Which standard family governs the reliability targets for SIFs?

• A. IEC 61508/62061
• B. ISO 9001
• C. ISO 14001
• D. IEC 62304

Answer: (A)

Reliability targets for a Safety Instrumented Function are defined by the functional safety framework in the IEC 61508 family, which provides the rules for Safety Integrity Levels and how to apply them to safety-related systems. This framework sets how risky a process must be reduced and how the SIF must perform to meet that reduction, including how to select, verify, and maintain the required level of safety throughout the lifecycle. IEC 62061 is part of this family and adapts the 61508 concepts specifically for machinery safety, ensuring the same reliability targets are achievable in that context.

The other standards listed don’t establish these reliability targets for SIFs. ISO 9001 focuses on quality management systems, ISO 14001 on environmental management, and IEC 62304 on the software life cycle for medical devices. They address different concerns and do not define the safety integrity framework used to set SIF reliability targets.