What is IEC 61508?

​IEC 61508 is the international standard for functional safety for electrical, electronic and programmable electronic safety related systems.

IEC 61508:2010 was published as Edition 2 in 2010.

Functional safety is the part of the overall safety relating to the equipment under control and its associated control system that depends on the correct functioning of the safety-related system. Functional safety is achieved when all the specified safety functions, of the safety-related system, can satisfy their required safety performance. Functional safety is undertaken by active systems.

We recognise IEC 61508 as the benchmark for achieving functional safety and manageing risks in a proportionate way.

IEC 61508 sets out the requirements for ensuring that systems are designed, implemented, operated and maintained to provide the required safety integrity level (SIL). Four SILs are defined according to the risks involved in the system application, with SIL4 being used to protect against the highest risks. The standard specifies a process that can be followed by all links in the supply chain so that information about the system can be communicated using common terminology and system parameters.

Some organisations or people can find functional safety and IEC 61508 compliance as a daunting prospect. One of the key principles of the Association is to promote and support the best routes for compliance to IEC 61508 and related standards. Please review the CASS webpages and consider joining the Association if you are new to functional safety (join us).

The IEC 61508 standard family is in seven main parts (plus a technical report):

• IEC TR 61508-0, Functional safety and IEC 61508
• IEC 61508-1, General requirements
• IEC 61508-2, Requirements for E/E/PE safety-related systems
• IEC 61508-3, Software requirements
• IEC 61508-4, Definitions and abbreviations
• IEC 61508-5, Examples and methods for the determination of safety integrity levels
• IEC 61508-6, Guidelines on the application of IEC 61508-2 and IEC 61508-3
• IEC 61508-7, Overview of techniques and measures

IEC 61508 has been adopted in the UK as BS EN 61508, with the “EN” indicating adoption also by the European electrotechnical standardisation organisation CENELEC. Other standards are being produced for the application of the 61508 approach to particular sectors.

Sector specific standards related to IEC 61508 include:

• IEC 61511 Process industries
• IEC 61513 Nuclear power plants
• IEC 62061 Machinery sector
• ISO 13849 Machinery sector
• IEC 61800-5-2 Power drive systems
• ISO 26262 Automotive sector

IEC Functional Safety