Use of Risk Methods and Analysis in Plant Systems Design Standard

Abstract The ASME Plant Systems Design Standard (PSD-1) under development provides requirements and guidance for design processes, methodologies and tools that will enable designers to provide safer and more efficient designs with quantified risks. The Plant Risk Evaluations (PRE) include hazard identification and evaluation of hazardous event sequences, including their likelihoods and consequences. Evaluations are included to address both health, safety, and environmental (HSE) risks as well as production risks. Production and HSE risks include the impact of the unavailability of both safety-related and non-safety related components. A structure, system or component (SSC) can be unavailable due to involuntary sources such as component running failures; or the SSC can be unavailable from a voluntary source such as planned inspection, testing, or maintenance. Systems are evaluated and events that could make them unavailable to perform their safety and production functions are characterized. HSE and production risks are characterized and compared to established risk and production objectives and targets. Where objectives or targets are not met, recommendations for additional barriers to mitigate or avoid undesired events are identified to the responsible organization (RO) for the design. The final output of these risk evaluation activities is a listing of availability targets that are inputs to design. This paper describes the functional level design approach and the structure of the PSD-1 requirements and guidance.