Hazard Evaluation Procedures

The evaluation of hazards in a process starts at the initial screening of the process parameters. Several technical issues that will need more attention will arise from this screening procedure. Hazard evaluation procedures, however, are no substitutes for engineering codes of practice and for design standards, but are used as supplementary ideas and concepts. A prerequisite for any process hazard evaluation is a full knowledge of the chemistry of the process (including potential unwanted side reactions) with supporting data. 

Nine commonly used hazard evaluation procedures are highlighted in the short summary statements that follow. These procedures can be applied not only to the design of a new plant but also can be used to review safety conditions of existing plants, particularly regarding an update of current standards and operations. 

This procedure is based on the use of checklists which are applied to every stage of process design and operation to ensure compliance with standards, codes, good engineering practices, and well defined operating procedures. In this way, prior experiences can be implemented and used to prevent recurrence of incidents that may have happened in die past. Examples of checklists can be found in [2,3,251]. 

The Dow and Mond Indexes provide a relative ranking of the hazards and risks in a chemical process plant. This is accomplished by assigning penalties and credits based on plant features such as the presence of hazardous materials and the safety devices which can mitigate any hazardous effects. Penalties and credits are then combined into a single hazard index for the process unit in question. 

The indexes can be used to identify those units which require the highest priority for attention from a viewpoint of safety review. They are also useful in designing layout and spacing of equipment in process plants to avoid domino effects following an incident [2,3,252-254]. 

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Center for Chemical Process Safety, Guidelinesfor Hazard Evaluation Procedures, American Institute of Chemical Engineers, New York, 1992. 

Is a decommissioning phase hazard evaluation needed The AIChE/CCPS text. Guidelines for Hazard Evaluation Procedures, Second Edition, offers direction for addressing this type of evaluation. 

The following checklist contains a number of questions which can aid in identifying inherently safer process options. The list is adapted from CCPS (1993a). Other checklists, particularly the extensive checklist in Appendix B of the Guidelines for Hazard Evaluation Procedures, 2nd Edition with Worked Examjzles (CCPS, 1992) contain many questions which are related to inherent safety. 

These accidents would have been prevented by 1) adequate process safety design, 2) proper-procedures to prevent the initiation, 3) hazard evaluation procedures to identify and correct Iia/.ards hc fure accident occurrence, and 4) containment systems to prevent release into the aimosphci c,... 

CPI. The first book, Guidelines for Hazard Evaluation Procedures (HEP Guidelines), eovers methods for identifying and qualitatively assessing chemical process hazards. 

Adapted from "Guidelines for Hazard Evaluation Procedures, CCPS, AICliE, New York City, NY, 1992. 

G.A. Page. "Hazard Evaluation Procedures, American Society of Safety Engineers. Professional Dc clopmeiit Conference and Exposition, Las Vegas, NV. American Society of Safety Engineers, Dcs Plaines, IL, 1988. 

AIDUE, Guidelines of Hazard Evaluation Procedures , CCPS, AlCHE, New York Cibi, 1982. 

Guidelines for Hazard Evaluation Procedure , CCPS, AICHE, 1992. 

The CCPS publication Guidelines for Hazard Evaluation Procedures, Second Edition (Ref. 3) provides considerable information on various hazard evaluation techniques that may be employed. Evaluating hazards affecting buildings in process plants may be performed as part of a review focused specifically on the siting issue or as part of a more comprehensive review intended to identify and evaluate all facility hazards. 

Adapted from CCPS Guidelines for Hazard Evaluation Procedures (Ref. 3), Table 1.31... 

This chapter provides general information for performing qualitative or quantitative risk assessments on buildings in process plants. For detailed guidance on risk assessment techniques, the user is referred to other CCPS books on this subject, including Reference 3, Guidelines for Hazard Evaluation Procedures, Second Edition, and Reference 4, Guidelines for Chemical Process Quantitative Risk Analysis. 

Askquith, W. and Lavery, K. (1990) Proc. Ind. Jl. (Sept.) 15. Bursting discs—the vital element in relief. AIChemE (1987) Guidelines for Hazard Evaluation Procedures (Center for Chemical Process Safety, American Institute of Chemical Engineers, New York). 

Sample checklists are shown in Tables 4.1, 4.2, and 4.3. A fairly exhaustive checklist appears in Guidelines for Hazard Evaluation Procedures. Appendix B (CCPS, 1992). 

The purpose of a what-if/checklist analysis is to identify hazards, consider the types of accidents that can occur in a process or activity, evaluate in a qualitative manner the consequences of these accidents, and determine whether the safety levels against these potential accident scenarios appear adequate. The what-if/checklist analysis is described in detail in Guidelines for Hazard Evaluation Procedures (CCPS, 1992). 

The Seveso and Duphar accidents could have been avoided if proper containment systems had been used to contain the reactor releases. The proper application of fundamental engineering safety principles would have prevented the two accidents. First, by following proper procedures, the initiation steps would not have occurred. Second, by using proper hazard evaluation procedures, the hazards could have been identified and corrected before the accidents occurred. 

Figure 10-1 Hazards identification and risk assessment procedure. Adapted from Guidelines for Hazards Evaluation Procedures (New York American Institute of Chemical Engineers, 1985), pp. 1-9.

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