PLC-Implementation of Emergency Shut-Down Systems

Abstract

The task of safeguarding systems is to bring processes from dangerous into safe states. A special class of safeguarding systems are emergency shut-down systems (ESD), which, until now, are only implemented in inherently fail safe hard wired forms. Despite their high reliability, there is an urgent industrial need to replace them by more flexible systems. Therefore, a low complexity, fault detecting computer architecture was designed, on which a programmable logic controller for ESD applications can be based. Functional logic diagrams, the traditional graphical specification tool of ESDs, are directly supported by the architecture as appropriate user oriented programming paradigm. Thus, by design, there is no semantic gap between the programming and machine execution levels enabling the safety licensing of application software by formal methods or back translation. The concept was proven feasible by a working demonstration model.