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Process safety engineers promote loss prevention by providing recommendations when deficiencies are observed. Deficiencies are undesirable conditions that aggravate the likelihood and/or the severity of loss events. Any improvement needs resources, and since the resources are always limited, process safety engineers have to establish priorities for loss prevention recommendations. One appropriate way to prioritize the recommendations is to evaluate and compare the cost of risk reduction associated with the improvements. While qualitative risk analysis techniques may not be able to provide the necessary resolution to differentiate the improvements, quantitative techniques need much expertise, time, and funds. A feasible approach would be a semiquantitative methodology with the simplifications necessary to make it easy to use, but at the same time providing the needed resolution for prioritization. This article presents such a methodology to prioritize loss prevention recommendations. The methodology uses the concept of engineered systems, which are simply hardware (equipment or facility), procedures, or a combination put in place to serve specific functional intents. The basis of the methodology is founded in the premise that deficiencies are always associated with engineered systems and deficiencies increase their failure likelihoods. A few examples are provided with the details of the methodology and the incorporated simplifications. © 2009 American Institute of Chemical Engineers Process Saf Prog, 2009

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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.