ABSTRACT
Safety instrumented systems (SIS) play a major part in industrial risk management as risk reduction measures. The main European standard for functional safety of SIS, denoted electrical / electronic / programmable electronic (E/E/PE) safety-related systems, is the IEC 61508 (IEC, 2005a). The second edition will soon be adopted in 2009 (IEC, 2009). Objectives are to enable the design of SIS, and the development of application sector standards. Such examples are IEC 61511 (IEC, 2004) for process industry, and IEC 62061 (IEC 2005b) for machinery. One of the main contributions of IEC 61508 is to consider the overall system and software safety life cycle. The standard framework, with the corresponding normative parts and subclauses, is:
1 development of the overall safety requirements (SR): concept, scope definition, hazard and risk analysis, overall SR specification (Part 1: 7.2-7.5);
2 SR allocation to the designated SIS or other risk reduction measures (Part 1: 7.6);
3 SR specification for each SIS in order to achieve the required functional safety (Part 1: 7.10);
4 realisation phase for SIS design and development in accordance with SR specification, for system (Part 2) and software (Part 3);
5 installation, commissioning, safety validation, including planning (Part 1: 7.8-7.9 and 7.13-7.14);
6 operation, maintenance, modification, and decommissioning (Part 1: 7.7 and 7.15-7.18).
