Safety Integrity Level (SIL) quantifies the level of risk reduction provided by a safety function. It relates to the frequency and severity of potential hazards in safety-critical systems.
Key Aspects of SIL:
- Defined by functional safety standards, primarily IEC 61508.
- Ranges from SIL 1 (lowest integrity) to SIL 4 (highest integrity).
- Assesses the probability of failure on demand (PFD) for safety systems.
SIL levels are determined based on:
- Risk assessments that evaluate hazards and their impacts.
- Performance requirements for safety functions.
- Quantitative analysis of system reliability.
The table below summarises SIL levels:
SIL is critical in industries like oil and gas, chemical processing and nuclear power, where safety is paramount.