voltage division – It is a circuit which produces an output voltage that is some, perhaps adjustable, fraction of the input voltage.
Voltage doubler – It is a rectifier circuit which can produce an output direct current (DC) voltage of nearly twice the input alternating current (AC) voltage.
Voltage ratings of cables – The rating, or voltage class, of a cable is based on the phase-to-phase voltage of the system even though it is in a single or three phase circuit. For example, a 15 kilovolts rated cable (or a higher value) is to be specified on a system which operates at 7.2 kilovolts or 7.62 kilovolts to ground on a grounded wye 12.5 kilovolts or 13.2 kilovolts system. This is based on the fact that the phase-to-phase voltage on a wye system is 1.732 (the square root of 3) times the phase-to-ground voltage. Another example is that a cable for operation at 14.4 kilovolts to ground is to be rated at 25 kilovolts or higher since 14.4 times 1.732 is 24.94 kilovolts.
Voltage regulation – It is a measure of how a source maintains its output voltage for varying load.
Voltage regulator – It is a system which automatically stabilizes the voltage at which power is supplied to a downstream system.
Voltage source – In circuit theory, it is a hypothetical element which maintains a specified voltage between its terminals independent of the current through it.
Voltage spike – It is a transient electrical voltage which is higher than normal appearing on an electrical supply.
Voltage-to-current converter – It is a circuit which produces an output current proportional to an input voltage.
Voltammetry – It is the study of the current-voltage relationships observed when electroactive species in solution are subject to oxidation or reduction at electrodes under carefully controlled conditions. It involves probing a small region of a solution containing, e.g., metal ions, by performing small-scale electrolysis between an indicator microelectrode and a reference electrode. A reference electrode, such as the saturated calomel electrode (SCE), is by definition non-polarizable. That is, its potential remains the same regardless of the potential difference imposed between it and the indicator electrode. The latter is described as polarizable, because it faithfully adopts any potential imposed on it relative to the reference. If the potential difference between indicator and reference electrode can be controlled accurately and varied uniformly, criteria which modern potentiostatic devices ensure, the corresponding currents that flow reflect the nature and concentration of oxidizable or reducible solutes in solution. Currents flow because of the exchange of electrons between the indicator electrode and electroactive solutes. The latter are frequently metal ions, and the electrode processes monitored are reductions. The indicator electrode then acts as a cathode. Considerable care is necessary to ensure that electro-reducible material reaches the indicator electrode only by natural diffusion. The other important mass transfer processes, electrical migration and convection, are controlled rigorously; the former, an electric field effect, is related to the transport number of the metal ions and can be eliminated effectively by the presence of a large excess of a supporting, or base, electrolyte. The ionic components of this electrolyte (frequently potassium chloride) do not react with the indicator electrode at potentials at which the required species does, but the presence of the base electrolyte ensures that the transport number of the species whose analysis is required is reduced virtually to zero.
Volt-ampere – It is the unit of measurement for apparent power in an electrical circuit. It is the product of the root mean square voltage (in volts) and the root mean square current (in amperes). Volt-amperes are normally used for analyzing alternating current (AC) circuits. In direct current (DC) circuits, this product is equal to the real power, measured in watts (W). The volt (V)-ampere (A) is dimensionally equivalent to the watt. In SI (International System of Units) units, 1 V x A = 1 W. ‘VA’ rating is most used for generators and transformers, and other power handling equipment, where loads may be reactive (inductive or capacitive).
Volt-ampere reactive (VAR) – In electric power transmission and distribution, volt-ampere reactive (var) is a unit of measurement of reactive power. Reactive power exists in an AC circuit when the current and voltage are not in phase. Special instruments called varmeters are available to measure the reactive power in a circuit.
Volt-ampere (VA) curve – It is also known as a current-voltage curve. It is a graph which shows the relationship between the current flowing through an electrical component or circuit and the voltage applied to it. It visually represents how the current changes as the voltage varies, providing insights into the component’s behaviour and characteristics.
Volta potential – It is also called Volta effect, Volta potential difference, contact potential difference, and outer potential difference. In electrochemistry, it is the electrostatic potential difference between two metals (or one metal and one electrolyte) which are in contact and are in thermo-dynamic equilibrium. Specifically, it is the potential difference between a point close to the surface of the first metal and a point close to the surface of the second metal (or electrolyte).
Volterra integral equation – It is a type of integral equation where at least one of the limits of integration is a variable, typically the upper limit. This distinguishes it from Fredholm integral equations, where both limits are fixed. Volterra equations are broadly classified into first and second kind, depending on whether the unknown function appears only under the integral sign or also outside of it.
Voltmeter – It is an instrument which measures electrical cell potential.
Volume – It is defined as the space occupied within the boundaries of an object in three-dimensional space. It is a quantity which expresses the quantity of three-dimensional space an object or substance occupies. It is the space that a substance (solid, liquid, gas, or plasma) or shape occupies or contains. It is essentially a measure of how much space a shape contains. It is considered as the ‘size’ of a 3-dimension object in terms of the space it takes up. The SI (International System of Units) unit for volume is the cubic metre. In data analysis, volume refers to the magnitude of the data. It is the data generated by instruments in various processes and is normally generated in very large quantities as compared with a non-traditional data. Definitions of data volumes are relative and vary by factors, such as time and the type of the data.
Volume below tuyeres – It is the inner volume of the blast furnace between the horizontal planes through the centre-line of the tap hole and the centre-line of the tuyere.
Volume diffusion – It is one of the main diffusion mechanisms during sintering. It is predominant for larger particles and higher temperatures, and its diffusion coefficient for the same conditions is smaller than that for grain boundary diffusion, and much smaller than that for surface diffusion.
Volume filling – It means filling the volume of a die cavity or receptacle with loose powder, and striking off any excess quantity.
Volume fraction – It refers to the proportion of a constituent’s volume to the total volume of a mixture before mixing. It’s a dimensionless quantity, typically expressed as a number between 0 and 1, representing the fraction of the total volume occupied by a specific component, e.g., a volume fraction of 0.4 means that 40 % of the total volume is occupied by that particular component. Volume fraction is calculated by dividing the volume of a constituent by the total volume of all constituents before they are mixed.
Volume fraction of fibre – In a composite material, it is the proportion of the total volume which is occupied by the fibres. It is a crucial parameter which considerably influences the composite’s mechanical properties. Essentially, it is the ratio of the volume of fibres to the total volume of the composite.
Volume fraction of the matrix – In a composite material, it is the ratio of the volume occupied by the matrix phase to the total volume of the composite material. It essentially represents the proportion of the composite’s volume which is made up by the matrix material.
Volume fraction of void content – It is also called void fraction. It is a dimensionless parameter which represents the proportion of void space (empty space) within a material or structure relative to its total volume. It is essentially a measure of how much ‘empty space’ there is in a given volume. It is frequently expressed as a fraction (between 0 and 1) or a percentage (between 0 % and 100 %).
Volume of air – It is the number of cubic metres of air per minute expressed the outlet conditions of a fan.
Volume of production – It refers to the total quantity of goods or services produced by the organization. It is frequently measured over a specific period like a week, month, or year. It is a key metric for evaluating output capacity and efficiency in manufacturing and other production-based industries.
Volume ratio – It is the volume percentage of solid in the total volume of the sintered body.
Volume resistance – The volume resistance between two electrodes in contact with or embedded in a sample is the ratio between the direct voltage applied to them and that portion of the current between them which is distributed through the volume of the sample. The electrical resistance between opposite faces of a 1-centimeter cube of insulating material. It is also called specific insulation resistance.
Volume resistivity – It is the ability of a material to resist the flow of a current. It is measured per unit.
Volume shrinkage – It refers to the reduction in the overall volume of a powder compact during sintering, which is the high-temperature process that bonds the powder particles together. This shrinkage is mainly because of the densification of the powder particles, where pores between particles are reduced or eliminated as they fuse together.
Volume stability – It refers to a material’s ability to maintain its volume (or size) without significant changes, despite external factors or internal processes. This means the material doesn’t shrink or expand excessively because of the factors like temperature changes, chemical reactions, or applied stresses.
Volume totalizer – It is an instrument which measures and accumulates the total volume of a flowing substance, such as a liquid or gas, over a period of time. It essentially tracks the cumulative flow, providing a running total of the quantity which has passed through a flow meter or other measuring device. Volume totalizers with moving measuring chambers driven by the measuring medium are also known as displacement meters. They are suitable for both liquids and gases. They are direct volume totalizers since they transport the measuring medium in chambers with defined, geometrically limited volumes. Among the direct volume totalizers are those with measuring vanes (also known as turbine totalizers) and volume totalizers with forced flow changes. In this method a pulse total is generated which represents a specific (not geometrically bounded) volume.
Volumetric analysis – It is also called titration. It is a laboratory method of quantitative chemical analysis which is used to determine the concentration of an identified analyte. The procedure involves preparing a particular reagent as a standard solution of known concentration and volume (called the titrant or titrator) and allowing it to react with a solution of the analyte (called the titrand) to determine the latter’s concentration.
Volumetric flask – It is a piece of laboratory apparatus, a type of laboratory flask, calibrated to contain a precise volume at a certain temperature. Volumetric flasks are used for precise dilutions and preparation of standard solutions. These flasks are normally pear-shaped, with a flat bottom, and made of glass or plastic. The flask’s mouth is either furnished with a plastic snap / screw cap or fitted with a joint to accommodate a Poly-tetra-fluoro-ethylene (PTFE) or glass stopper. The neck of volumetric flasks is elongated and narrow with an etched ring graduation marking. The marking indicates the volume of liquid contained when filled up to that point. Volumetric flasks are of several sizes, containing from a fraction of a milli-litre to hundreds of litres of liquid.
Volumetric flow rate – It is also known as volume flow rate or volume velocity. It is the volume of fluid which passes per unit time. It is normally represented by the symbol ‘QV˙. Its SI (International System of Units) unit is cubic metres per second. It contrasts with mass flow rate, which is the other main type of fluid flow rate. In majority of the contexts, a mention of ‘rate of fluid flow’ is likely to refer to the volumetric rate. In hydrometry, the volumetric flow rate is known as discharge. The volumetric flow rate across a unit area is called volumetric flux, as defined by Darcy’s law and represented by the symbol ‘q’. Conversely, the integration of a volumetric flux over a given area gives the volumetric flow rate.
Volumetric flux – It is the rate of volume flow of a fluid through a unit area. It is essentially how much fluid passes through a specific area in a given quantity of time. In simpler terms, it is the flow rate of a fluid per unit area.
Volumetric modulus of elasticity – It is also known as bulk modulus of elasticity. It is a material property which describes its resistance to uniform compression. It is defined as the ratio of pressure (volumetric stress) to the resulting volumetric strain within the elastic limit. Essentially, it indicates how much a material deforms in volume when subjected to pressure from all sides.
Voluntary activity – It is any action or task which people choose to do of their own free will, without being coerced or forced. It is an activity done willingly, frequently without payment or other incentives. Volunteering, which is a type of voluntary activity, involves dedicating time and effort to benefit others or a cause.
Voluntary carbon offset mechanisms – These mechanisms are based on the notion that greenhouse gases produce the same effect on the climate wherever they are emitted from and that if in certain conditions it proves impossible to reduce emissions linked to one’s own activities, in theory enabling emissions to be cut elsewhere for having the same end result, e.g., organizations buy a ‘carbon di-oxide credit’ by financing a project in a developing country (or an emerging economy) which allows the same quantity of carbon di-oxide to be saved; or else they go onto the market and buy carbon credits generated by actions which enabled emissions to be avoided or credits resulting from quota surpluses. Industries can, however, help to reduce global greenhouse emissions by means of a voluntary carbon offset mechanism.
Voluntary carbon standard (VCS) – It is a quality standard for voluntary carbon offset industry. Based on the Kyoto Protocol’s Clean Development Mechanism, voluntary carbon standard establishes criteria for validating, measuring, and monitoring carbon offset projects.
Voluntary commitments – These consists of a draft article considered during the negotiation of the Kyoto Protocol which has permitted developing countries to voluntarily adhere to legally binding emissions targets.
Voluntary emission reductions (VER) – Voluntary emission reductions or verified emission reductions (VERs) are a type of carbon offset exchanged in the voluntary or ‘Over-the-Counter’ (OTC) market for carbon credits. Verified emission reductions are normally certified through a voluntary certification process. Verified emission reductions are normally created by projects which have been verified outside of the Kyoto Protocol. One VER (verified emission reduction) is equivalent to 1,000 kilograms (one ton) of carbon di-oxide emissions. Through these schemes, industries and individuals voluntarily compensate for their emissions or provide an additional contribution to mitigating ‘climate change’.
Volunteerism – It is the practice of doing work for good causes, without being paid for it.
Volute spring – It is a type of compression spring characterized by its spiral or coiled shape, resembling a snail shell or scroll. It is typically made from a flat strip of material wound into a conical form, where the coils overlap and are guided radially during compression. This unique structure provides high load capacity and long cycle life, frequently used in applications demanding high force and limited space, such as heavy machinery and automotive suspension systems. Volute springs are not cylindrical like traditional helical springs. They are conical, with overlapping coils that provide stability against buckling.
von Mises stress – It is also known as equivalent stress. It is a scalar value which represents the combined effect of multiple stress components on a material under complex loading. It is a theoretical measure used to predict the onset of yielding in ductile materials. Essentially, it provides a single value that can be compared to the material’s yield strength to determine if it will begin to deform plastically.
von Mises yield criterion -It states that yielding of a ductile material begins when the second invariant of deviatoric stress J2 reaches a critical value. It is a part of plasticity theory that mostly applies to ductile materials, such as some metals. Prior to yield, material response can be assumed to be of a linear elastic, non-linear elastic, or visco-elastic behaviour. The von Mises yield criterion is also formulated in terms of the von Mises stress or equivalent tensile stress. This is a scalar value of stress which can be computed from the Cauchy stress tensor. In this case, a material is said to start yielding when the von Mises stress reaches a value known as yield strengthσy. The von Mises stress is used to predict yielding of materials under complex loading from the results of uniaxial tensile tests. The von Mises stress satisfies the property where two stress states with equal distortion energy have an equal von Mises stress.
Vortex – In fluid dynamics, it is a region in a fluid in which the flow revolves around an axis line, which can be straight or curved. Vortices form in stirred fluids, and can be observed in smoke rings, whirlpools in the wake of a boat, and the winds surrounding a tropical cyclone, tornado or dust devil. Vortices are a major component of turbulent flow. The distribution of velocity, vorticity (the curl of the flow velocity), as well as the concept of circulation are used to characterize vortices. In majority of the vortices, the fluid flow velocity is highest next to its axis and decreases in inverse proportion to the distance from the axis.
Vortex determination methods – There are several methods of vortex determination. The vortices generate periodic pressure and velocity variations. These provide a corollary means for the measurement. The sensor is placed either behind the bluff body or in the bluff body in such a manner that it can vibrate freely (the location is determined by the nominal diameter and the type of connection). Its tongue is forced to vibrate at the shedding frequency by the pressure differences. Piezo-elements inside the sensor convert the resulting pressure forces into electrical measuring pulse signals which can be amplified. An arrangement of four Piezo-sensors is normally selected to cancel pipeline vibrations. If the flow profile of the measuring medium is distorted (vortices, swirl) as it flows into the measuring section, the vortices cannot form properly. For this reason, straight steadying sections are to be provided upstream of the device, the length of which depends on the type of the distortion. Vortex flow meters can be used for measuring the flow of steam, gases and liquids. The model of flow meter with integral mount design integrates the sensor and transmitter in a single unit with a local indicator for the flow rate and totalized flow value. The transmitter is based on a digital signal processor and generates the 4-20 mA (milli ampere) analog output signals. As a two-wire device, it needs a supply voltage of 14 volts DC (direct current) to 46 volts DC which is fed through the analog output two-wire line. A binary output is available in addition to the analog output. This output can be configured as a pulse output or limit contact (contact output). The measurement display for gases and liquids is made in direct reading engineering units. Utilizing an integrated Platinum-100 in the flow sensor, a saturated steam measurement or temperature monitoring option can be incorporated. The transmitter can also be mounted remotely at a distance from the sensor if a special cable is used.
Vortex flow meter – There are several examples of the effects of vortex formation at bodies around which there is flow. Normally a flow obstruction causes vortices. On a free-standing body vortices are formed on both sides which are alternately shed resulting in the formation of a Karman Vortex Street. If the geometric distance is ‘l’ between two consecutive vortices and the time interval is ‘t’ when viewed from a fixed reference point, then the vortex shedding frequency ‘f’ is around ‘l/t’, Strouhal discovered a relationship between geometry and velocity (v) in which ‘f’ is around ‘v/d’. In this relationship equation, ‘d’ is the diameter of the round bluff body. The Strouhal number ‘St’, a proportionality constant named after Strouhal, gives ‘f = St x (v/d)’. The requirement for the bluff body is that the geometry of vortex formation does not change with the flow rate and that the Strouhal number remains constant over a wide range of Reynolds number. The shape and the area ratio in the pipe define the manner of vortex shedding and the constancy of the Strouhal number. The pressure drop is not to be too large. The optimum shape of the bluff body has been determined empirically and through calculations. The minimum Reynolds number value ‘Rmin’ defines the lower range value, i.e. the span decreases with increasing viscosity. The upper limit of ‘R’ is so high that it is negligible for the upper range value.
Vortex formation – A projecting obstruction at the wall extends the length of the boundary layer and restrains the fluid even more in the vicinity of the wall so that downstream of this restriction a dead zone with a slightly negative pressure exists. The fluid flows from the region of higher velocity into this dead zone and creates vortices.
Vortex generator (VG) – It is an aerodynamic device, consisting of a small vane normally attached to a lifting surface or a rotor blade of a wind turbine. Vortex generators can also be attached to some part of an aerodynamic vehicle such as an aircraft fuselage or a car. When the airfoil or the body is in motion relative to the air, the Vortex generators create a vortex, which, by removing some part of the slow-moving boundary layer in contact with the airfoil surface, delays local flow separation and aerodynamic stalling, thereby improving the effectiveness of wings and control surfaces.
Vortex pressure relief valve – It is the valve which automatically adjusts air pressure without letting in water.
Voussoir – It is a wedge-shaped element, typically a stone, which is used in building an arch or vault. Although each unit in an arch or vault is a voussoir, two units are of distinct functional importance: the keystone and the springer. The keystone is the centre stone or masonry unit at the apex of an arch. The springer is the lowest voussoir on each side, located where the curve of the arch springs from the vertical support or abutment of the wall or pier.
V-port ball valve – It has either a ‘v’ shaped ball or a ‘v’ shaped seat. This allows the orifice to be opened and closed in a more controlled manner with a closer to linear flow characteristic. When the valve is in the closed position and opening is commenced, the small end of the ‘v’ is opened first allowing stable flow control during this stage. This type of design needs normally a more robust construction due to the higher velocities of the fluids, which quickly damages a standard valve.
V-process – It is a moulding (casting) process in which the sand is held in place in the mould by vacuum. The mould halves are covered with a thin sheet of plastic to retain the vacuum.
Vref – It refers to a ‘voltage reference’, which is a precision device designed to provide a stable and accurate reference voltage for other circuits. It is crucial for components like analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) where a precise voltage is needed for comparison or generation of analog signals.
V-ring seal – It is a seal consisting of a ring or nested rings that have a V-shaped cross section and which are normally made from elastomeric material. Spring loading is sometimes used to maintain contact between the seal and its mating surface. It is normally used to seal against axial motion.
V-shaped punch and die set -It is normally used for making 90-degree bend. The tools are made of hardened steel, and the surface of the tooling is frequently coated with a wear-resistant material to ensure longevity and durability.
V-spring – It is also known as a cantilever or meander V-spring. It is a type of spring made from a thin strip of metal, frequently stainless steel, bent into a V-shape. It is characterized by its ability to provide a consistent load over a wide range of deflections, making it suitable for both static and dynamic applications.
VSS – The term is used as the negative supply voltage for circuits using field-effect transistors (FET). The ‘S’ in VSS stands for source. It is normally believed that the repetition of ‘S’ twice in VSS is to distinguish it from the source voltage (VS). VSS is also used as the negative supply voltage for operational amplifiers, where the internal circuitry mainly consists of field-effect transistors, and for complementary metal-oxide-semiconductor (CMOS).
Vug – It is a small cavity in a rock, frequently lined with well-formed crystals. Amethyst normally forms in these cavities.
Vulcanization – It is the process of bonding or fusing rubber components, such as conveyor belts, using heat and pressure for repair or maintenance purposes. It is an irreversible process during which a rubber compound, through a change in its chemical structure, becomes elastic.
Vulcanizer – It is a mobile curing machine for field splicing (also called press).
Vulnerability – It refers to ‘the quality or state of being exposed to the possibility of being attacked or harmed, either physically or emotionally’. The understanding of social and environmental vulnerability, as a methodological approach, involves the analysis of the risks and assets of disadvantaged groups. Types of vulnerability include social, cognitive, or environmental etc. In relation to hazards and disasters, vulnerability is a concept that links the relationship that people have with their environment to social forces and institutions and the cultural values which sustain and contest them. The concept of vulnerability expresses the multi-dimensionality of disasters by focusing attention on the totality of relationships in a given social situation which constitute a condition that, in combination with environmental forces, produces a disaster. It is also the extent to which changes can harm a system, or to which the community can be affected by the impact of a hazard or exposed to the possibility of being attacked or harmed, either physically or emotionally.
Vulnerability analysis – It is also known as vulnerability assessment. It is a systematic process of identifying, classifying, and prioritizing security weaknesses in a system. This process helps organizations understand their security posture and take proactive steps to mitigate potential risks before they can be exploited by malicious actors. It involves identifying vulnerabilities in software, hardware, and network components, assessing their potential impact, and recommending appropriate remediation or mitigation strategies. This involves using various techniques, including automated scanning tools and manual inspections, to discover potential vulnerabilities. Examples of vulnerabilities include outdated software, misconfigurations, and security flaws.
V-X diagram – It is a graph of the isothermal or isobaric phase relationships in a binary system, the coordinates of the graph being specific volume and concentration.
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