Understanding Safety Integrity Levels (SIL)

Safety Integrity Levels (SIL)

To better understand SIL, it’s first important to understand Safety Instrumented Systems (SIS). SIS is an engineered system of hardware and software applied specifically for critical process systems. Critical process systems are usually defined as a system that needs to have a reserved “safe state” should a problem arise during operation. Some examples are steam pressure, critical water level, and burner control. Specific control functions are known as Safety Instrumented Functions (SIF) and SIL is a measurement the SIF performance.

SIL-2 and SIL-3-rated
toxic gas monitor 

Safety integrity level (or SIL) is often used to describe process safety requirements. However, there are often misconceptions or misunderstandings surrounding SIL. While the general subject, functional safety and SIL, can be highly technical, the general ideas can be distilled down to a few readily understandable concepts. A basic understanding is imperative to understand why it is important, what certification means, and the implications and benefits of that certification to the end user.

The following white paper, courtesy of Scott Safety, provides an excellent understanding of why SIL is important and how it is beneficial.

Understanding Safety Level Integrity Levels (SIL) from Power Specialties, Inc.