Integrity level verification for safety-related functions

Abstract

This article describes methods for the safety integrity level (SIL) verification of safety-related functions with regard to probabilistic criteria given in international standards IEC 61508 and IEC 61511. These functions are realized using the electrical, electronic and programmable electronic (E/E/PE) systems or safety instrumented systems (SIS). Some methods are proposed for quantitative probabilistic modelling taking into account potential dependent failures in redundant systems with diverse channels within subsystems. The analyses of safety-related systems include testing and maintenance planning of subsystems, in particular the sensors and actuators with regard to the probabilistic criteria defined for given SIL. The methods are illustrated on some examples of systems from industrial hazardous plants