What is the difference between SIL 1 2 and 3?
What Is the Difference Between SIL 1, SIL 2, SIL 3, and SIL 4?
Defined criteria, Safety Integrity Levels (SIL) measure the degree of risk reduction a Safety Instrumented Function (SIF) offers inside a safety system. From lowest to highest, SIL 1 to SIL 4 reflect rising degrees of reliability and safety performance. The severity of possible risks, probability of occurrence, and the system’s capacity to identify and reduce failures all influence the choice of a certain SIL level.
- SIL 1 SIL 1 applies to systems needing just fundamental safety functions where low-level threats exist. It’s appropriate for uses like food processing or building automation.
- SIL 2 Used in chemical, pharmaceutical, and power generating industries, SIL 2 calls for more stringent testing and moderate risk reduction.
- SIL 3 deals with high-risk settings, such nuclear power or oil & gas, where system failure might have grave effects.
- SIL 4 The most strict SIL 4 is set aside for very vital uses like aerospace and defense, where failure is unacceptable.
Outlined in the table below, every level relates to a specified Risk Reduction Factor (RRF) and Probability of Failure on Demand (PFD).
SIL Level Comparison Table
| SIL Level | Risk Reduction Factor (RRF) | PFD Range (Low Demand) | Typical Applications |
|---|---|---|---|
| SIL 1 | 10 – 100 | 1.0E-1 to 1.0E-2 | Food processing, building automation |
| SIL 2 | 100 – 1,000 | 1.0E-2 to 1.0E-3 | Power plants, pharmaceuticals, chemical processing |
| SIL 3 | 1,000 – 10,000 | 1.0E-3 to 1.0E-4 | Oil & gas, nuclear power, petrochemical plants |
| SIL 4 | 10,000 – 100,000 | 1.0E-4 to 1.0E-5 | Aerospace, defense, critical nuclear systems |