Effective SIS solutions: How Emergency Shutdown and HIPPS within SIS can meet IEC and ISA International Standards

摘要

Safety Instrumented Systems (SIS) play a critical role for industrial plants of all types throughout the world in that they prevent or reduce hazardous events by taking the process within that plant to a safe state when predetermined conditions are violated. A SIS typically includes the design and implementation of a variety of shutdown and/or blowdown valves. The three key components of a SIS are: 1) sensors or initiators that detect process conditions; 2) a logic solver that processes an input from the sensors to an output to the final elements; and 3) final elements that perform corrective actions by bringing the process to a safe state. An Emergency Shutdown Valve (ESDV) is the SIS Final Control Element. The Valve/Actuation Package is the weakest link in the Safety Instrumented Function (SIF), contributing greater than 50 percent of total Probability of Failure on Demand (PFD) for an SIF. The reliability, safety, and design of the final element has a significant impact on the overall Risk Reduction Factor. See Figure 1. Upgrading the SIS with a special focus on the Emergency Shutdown and High Integrity Pressure Protection subsystems can significantly improve both plant safety and reduce false trips. Emergency Shutdown Systems (ESD) and High Integrity Pressure Protection Systems (HIPPS) are two of several critical subsystems of a SIS - some others being Gas Systems (FGS), Instrumented Protective Systems (IPS), and Burner Management Systems (BMS).