Analyzing Chemical Process Safety Systems

As the previous ehapter discussed nuelear power reactor operation and how to perform a PSA on it, this chapter attempts to apply a similar framework to chemical processing. The problem is the diversity of chemical processing that blurs the focus. This chapter begins by showing that accidents in the chemical process industry cost lives and dollars. Descriptions of deadly chemical accidents arc presented to show the chain of sequences that were involved to suggest how their PSA may be structured. Background on selected hazardous chemical process is presented followed by descriptions of how their PSA have structured. The chapter concludes by applying FTAPSUIT to a pressure vessel rupture analysis. 

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A chemical engineer may have a choice of inherent safety variables, such as quantity stored or process temperatures and pressures, or process safety measures such as emergency isolation valves or containment systems, all of which may greatly reduce the vulnerabilities or the consequences of intentional loss. These are in addition to traditional security measures, which may include physical security, background checks, administrative controls, access controls, or other protective measures. For a more complete discussion of the options, refer to the AIChE Center for Chemical Process Safety Guidelines for Analyzing and Managing the Security Vulnerabilities of Fixed Chemical Sites and other references.f... 

In the strictest sense, system safety encompasses process safety and the two are inextricably linked. Since systems are defined to include processes, process safety may be considered a subset of system safety. The application of appropriate system safety tenets to the chemical process industry follows. In the process industry, the system safety practitioner continues his or her quest to identify, evaluate, analyze, and eliminate or control hazards throughout the life cycle of the process (in this case). The precedence of controls remains the same. So, there is a close relation between system and chemical process safety and the process industry. 

Are there documents that provide comprehensive analysis of all potential safety and health hazards of the worksite Are there documents that provide both the analysis of potential safety and health hazards for each new facility, equipment, material, or process and the means for eliminating or controlling snch hazards Does documentation exist outlining the step-by-step analysis of hazards in each part of each job, so that yon can clearly discern the evolution of decisions on safe work procedures If complicated processes exist, with a potential for catastrophic impact from an accident but low probability of such accident (as in nnclear power or chemical production), are there documents analyzing the potential hazards in each part of the process and the means to prevent or control them If there are processes with a potential for catastrophic impact from an accident but low probability of an accident, have analyses such as fault tree or what if been documented to ensure sufficient backup systems for worker protection in the event of multiple control failures ... 

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