IEC 61508

IEC 61508 is an international standard published by the International Electrotechnical Commission (IEC) consisting of methods on how to apply, design, deploy and maintain automatic protection systems called safety-related systems. It is titled Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems (E/E/PE, or E/E/PES). IEC 61508 is a basic functional safety standard applicable to all industries. 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 fundamental concept is that any safety-related system must work correctly or fail in a predictable (safe) way. The standard has two fundamental principles: An engineering process called the safety life cycle is defined based on best practices in order to discover and eliminate design errors and omissions. A probabilistic failure approach to account for the safety impact of device failures. 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 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) Part 4 contains definitions Parts 5–7 are guidelines and examples for development and thus informative. Central to the standard are the concepts of probabilistic risk for each 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, associated mechanical devices, or other technologies. Many requirements apply to all technologies but there is strong emphasis on programmable electronics especially in Part 3....