GENERAL HAZARDS OF PLANT OPERATION

Uncontrolled chemical reactions are not the only sources of hazard in a process plant. This chapter briefly considers the risks of fire and explosion, and toxicological hazards. All types of hazard should be fully assessed by competent personnel using specialist advice where necessary. (See also case histories Al 70-78, pages 186-188.) 

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Process definition is considered further in this chapter and the general hazards of plant operation are considered in Chapter 7. Chapters 3,4 and 5 cover the evaluation of chemical reaction hazards and the effect of process maloperations. The selection of safety measures is the subject of Chapter 6. Chapter 8 covers the implementation and maintenance of safety measures. 

Description of hazard. Water plant operators and associated maintenance staff are frequently exposed to various respiratory hazards, including dusts, chemical vapors, and gases. When engineering controls, such as general and local exhaust ventilation systems, are not adequate to control the hazard, workers must be required to use respiratory protection. Emergency procedures may also require the use of emergency escape or self-contained respiratory protective equipment. 

For new sites with 50 tons or more of LPG the Control of Major Accident Hazards Regulations 1984 apply. For sites which will have 300 tons or more (shortly to be reduced to 200 tons or more) these Regulations impose additional duties on site operators which include the prior submission of a safety report . This report has to set out the potential hazards of the plant and the means by which the risks are reduced to an acceptable level. The LPGITA has produced a Guide to the Writing of LPG Safety Reports which supplements the general guidance in the HSE booklet HS(R)21. 

Benson and Ponton propose, based on this analysis, the concept of distributed manufacturing [139, 145], which will be referred to in detail in Volume 2 of this book series. Basically, they refer to small, transportable plants which are fed with reactants over the fence , hence using only non-hazardous, generally available materials by normal piping or standard transport. If an aggressive chemical is needed, it has to be made from environmentally friendly base materials as an intermediate on-site. Needless to say, effluents have to be completely harmless, plant operation has to be intrinsically safe, and the plant should be clean and quiet. 

General Safety Precautions. The preparation and handling of the items covered by this specification, and the subassemblies thereof, involve hazardous operations and therefore require explosives safety precautions. Use of this specification will not be construed as to relieve the contractor or manufacturer of responsibility for the safety of his operations. Listed below are certain minimum provisions which a contractor or manufacturer (who prepares the item covered) should observe in order to fulfill his responsibility for safety. At Bureau of Naval Weapons, Navy Department, and other government plants, these provisions are mandatory. Such other warnings and precautions, pertinent to the operational effectiveness or safety during preparation of the specified items, are included in detailed technical requirements of the specification... 

A hazard and operability study is a systematic procedure for critical examination of the operability of a process. When applied to a process design or an operating plant, it indicates potential hazards that may arise from deviations from the intended design conditions. The technique was developed by the Petrochemicals Division of Imperial Chemical Industries (see Lawley, 1974), and is now in general use in the chemical and process industries. 

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