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SIL study is one of the safety studies which is carried out to prevent hazards in process industries. Generally SIL study is carried out after the HAZOP study is completed for a project.

Following Studies are carried out by us –

  1. SIL Classification
  2. SIIL Verification
  3. SIl Validation

Process industry is exposed to risks from incidents like fire, explosion, equipment malfunction etc. causing fatalities and/or monetary losses. Safety instrumented systems (SIS) have been used for many years to perform safety instrumented functions (SIF) in the process industries. If instrumentation is to be effectively used for safety instrumented functions, it is essential that this instrumentation achieves certain minimum standards and performance levels.

The Standards IEC 61508 and 61511 and ANSI/ISA-84.00.01-2004 placed many new requirements on the design, selection, installation, operation, and maintenance of instrumented safety systems.

The standard is based on a SIS Safety Lifecycle addressing the associated activities from initial conception through decommissioning. These standards require that a performance target be assigned and verified for each SIF. The performance target is a quantitative target known as the Safety Integrity Level (SIL).

Safety Integrity Level (SIL) is a discrete level (1 to 4) for specifying safety integrity requirements of the SIFs to be allocated to the SIS.


SIL 4 is used for highest risk systems. Each function is assigned a SIL that reduces risk for a specific hazard.

SIL Verification is the quantitative analysis to verify that the SIL target can be met with intended SIS design. SIL Verification includes determination of probability of failure on demand and spurious trip rates. It considers the type of equipment employed, advanced voting arrangements, diagnostics and testing frequency.