Definition:
A Safety Instrumented Function (SIF) is a protective function that brings a process to a safe state in response to a specific hazardous condition. Some would call it a “loop”. Many SIFs make up a Safety Instrumented System (SIS). The SIFs are the core building block of a SIS.
Key Points:
- Defined by sensors, logic solvers, and final elements.
- Each SIF must meet an assigned SIL target.
Example:
A high-pressure shutdown loop on a separator vessel is a SIF.
See Also: safety instrumented system (SIS)
Cited Source:
- IEC 61511-1:2016, Clause 3.2.66
- ISA high level SIS article