Account for Engineered Systems Properly to Analyze Loss Scenarios

Significant resources are spent by the process industry to minimize losses due to fires, explosions, toxic releases, and equipment breakdown. Risk-based justifications for improvements require the evaluation of the loss scenarios and the needed likelihood and severity reductions. A variety of concepts such as safety barriers, safe guards, safety functions, and protection layers; and many models have been developed and used in this connection. However, these concepts and models may not be conducive to account for all the risk-impacting elements consistently, which is necessary to establish scenario events and scenarios properly. Without proper scenarios, quantification of risk components particularly the likelihood may not be possible; thus, risk-based justifications could be subjective. This paper discusses an approach to identify and account for all the risk-impacting elements in terms of engineered systems, which are the basic building blocks of the process industry. Engineered systems are simply the systems necessary to operate process plants productively and safely; thus, all engineered equipment and facilities (i.e., related to hardware) as well as procedures, and their combinations constitute engineered systems. Losses occur generally when engineered systems fail. Proper identification of engineered systems facilitates identification of proper scenario events and scenarios. Accordingly, the use of engineered systems-based approach to improve the scenario-based analyses necessary for risk assessment in the process industry is promoted.