Working together for a Safer World


Safety Integrity is defined as “The probability of a Safety Instrumented Function (SIF) satisfactorily performing the required safety functions under all stated conditions within a stated period of time”. In simple words, SIL defines probability of a safety instrumented function working correctly when needed.

At Sigma-HSE, we help our customers to cover all four aspects of functional safety assessment as mentioned below:

SIL Classification is required to determine the SIL requirements for Safety Instrumented Functions (SIF). This involves determining the necessary risk reduction required to meet the tolerable risk for specific hazardous scenarios. SIFs can be classified using three techniques specified by IEC 61511 i.e. Risk Matrices (Semi Qualitative), Risk Graphs (Qualitative) and Layer of Protection Assessment - LOPA (Quantitative)

Safety Requirement Specification (SRS) development includes specifying all requirements of SIF needed for detailed engineering and process safety information purposes.

SIL Verification involves demonstrating that the SIF meets the requirements of particular SIL level identified by SIL classification study.

SIL Validation involves validation of the installed SIF. In SIL Validation, SIF is called in demand for multiple number of times to check its performance on the basis of number of recorded failures. For validation, achieved failure rate shall match the SIF verification results.

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