ABSTRACT

Unexpected release of toxic, reactive, or flammable liquids and gases in processes involving highly hazardous chemicals have occurred numerous times in industry. The Occupational Safety and Health Administration (OSHA) estimates that losses can be reduced tremendously if proper safety precautions and preparation at job sites are initiated.

Elements of process safety management from both legal and technical viewpoints are discussed. Application of hazard evaluation methodologies to the safe design and operation of potentially hazardous chemical and petroleum processes are demonstrated. These procedures identify the hazards that exist, the consequences that might occur as a result of the hazards, the likelihood that events might take place that would cause an accident with such consequences, and the likelihood that the safety systems and emergency alarms and evaluation plans would function properly and eliminate or reduce the consequences.

System application of Preliminary Hazard Analysis, What If Analysis, Fault Tree Analysis and Hazard and Operability Analysis are discussed. Elements of OSHA's Process Safety Management Standard are also discussed. This OSHA standard contains requirements for preventing or minimizing the consequences of catastrophic releases of toxic, flammable, reactive, or explosive chemicals.

INTRODUCTION

The advent of complex and high-energy hazardous processes has made process safety management an integral element of process design and operation. Catastrophic events such as Flixboro explosion, Seveso Dioxin release and Bhopal toxic plume release, and a host of others are examples of disasters which could have been prevented by proper application of process safety management techniques. The Flixboro event showed the importance of proper controls when administering changes in plant design such as engineering verification of changes and effects of vapor cloud explosion. The Bhopal event showed the importance of maintenance and administrative controls.

The major objective of process safety management is to prevent unwanted releases of hazardous chemicals especially into locations, which could expose employees and others to serious hazards. An effective process safety management program requires a systematic approach to evaluating the whole process. Using this approach the process design, process technology, operational and maintenance activities and procedures, non-routine activities and procedures, emergency preparedness plans and procedures, training programs and other elements which impact the process are all considered in the evaluation. The various lines of defense that have been incorporated into the design and operation of the process to prevent or mitigate the release of hazardous chemicals need to be evaluated and strengthened to assure their effectiveness at each level. Process safety management is the proactive identification, evaluation and mitigation or prevention of chemical releases that could occur as a result of failures in process, procedures or equipment.

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