Case study: Implementation of the IEC61508 standard on a chemical plant upgrade project

Many chemical plants now rely on automated control and protection systems. Great care must be taken when designing, operating and maintaining these systems to ensure that potential common mode failures are minimised and system reliability is optimised. The new international standard IEC61508 provides a framework for systematically managing the risks associated with these automated systems. In many ways, the standard is a framework which binds existing safety and risk engineering techniques together rather than being a completely new technique. Emphasis is placed on using systematic approaches, compiling comprehensive documentation, making use of multi-disciplinary teams and taking a Lifecycle approach for the project. The IEC61508 standard has been used successfully on several recent projects at the Bradford site which have major accident hazard potential. This paper explains how the standard has been applied to real projects and highlights the areas of the standard which were difficult to implement.