IEC 61508

IEC 61508 is an international standard for the development of electrical, electronic and programmable electronic (E / E / PE) systems that perform a safety function. It is published by the International Electrotechnical Commission (IEC).

The standard consists of seven parts and is entitled " Functional safety of electrical / electronic / programmable electronic systems." It was first published in 1998, of which some parts have been republished in a revised version in 2000. Since 2010 there is a new version, which is also present in the German translation since February 2011. By the European Committee for Standardization ( CEN), the standard in 2001, the same content as EN 61508 has been adopted. In Germany she worked as a German version under the name of DIN EN 61508 and VDE 0803 validity, their use is voluntary.

Objective

The application of the standard in business is mainly driven by the product liability law and the application of the standard, the manufacturer can demonstrate the product liability trial that he has applied an accepted method for risk assessment and for safe product development and manufacturing. The aim is to produce only products that signify possible no health risk or death to the user. The standard now describes how and which aspects are already taken into account at the beginning of development, such as the product structure should be designed ( for example, single-channel or multi-channel systems ), which activities are necessary, are like to document these activities and that all decisions in the internal documentation of the manufacturer must be laid down traceable to his product.

In practice, more and more companies require their suppliers to demonstrate the development and production of their products in accordance with this or a comparable standard (eg ISO 26262 in the automotive sector ) in order to be qualified by the purchase of the company as a supplier. Especially in Germany according to § 4 applies ProdHaftG that the manufacturer of the end product itself is then taken in both the liability (as with any brand damage ) in joint liability if the polluter was only a subcontractor.

The standard generally assumes that there is no way to make a product so that it always works properly diagnosed or own errors and reacts to it. Depending on the degree of risk caused the product in its range of application, however, the demands on measures for fault avoidance, fault control and the required documentation.

Important point of the normative recommendations are in addition to the documentation and reviews in which the documents developed are checked independently to form and content. Again, the degree of independence of the degree of risk depends.

Scope and coverage

The standard can on all safety-related systems, electrical, electronic or programmable electronic components ( E / E / PES ) and their failure means a grave risk to humans or the environment, are used. However, it is not harmonized in accordance with the New Approach in the EU. Therefore, they can not contribute as a presumption of conformity with the European Directives. It does not relate to specific applications. Systems that perform, on request, a safety function, for example the anti -lock braking system in a motor vehicle, and systems that rely on constant execution of the safety function, for example, the control unit of a carrier rocket. According to the standard form, the functions of safety-related systems, the functional safety of the whole system. IEC 61508 is shown as " basic safety publication ," meaning they can be used as a basis for application-specific standards are used.

The following published or in-process standards provide the implementation of the IEC 61508 for a particular application area is:

• IEC 61511: Functional safety - Safety instrumented systems for the process industry
• IEC 61513: Nuclear power plants - Instrumentation and control for systems important to safety - General System Requirements
• EN 50128: Railway applications - Communication, signaling and processing systems - Safety related electronic systems for signaling
• IEC 62061: Safety of machinery - Functional safety of safety- related electrical, electronic and programmable electronic control systems
• IEC 60601-1: Medical electrical equipment - General requirements for safety
• ISO 26262: Road vehicles - Functional safety

The scope of the standard covers design, planning, development, implementation, commissioning, maintenance, modification through to decommissioning and removal of both the risk of causing system as well as the safety-related ( risk reduction ) systems. The standard refers to the totality of these phases as " overall safety life cycle."

Key terms

An element is the determination of the safety integrity level ("Safety Integrity Level" - SIL, there is SIL 1 to SIL 4). This is a measure of the necessary risk-reducing effectiveness and reached the safety functions. If no security-related requirements apply, the development in accordance with the normal standards of the company's quality management system is (referred to in the standard by QM ) perform. The minimum requirements of the standard provides SIL 1 If, after the development of safety-related systems can be shown that for the safety functions requirements for a SIL are met, the SIL is a measure of the effectiveness of safety functions. Since the effectiveness can be achieved both by the reliability of the implementation of the safety function in the event of danger, as well as by immediate shutdown of the dangerous causing systems in the event of an error detection in safety-related systems outside of hazardous situations must not be spoken only of " reliability " of the safety function, which is why the " safety integrity " was introduced as a concept of art.

The required SIL can be determined by a hazard and risk analysis. SIL 4 in this case represents such a high assurance level that it is not relevant in practice in some areas, such as in the area of ​​safety of machines or cars.

And PFD ( probability of dangerous failure on demand - Probability of failure on demand) - The essential parameters for the reliability of the safety function of equipment the calculation basis for PFH ( probability of failure per hour probability of dangerous failure per hour ) will be delivered. The former refers to high-demand systems, ie those with a high request rate, the latter on low-demand systems, are virtually non- operated time -of-life. From these parameters, the SIL can be read. Furthermore, the SFF is introduced (Safe Failure Fraction ), a measure of what portion goes all the possible error in the safe direction. The IEC 61508 covers the simpler applicable EN ISO 13849-1 almost completely with from when it comes to the performance level ( PL) of a device. A SIL can be translated directly into a PL. However, only the first error 61508 viewed within an FMEA in error must conform to IEC, so that Category 4 (according to EN ISO 13849-1), which guarantees a two- fault safety, only by using the procedures according to the EN ISO 13849-1 shall be demonstrated.

Standardization

The standard EN 61508 "Functional safety of electrical / electronic / programmable electronic systems " consists of the following parts:

• Part 0: Functional safety and IEC 61508 (IEC / TR 61508-0:2005-10 )
• Part 1: General requirements ( IEC 61508-1:1998 Corrigendum 1999)
• Part 2: Requirements for safety-related electrical / electronic / programmable electronic systems (IEC 61508-2:2000 )
• Part 3: Software requirements (IEC 61508-3:1998 Corrigendum 1999)
• Part 4: Definitions and abbreviations (IEC 61508-4:1998 Corrigendum 1999)
• Part 5: Examples for the determination of safety integrity levels ( safety integrity level ) (IEC 61508 - 5:1998 corrigendum 1999)
• Part 6: Guidelines for IEC 61508-2 and IEC 61508-3 (IEC 61508-6:2000 )
• Part 7: Overview of techniques and measures ( IEC 61508-7:2000 )

These standards were published in Germany, Austria and Switzerland as a national standard, prefixed by marking DIN, OVE / ÖNORM or SN. There are newer Rework drafts of June 2009 to the standards listed above numbers.

The latest version of IEC 61508, the Edition 2.0, was released on 30 April 2010. In Germany this was held by the DKE - body 914.