What is a Safety Instrumented Function (SIF)?

A Safety Instrumented Function (SIF) is a specific safety function implemented by the SIS to achieve or maintain a safe state of the process. Each SIF has a defined set of actions to take when a hazardous condition is detected. For example, closing a shutdown valve when high pressure is detected, or stopping a pump when low flow occurs. Each SIF has an assigned SIL level based on the risk reduction required, and includes sensors (detecting hazard), logic solver (processing), and final elements (taking action).