Managing the risk of continued operation with out‐of‐service safety instrumented system devices

Abstract Safety instrumented systems (SIS) are used to reduce the frequency of hazardous events in the process industry. When SIS equipment has a detected failure or requires online maintenance, the processing facility must decide whether to continue operation or shut down. Continued operation can pose risks beyond what was deemed acceptable as per the company's risk criteria. Understanding the peak risk is important to ensure that all stakeholders are aware of the risk and have compensating measures that ensure continued safe operation until the SIS equipment is returned to service. The paper proposes using Peak Risk Analysis (PRA) to identify unacceptable risks and to document the compensating measures required to support continued safe operation with out‐of‐service SIS equipment.