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IEC 61508: Wikis


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IEC 61508 is an international standard of rules applied in industry. It is titled "Functional safety of electrical/electronic/programmable electronic safety-related systems".

IEC 61508 is intended to be a basic functional safety standard applicable to all kinds of industry. It defines functional safety as: “part of the overall safety relating to the EUC (Equipment Under Control) and the EUC control system which depends on the correct functioning of the E/E/PE safety-related systems, other technology safety-related systems and external risk reduction facilities.”

The standard covers the complete safety life cycle, and may need interpretation to develop sector specific standards. It has its origins in the process control industry sector.

The safety life cycle has 16 phases which roughly can be divided into three groups as follows: phases 1-5 address analysis, phases 6-13 address realisation and phases 14-16 address operation. All phases are concerned with the safety function of the system. The standard has seven parts. Parts 1-3 contain the requirements of the standard (normative), while 4-7 are guidelines and examples for development and thus informative.

Central to the standard are the concepts of risk and safety function. The risk is a function of frequency (or likelihood) of the hazardous event and the event consequence severity. The risk is reduced to a tolerable level by applying safety functions which may consist of E/E/PES and/or other technologies. While other technologies may be employed in reducing the risk, only those safety functions relying on E/E/PES are covered by the detailed requirements of IEC 61508.

IEC 61508 has the following views on risks:

  • zero risk can never be reached
  • safety must be considered from the beginning
  • non-tolerable risks must be reduced (ALARP)

See also

External links




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