What is a Safety Instrumented System (SIS)?

A Safety Instrumented System (SIS) is a system designed to take a process to a safe state when predetermined conditions are violated. It consists of sensors, logic solvers, and final elements that detect hazardous conditions and automatically take action to prevent or mitigate accidents. SIS operates independently from the Basic Process Control System (BPCS) and is designed with higher reliability and integrity. Examples include Emergency Shutdown Systems (ESD), Fire and Gas detection systems, and Burner Management Systems.