2. What are the normative and regulatory references (standards related to SIL)?

IEC 61508 is a set of rules and recommendations designed to define electrical, electronic or programmable electronic (E/E/EP) safety systems. It proposes a probabilistic approach based on analysis of the risk which the RIS is designed to counter.

An E/E/EP system comprises all the elements of a system that are required to perform a safety instrumented function, i.e. from the sensor, through the processing logic, to the final element.

This standard is primarily aimed at suppliers of equipment intended for use in RIS systems, i.e. sensors (pressure, temperature, etc.), detectors (gas, flame, etc.), processing logic (safety PLC, fire/gas control unit, etc.) and final components such as solenoid valves, isolation valves, etc. IEC 61508 comprises seven chapters:

• Part 1: General design requirements...