IEC 61508: Foundation for safety

IEC 61508 is an international standard that deals with the safety of electrical, electronic and programmable electronic systems. The standard is applicable to a wide range of industries, including the automotive, aerospace, rail, medical, energy and process industries.

As IEC 61508 has spawned many derived industry-specific standards, it is worth taking a closer look at these.

IEC 61508 specifies requirements for the development process of E/E/PE systems to ensure their safety. The standard defines various Safety integrity level (SIL) and describes the system development requirements needed to achieve these SILs.

Structure of the standard

1. IEC 61508 consists of a total of seven parts. The first part defines the basic principles and terms used in the standard. It also describes the areas of application, the objective and the structure of the standard. This is useful for gaining an overview.
2. This part specifies the requirements for the electrical safety of E/E/PE systems. It contains specifications for avoiding electrical hazards and defines protective measures such as protective conductors, insulation and isolation.
3. The third part focuses on the requirements for the software of E/E/PE systems that are important for safety. It describes the development process for safety-relevant software and specifies requirements for the validation and verification of software.
4. The fourth part is for reference only and defines terms and abbreviations
5. The fifth part is short but extremely useful: it contains guidelines on SIL and concrete examples for implementation.
6. The next appendix is an application guideline and helps to implement the contents of parts 2 and 3 correctly in the company.
7. The value of the final section, application notes on procedures and measures, should not be underestimated. Here we find many practical techniques for specific, recurring topics, from energy supply to ventilation, from redundancy to testing.

IEC 61508 for specific industries

The standard is so important because there are many other standards that are specifically tailored to certain industries and are based on IEC 61508. One example of this is ISO 26262, a standard that focuses on the safety of electrical and electronic systems in motor vehicles.

Below you will find a list of some standards that are based on IEC 61508:

• ISO 26262: This standard is specific to the automotive industry and deals with the functional safety of road vehicles. It provides guidelines for the development of safety-related systems in road vehicles.
• IEC 62061This standard is specific to safety-related control systems used in the field of industrial automation. It outlines the requirements for the development process of safety-related control systems in order to ensure their safety.
• IEC 61511This standard is specific to the process industry and covers Safety Instrumented Systems (SIS). It provides guidance for the design, implementation, operation and maintenance of SIS to ensure safety.
• IEC 61800-5-2This standard deals with safety-related aspects of variable-speed electrical drive systems. It contains guidelines for the design and implementation of safety functions in these systems.
• IEC 62278This standard deals with the development of software for railroad control and safety systems. It contains guidelines for the development process of software used in railroad control and safety systems to ensure safety.
• IEC 62425This standard addresses the requirements for obsolescence management in the procurement, supply and maintenance of products used in industrial process equipment. It provides guidance to ensure safety when replacing obsolete products.
• IEC 61513This standard deals with the design, commissioning and operation of measurement and control systems for nuclear power plants. It contains guidelines for the development process of these systems in order to ensure safety.

There are certainly others, but these are some of the best-known standards based on IEC 61508.

Conclusion: It's worth taking a look every now and then

In practice, most systems engineers will consult the industry-specific standard directly. However, the general standard is useful for internalizing the guiding principles. The standard also helps "industry switchers" to transfer their existing knowledge (e.g. from aviation) to the new industry (e.g. automotive).

Knowledge of IEC 61508 also helps consultants to switch quickly "in their heads" from one sector to another. And the standard is of course recommended for anyone who sees themselves as an expert and simply wants to learn more.

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