One of the first duties of the project Engineer will be to develop the plant layout (including the details equipment arrangement) which serves as a starting point for many of the specialized design functions such as Civil Engg. and piping designer, it will also influence every other design function, including process design. Because of its influence on all other work, the plant layout along with process design: is one of the most important factors in determining the sources of failure of the project.
FUNCTIONS OF PLANT LAYOUT:
One of the prime functions of the layout is determine the dimensions of the plot of ground that will be required for the plant or to determine whether the plant can be arranged to fit on our available site. If the development of the layout proceeds simultaneously with the development of the process design is likely to be obtained. Among other things, simultaneous development will help.
i) Determine the optimum proportions of various items of equipments.
ii) Determine whether gravity flows or pumps are desirable for liquid transport and
iii) Achieve maximum utilization of necessary building and structures while avoiding a design that would lead to wastage of structures. The lay-out asset the project engineer in co-ordinating the work of various designers far by allotting space for equipment and facilities so mechanical engineers can do their work simultaneous without interference. For instance by allocating blocks of space for piping runs, the lay out assures the piping designers that they can work in those space. Without visking interferences with structural members and assures the Civil Engineer that they can place their structural members in other spaces without interfering with piping. The development of layout also permits the orientation (Locating preciously) of those nozzles and vessels and heat exchanges so the designs of these items can be finalized before piping design has advanced very far.
FACTORS TO BE CONSIDERED IN PLANT LAYOUT:
During the development of layout and the process designer the project engineer should consider the needs for plant expansion. Shelter is required whenever there is need to protect operator equipment from whether, and very elaborate buildings may be required necessary to maintain a special atmosphere such as in the packing rooms of some pharmaceutical plants. In large size continuous process plants less and fewer shelters are being provided as the equipment becomes larger and more reliable and as the techniques for remote surveillance and control become better developed. It must be remembered that if shelter is provided, it may be necessary to province exceptionally ventilation in order to prevent the accumulation of hazardous vapors etc.
Maintenance requirements can be the most important factor in arrangement of equipment for some plants. Some equipments such as complex machinery and heat exchanges in severely corrosive a severely fouling services, may require frequent maintenance. At the very last such equipment requires easy access and it may attention should be paid to the major safely instruction in layout of isolation of hazards and escape for operation unless it is impossible for an operator be more a few steps away from an exit, one or more escape should be provided as to reduce to minimum the responsibility of fire or other hazards blocking his escape. In the case of novel process, it must be recognized that deifications are almost invariable, project Engineer should assure that sufficient space is kept clear to permit increasing a size of equipment or even for adding equipment to the plant.
Information required for plant layout:
1) A process flow sheet showing :
2) Every item of major equipment and its size.
3) Materials of construction of equipment and piping if these will introduce special support for other layout problems.
4) Those factors having a significant effect on piping design such as
i) Operating pressure and temperature.
ii) Flow quantity.
iii) The nature of flowing fuel example vapor liquid slurry paste. Etc.
5) Drawing for mechanical equipment showing.
a) Vertical dimensions.
b) Space required to be left clear for maintenance.
c) Location of connection.
6) Hazards of materials handled as they affect requirements for :
a) Separation of equipments.
c) The water or other barriers.
7) An area plan that shown neighbouring features that may influence the layout such as :
a) Steam, water sewage disposal and other sewage
b) Raw material and product storage at pipe lines.
c) Sources of atmosphere pollution that may affect the process (preliminary are consuming process) or the operation.
8) Load bearing ability of the soil and subsurface condition.
9) Atmosphere condition with regard to :
a) Extremes of weather which may make it desirable to provide shelter, a production for equipment or operation.
10) Prevailing wind direction if there are items such as in take or exhaust stack or furnaces, that should be located up or down wind of the remain of the plant.
11) Preferred operating and maintenance practices as they affect
a) Shelter that the operation are accumulated to
b) The need for the permanent or temporary shelter when performing maintenance our mechanical equipments such as pumps, Compressors, Centrifuges etc.
c) The selection between permanently installed holly became and mobile cranes for maintenance.
d) The location of locker rooms, Lunch rooms etc at each operating unit or at a central location.
12) Design Standards including the following :
a) Minimum permissible clearance between adjacent equipment or between equipment and adjacent structures.
b) Maximum permissible straight slopes and minimum rise between landings.
c) Preferred tube lengths for shell and tube heat exchanges.
d) Placement of over heads conduit either overheads or buried.
e) Location of Motor starter near the motor in the operating area or in a remote motor control centre.
The geographical location of the final plant can have strong influence on the success of an industrial venture. Considerable care must be exercised in selecting the plant site, and many different factors must be considered. Primarily, the plant should be located where the minimum cost of production and distribution can be obtained, but other factors, such as room for expansion and safe living conditions for plant operation as well as the surrounding community, are also important.
A general consensus as to the plant location should be obtained before a design project reaches the detailed estimate stage, and a firm location should be established upon completion of the detailed estimate design. The choice of the final site should first be based on a complete survey of the advantages and disadvantages of various geographical areas and, ultimately, on the advantages and disadvantages of available real estate. The following factors should be considered in selecting a plant site:
1. Raw materials availability
3. Energy availability
5. Transportation facilities
6. Water supply
7. Waste disposal
8. Labor supply
9. Taxation and legal restrictions
10. Site characteristics
11. Flood and fire protection
12. Community factors:
The factors that must be evaluated in a plant location study indicate the need for a vast amount of information, both quantitative (statistical) and qualitative. Fortunately, a large number of agencies, public and private, publish useful information of this type greatly reducing the actual original gathering of the data.
Raw materials availability:
The source of raw materials is one of the most important factors influencing the selection of a plant site. This is particularly true if large volumes of raw materials are consumed, because location near the raw materials source permits considerable reduction in transportation and storage charges. Attention should be given to the purchased price of the raw materials, distance from the source of supply, freight or transportation expenses, availability and reliability of supply, purity of the raw materials, and storage requirements.
The location of markets or intermediate distribution centers affects the cost of product distribution and the time required for shipping. Proximity to the major markets is an important consideration in the selection of a plant site, because the buyer usually finds it advantageous to purchase from nearby sources. It should be noted that products as well as for major final products need for markets.
Power and steam requirements are high in most industrial plants, and fuel is ordinarily required to supply these utilities. Consequently, power and fuel can be combined as one major factor in the choice of a plant site. Electrolytic processes require a cheap source of electricity, and plants using electrolytic processes are often located near large hydroelectric installations. If the plant requires large quantities of coal or oil, location near a source of fuel supply may be essential for economic operation. The local cost of power can help determine whether power should be purchased or self generated.
If the plant is located in a cold climate, costs may be increased by the necessity for construction of protective shelters around the process equipment, and special cooling towers or air conditioning equipment may be required if the prevailing temperatures are high. Excessive humidity or extremes of hot or cold weather can have a serious effect on the economic operation of a plant, and these factors should be examined when selecting a plant site.
Water, railroads, and highways are the common means of transportation used by major industrial concerns. The kind and amount of products and raw materials determine the most suitable type of transportation facilities. In any case, careful attention should be given to local freight rates and existing railroad lines. The proximity to railroad centers and the possibility of canal, river, lake or ocean transport must be considered. Motor trucking facilities are widely used and can serve as a useful supplement to rail and water facilities. If possible, the plant site should have access to all three types of transportation, and, certainly, at least two types should be available. There is usually need for convenient air and rail transportation facilities between the plant and the main company headquarters, and effective transportation facilities for the plant personnel are necessary.
The process industries use large quantities of water for cooling, washing, steam generation, and as a raw material. The plant, therefore, must be located where a dependable supply of water is available. A large river or lake is preferable, although deep wells or artesian wells may be satisfactory if the amount of water required is not too great. The level of the existing water table can be checked by consulting the state geological survey, and information on the constancy of the water table and the year round capacity of local rivers or lakes should be obtained. If the water supply shows seasonal fluctuations, it may be desirable to construct a reservoir or to drill several standby wells. The temperature, mineral content, site or sand content, bacteriological content, and cost for supply and purification treatment must also be considered when choosing a water supply.
In recent years, many legal restrictions have been placed on the methods for disposing of waste materials from the process industries. The site selected for a plant should have adequate capacity and facilities for correct waste disposal. Even though a given area has minimal restrictions on pollution, it should not be assumed that this condition would continue to exit. In choosing a plant site, the permissible tolerance levels for various methods of waste disposal should be considered carefully, and attention should be given to potential requirements for additional waste treatment facilities.
The type and supply of labor available in the vicinity of a proposed plant site must be examined. Consideration should be given to prevailing pay scales, restrictions on number of hours worked per week, competing industries that can cause dissatisfaction or high turnover rates among the workers, and variations in the skill and productivity of the workers.
Taxation and legal restrictions:
State and local tax rates on property income, unemployment insurance, and similar items vary from one location to another. Similarly, local regulations on zoning, building codes, nuisance aspects, and transportation facilities can have a major influence on the final choice of a plant site. In fact, zoning difficulties and obtaining the many required permits can often be much more important in terms of cost and time delays than many of the factors discussed in the preceding sections.
The characteristics of the land at a proposed plant site should be examined carefully. The topography of the tract of land and the soil structure must be considered, since either or both may have a pronounced effect on construction costs. The cost of the land is important, as well as local building costs and living conditions. Future changes may make it desirable or necessary to expand the plant facilities. Therefore, even though no immediate expansion is planned, a new plant should be constructed at a location where additional space is available.
Flood and fire protection:
Many industrial plants are located along rivers or near large bodies of water, and there are risks of flood or hurricane damage. Before selecting a plant site, the regional history of natural events of this type should be examined and the consequences of such occurrences considered. Protection from losses by fire is another important factor in selecting a plant location. In case of a major fire, assistance form outside fire departments should be available. Fire hazards in the immediate area surrounding the plant site must not be overlooked.
The character and facilities of a community can have quite an effect on the location of the plant if a certain minimum number of facilities for satisfactory living of plant personnel do not exit, it often becomes a burden for the plant to subsidize such facilities. Cultural facilities of the community are important to sound growth. Churches, libraries, schools, civic theaters, concert associations, and other similar groups, if active and dynamic, do much to make a community progressive. The problem of recreation deserves special consideration. The efficiency, character, and history of both state and local government should be evaluated. The existence of loss taxes is not in itself a favorable situation unless the community is already well developed and relatively free of debt.
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