Software based safeguarding of chemical plants-experiences at the realization of PES application software

摘要

There are many ways to minimize the risk of a critical process. The best way, of course, is to build an inherent safe process. Where this is not possible Safety Instrumented Functions (SIF) will be applied to reduce the risk to an accepted level. Over the last decade fail-safe PLCs (PES - Programmable Electronic Systems) became the first choice for safeguarding critical processes. The range of software intensive systems varies from simple systems for high temperature or high pressure protection to high complex systems with different protection scenarios. Simple systems are easy to manage but complex systems require advanced methods of specification, design, development, documentation, verification and validation. This article deals with the experiences during the specification phase of complex safety-related PES application software associated to the process industry.