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A real-life example of choosing an inherently safer process option



Although choosing an inherently safer alternative may seem straightforward, sometimes what seems to be the most obvious alternative may not provide the best risk reduction. The process designer must maintain a broad perspective to be able to recognize all potential hazards when evaluating design options. All aspects of operation such as start-up, shutdown, utility failure, as well as normal operation should be considered. Choosing the inherently safer option is best accomplished early in the option selection phase of a project. However, recycle back to the option selection phase may be needed if an option is not thoroughly evaluated early in the process. This report reviews a project to supply ammonia to a catalytic reactor. During the course of the project, an “inherently safer” alternative was selected and later discarded because of issues uncovered during the detail design phase. The final option chosen will be compared to (1) the original design and (2) the initial “inherently safer” alternative. The final option was inherently safer than both the original design and the initial “inherently safer” alternative, even though the design team initially believed that it would not be. © 2006 American Institute of Chemical Engineers Process Saf Prog, 2006