Systematic Planning of General layout of a steel plant
Systematic Planning of General Layout of a Steel Plant
Designing of general layout of the steel plant consists of a mechanism which involves knowledge of the space requirements for the facilities and also involves their proper arrangement so that continuous and steady movement of the production cycle takes place. The general layout of the plant has a big contribution towards productivity, efficiency of the plant.
Designing the general lay out of the steel plant is a very important activity and needs highest of the attention. It is because once a steel plant construction is over; the basic nature of the plant general layout cannot be changed till the lifetime of the plant. Any modification in the layout at a later date not only is difficult but also involves a major capital expenditure. Further, the performance of the steel plant depends to a large scale on its general lay out. As normally the layout mistakes are of permanent nature besides being expensive, it is essential that a lot of time and efforts are spent during plant engineering for evolving the best layout of the plant. A typical general layout for a steel plant (Bethlehem Steel Plant) is shown in Fig 1.
Fig 1 Typical general layout for a steel plant
The term general layout is primarily being used to represent the physical arrangement of the various facilities of the plant. These facilities are needed for the production of the finish products from the raw materials and include (i) facilities for receiving of all the materials needed for production, (ii) production facilities as per technological requirements, (iii) support production facilities, (iv) facilities for movement and communication of men and materials, (v) facilities for product shipping, (vi) facilities for storages of various materials and products, (vii) facilities needed for administration, (viii) facilities needed for the welfare of human resource, (ix) facilities needed for the maintenance of environment, and (x) facilities needed for the safety and security.
The general layout of a steel plant is the physical arrangement of its production and supporting facilities such as production shops, equipment, machineries, buildings, and road, rail and pipe network etc. The layout determines the way in which materials and other inputs (such as information etc.) flow through the operation. The layout is to be planned to have smooth technological process flow of materials and utilities with least amount of handling from receipt of raw materials to the dispatch of the finish products. It involves judicious arrangement of all the facilities needed for smooth production. Defective planning of layout at engineering stage leads to inefficiency, inflexibility, large volumes of inventories and work in progress and high operating costs etc.
In short the overall objective of designer of the steel plant is to design a physical arrangement which involves allocation of necessary space and allocation of plant and facilities in such a manner so as to meet the requirements of the end product both quality and quantity wise while ensuring at the same time the economical production of the desired products.
For developing a proper general layout, the designer of the layout is required to have (i) the limitations associated with the land site, (ii) site map showing external roads, neighborhood and the land boundary, (iii) soil characteristics and contour map of the site showing levels, (iv) location of the availability of water, power and other utilities, (v) alignment of the external road and railway system and the direction of the incoming and the outgoing traffic, and the alignment for the external power transmission line and incoming water pipeline. Also the designer need to have (i) the basic knowledge of the selected technologies, processes as well as the plant and equipment, (ii) the plant capacities and planned future expansion, and (iii) statutory requirements.
The general layout of the steel plant is (i) to make best use of local natural conditions combined with rational use of land, (ii) having a systematic arrangement of plant units for creating synergies, (iii) to ensure that there are minimum possible efforts needed for various activities, and (iv) to make certain an effective protection of the environment.
There are several methods being used for the design of the plant general layout. These include (i) systematic layout planning (SLP), (ii) algorithms, and (iii) arena simulation. SLP method of designing the layout is best suited for a steel plant.
Definition of plant general layout
There are several definitions given for the plant general layout. A few of them are given below.
Moore has explained plant layout as ‘the plan of or the act of planning, an optimum arrangement of facilities, including personnel, operating equipment, storage space, materials handling equipment and all other supporting services along with the design of the best structure to accommodate these facilities’.
According to Riggs ‘the overall objective of plant layout is to design a physical arrangement that most economically meets the required output-quantity and quality’.
As per J L Zundi, ‘plant layout involves allocation of space and arrangement of equipment in such a manner that overall operating costs are minimized’.
According to Dr. MN Dastur, ‘ the general layout of an integrated steelworks is basically an exercise in making a rational arrangement of the main production units, the energy networks and the auxiliary shops, within the limitation of the selected site’.
Principles of designing a general layout
The general layout in the steel plant decides the location of different production facilities and the communication facilities between the production facilities. Production shop layout involves detailed location of equipment and machinery within a production facility.
There are eight principles which are used for designing a general layout. These are (i) principle of minimum travel, (ii) principle of sequence or flow, and (iii) principle of usage, (iv) principle of compactness, (v) principle of safety and satisfaction, (vi) principle of flexibility, (vii) principle of interdependence, and (viii) principle of minimum investment.
The principle of minimum travel ensures minimum movement of men and materials in the plant and it helps in saving the time as well as material wastage during the material movement. The principle of sequence or flow ensures production units are arranged as per the process flow needed by the production technology. This avoids unnecessary to and fro movement of the materials. The principle of usage ensures that the space requirement is based on its optimal utilization. The principle of compactness requires that all the significant factors are needed to be fully integrated and related so as to produce a well integrated general layout. The principle of safety and satisfaction needs that the layout is to have provisions for the safety for the plant and equipment as well as for the people working in the plant. It is to be planned, based on the comfort and convenience of the people working in the plant for making them feel satisfied. In this regards, the layout is to meet all the regulatory requirement. Here the safety also includes fire safety as well as the security. The principle of flexibility ensures that the layout allows improvements with minimum difficulties and at the minimum costs. In this regards the plant general layout is to keep provision of future expansion. The principle of interdependence requires that the interdependent units are to be located in close proximity of each other. The principle of minimum investment is to ensure that that the layout provides lower fixed capital investment without ignoring the installation of all the required facilities and by efficiently and optimally using the available facilities.
SLP method of layout design
SLP method for the layout planning is very popular and is being used not only for designing the plant general layout but also being used for the designing of the detailed layout of production shops as well as for designing layout of various facilities.
Before taking up the activity of designing the general layout, it is essential to study the wind rose diagram of the area. This diagram tells the designer about the directions and the frequencies of the wind blowing in the plant area throughout the year. Besides wind rose diagram other things which are important to study are (i) various levels of the land available within the land boundary, (ii) the approaches available for the road and rail for connecting the plant to external road and rail network, (iii) approach available for the incoming water pipeline, (iv) approach available for the transmission line for receiving the power from external power grid network, and (v) areas for the disposal of the plant solid and liquid wastes. Leveling of the land is not only a big task but also needs considerable expenditure. Utilizations of available land contour while finalization of the general layout is always desirable in order to reduce the leveling cost.
It is first necessary to consider the relationship between the various production processes needed as per the technology of the plant and the flow of materials (solids, liquids, and gases) needed for the production. For this, the normal practice is to make a material balance and flow diagram for the plant. For making the material balance and flow diagram, calculations are made for the materials (raw and auxiliary materials, fuels, and intermediate materials etc.) requirement based on the yields and recycling of the materials. For this various balance diagrams such as water balance diagram, energy balance diagram etc. are required to be developed. Finally, a comprehensive relationship is to be developed after providing due weightage to the various activities needed in the plant. A typical material balance and flow diagram is shown in Fig 2 and a typical water balance diagram is at Fig 3.
Fig 2 Typical material balance flow diagram
Fig 3 Typical water balance diagram
The next step is to divide the plant area into separate blocks and units as per the process flow before locating the facilities of the unit in the area. This step produces the plot plan of the plant. During the preparation of the plot lay out, importance is first given to the location of main production shops as per the production flow and then in subsequent step to the location of the support production facilities. The layout produced at this stage is known as the block layout of the plant.
After the block layout has been prepared to a level of satisfaction, then the locating of the facilities needed as per the production technology of the unit in the block starts based on the space requirement is to be carried out. While locating the facilities, the minimum distance needed between the facilities for meeting the statutory requirements as well as needed for the material movements (such as angle of the belt conveyor etc. is to be kept in mind.
After this, decision is needed for the location for the facilities for the storages and material flow. Decision on material flow is to include the receipt of materials from external sources and dispatch of the products from the plant. At this step, the piping network, power transmission network, and the road and rail network of the plant are also decided. While planning of the different networks, it is to be kept in mind that lengthier is the network, higher is the investment needed in addition to the higher amount of losses achieved during the transportation of materials. Also networks are to maintain the statutory requirements of minimum distances required for locating them.
Planning a good layout in a project
The decision on a layout is of utmost importance since it represents a long term commitment. If the relationship amongst output, area, and the technological process is not optimum, it affects the plant operation for its lifetime. The technical norms for the design of a good layout are given below.
Integration – A layout is required to have a close integration of men, materials and equipment and support services in order to get the optimum output of the resources.
Utilization of land (space) – A layout is to have proper utilization of both horizontal and vertical spaces. Both the height and the length of the facilities are to be optimized. The plant area is to be utilized in a most economic way.
Distance – A good layout is required to have minimum distances of travel for men and materials. The total distance of travel needed for the men and material is to be minimized as much as possible. Further, straight line movements are to be preferred in a good layout.
Production units’ layout – In a good layout, the production units are to be so arranged so that the movement of men, materials, intermediate products, and the finish products take place in the forward direction towards the final stage as per the technological flow.
Coordination – A good layout ensures the entry into and exit from any department is planned in such a manner that it is most convenient to both the departments which are dispatching or receiving. The layout is to be considered as a whole.
Flexibility – There is to be sufficient provision in a layout so as to modify the layout whenever the need arises for the plant expansion.
Accessibility – In a good layout, it is necessary that all the plant areas are readily accessible in order to facilitate the production and maintenance of the plant and equipment.
Safety – In a good layout, due consideration to industrial safety methods is necessary. The layout is to meet all the requirement of safety of not only men and plant but also meet the requirement for road safety, gas safety, electrical safety, and fire and explosion safety etc.
Material handling – A good layout is required to reduce the material handling to the minimum. Excessive level of material handling affects the time of operation and the production cost.
Other basic issues which are needed for consideration in the preparation of a good general layout include (i) It is to facilitate the production process and is to meet all the operational needs, (ii) it is to facilitate smooth receipt of raw materials, store materials and smooth dispatch of the end products, (iii) it is to facilitate the smooth flow and storage of intermediate products, (iv) It is to allow smooth flow of all the materials in the plant, (v) it is to allow flexibility in the operation, (vi) it is to help in a smooth technological flow for the production process, (vii) it is to provide convenience and comfort to the people working in the plant and to take care of their welfare and occupational health needs, (viii) it is to contribute towards employees’ efficiency, supervision, and control, (ix) it is to meet all the statutory requirements, (x) it is to have sufficient space to take care of future expansion, and (xi) it is to help in minimizing both capital and operational cost.
A general layout normally undergoes a series of revisions from the time it is first made and by the time the last foundation is poured. Even so the ‘final layout’ is necessarily a compromise between the desire to fulfill the various criteria given above and the limitations imposed by several other factors. But when the designer has the conceptual vision to look beyond the present need and immediate difficulties then the resultant layout has the logic and flexibility as well as the capability to give much needed operational performance of the plant in spite of the changed conditions.
The general layouts of Fukuyama and Kurashiki steel plants in Japan are shown in Fig 4 and Visakhapatnam steel plant at the capacity level of 3 million tons per annum per annum (Mtpa) is shown in Fig 5.
Fig 4 General layouts of Fukuyama and Kurashiki steel plants
Fig 5 General layout of Visakhapatnam steel plant