Introduction

SIL Verification is a formal assessment performed to confirm that Safety Instrumented Functions (SIFs) are designed and implemented to achieve their required Safety Integrity Level (SIL), as defined during SIL determination or LOPA studies.
It evaluates whether the overall safety instrumented system – including sensors, logic solvers, and final elements – meets the target reliability in accordance with standards such as IEC 61511.

Purpose

• Verify that each SIF achieves the required SIL target
• Assess the reliability of safety instrumented system components
• Calculate Probability of Failure on Demand (PFDavg)
• Confirm adequacy of architecture, redundancy, and proof testing intervals
• Identify gaps between design performance and required risk reduction
• Ensure compliance with functional safety standards and company requirements

Outcomes

• Calculated PFDavg for each SIF and comparison with SIL targets
• Validation of SIF architecture and reliability performance
• Identification of gaps or non-compliance with SIL requirements
• Recommendations for design improvements (e.g., redundancy, component selection, testing frequency)
• Optimized proof test intervals and maintenance strategies
• Compliance with IEC 61511 and functional safety lifecycle requirements
• Structured SIL Verification report ensuring traceability and audit readiness