Many safety-related systems that would have used electromechanical technology or solid-state electronics now use programmable electronics .
IEC 61508 covers functional safety of safety-related systems that use electrical and/or electronic and/or programmable electronic (E/E/PE) technologies. The standard applies to these systems irrespective of their application.
An example E/E/PE safety-related system using electrical (or electro-mechanical) technology is the guard interlocking and emergency stopping system for machinery.
Devices such as programmable controllers,
programmable logic controllers (PLCs) and digital communication systems (e.g. bus systems)are part of this trend. Furthermore, enabling technologies, such as application specific integrated circuits (ASICs), microprocessors, and intelligent sensors, transmitters and actuators, are increasingly being integrated into products and systems.
Example applications include crane safe load indicators, variable speed motor drives used to restrict speed for protection, systems for interlocking and controlling the exposure dose of medical radiotherapy machines, or the indicator lights, antilock braking, and engine-management systems on automobiles. Other examples are emergency shutdown systems in hazardous chemical plants, railway signalling systems and fly-bywire operation of aircraft flight control surfaces Recent developments include network based safety-related systems, often facilitated by internet technology.
An exampleis the remote monitoring, operation or programming of a network-enabled water treatment plant. An E/E/PE safety-related system covers all parts of the system that are necessary to carry out the safety function (i.e. from sensor, through control logic and communication systems, to final actuator, including any critical actions of a human operator). An E/E/PE system may be safety-related even if it does not have any direct control over potentially hazardous equipment. For example an information-based decision support tool might be safety-related if erroneous results affect safety.
IEC 61508 as a basis for other standards Parts 1, 2, 3 and 4 of IEC 61508 are IEC basic safety publications. One of the responsibilities of IEC technical committees is, wherever practicable, to make use of these parts of IEC 61508 while preparing their own sector or product standards that have E/E/PE safety-related systems within their scope.
For more details see IEC Guide 104, The preparation of safety publications and the use of basic safety publications and group safety publications and ISO/IEC Guide 51, Safety aspects Guidelines for their inclusion in standards. IEC 61508 is the basis for a published nuclear sector standard. It is also currently being used as a basis for developing other sector standards (e.g. machinery, process) and product standards (e.g. power drive systems). It is therefore influencing the development of E/E/PE safety-related systems and products across all sectors.
Many requirements of IEC 61508, particularly in parts 2 and 3, are not repeated in the application sector or product standards but are referenced instead. The result is that most users will need IEC 61508 also.
The market for any product, component or subsystem that complies with IEC 61508 is potentially very large since in principle they are capable of meeting the requirements of any sector standard based on IEC 61508.
