General – Consideration should be given to duplicating equipment that is operating satisfactorily in order to minimize spare parts.
General Safety Considerations for Plant Layout Levels
Process units operating in series flow with respect to each other should be grouped together or placed in rows to minimize interconnecting piping and operating costs. Units with heaters or furnaces should be grouped. Highly volatile units should be located to minimize hazard to surrounding facilities.
Utility areas should be adjacent to units that are the largest utility users. Intermediate tankage may be located near the associated units when space permits.
Storage tanks are generally located in areas remote from process units because of their large size and hazard.
The requirements contained herein shall be considered when using Table 1-A or 2-A or when establishing alternative spacing by using the Appendix. These guidelines should be reviewed when site surveys are conducted for the construction of new facilities.
Terrain
Whenever practical, locate process units, utility, flare, and other areas with similar open flames at a higher elevation than tank farms and other bulk quantities of hydrocarbons in order to minimize the potential for ignition of hydrocarbon vapor releases or liquid spills.
Where it is not feasible to locate tank farms at elevations lower than process areas, increased fire protection measures may be required to offset the increased potential for ignition. These measures may include all or some of the following: diversion diking, high-capacity drainage systems, vapor detection placed at release points and/or increased fire protection systems such as foam, water spray, or similar protection measures. Similar precautions for spills and vapor releases are needed when sitting plants containing extensive quantities of toxic materials.
Prevailing Wind
Prevailing wind should be considered when locating ignition sources such as furnaces and flares. Areas with high concentrations of personnel, such as office buildings, shop areas, and existing neighboring community areas, should also be considered in reference to prevailing wind to reduce exposure.
Careful consideration should be given to placement of facilities in relation to neighboring community facilities so that risks imposed by potential spills or releases of toxic materials, hydrocarbons or chemicals can be maintained. Spacing should be more stringently adhered to when adjacent to densely populated areas, such as shopping areas, schools, hospitals, public parks and residential areas.
Life Safety Code
Provisions for life safety shall be arranged in accordance with NFPA 101. Specific requirements are as follows:
a. Office areas located in separate buildings, or separated by fire-rated walls or partition from areas, shall have exits arranged in accordance with NFPA 101.
b. Warehouse areas for finished products shall have exits arranged in accordance with NFPA Storage Occupancies.
Cost Benefit Analysis
Given good loss prevention practice, large improvements in safety can often be achieved relative to poor practice at no additional cost. It is general experience that over the life time of a facility, good standard practice usually costs no more than bad and gives improvements in safety and reductions in
cost. Safety standards are written to a high minimum standard, and when they are met, additional improvements that provide incremental safety benefits may be expensive relative to the hazard.
Qualitative and quantitative assessment of hazards can be used to determine which levels of risk are unacceptable and must be removed by expenditure, and those that can be evaluated by combining life cycle cost analysis, hazards analysis and mitigation measures to achieve a level of safety that is as reasonable as practicable.
For example, In a plant layout case, it may be more cost effective to increase the blast resistance of an existing occupied building than to relocate the building, or a new unit at a prescribed distance. It is anticipated that a sound loss prevention approach optimizing the additional level of safety with the additional level of expenditure will be taken by the design engineer.