CONTROL-SYSTEM SAFETY INTERLOCKS - DESIGN AND IMPLEMENTATION

This paper provides an overview of an industrial users methodology for the design and implementation of control and safety systems for interlock applications. The method has been in operation for five years but has been continuously improved by input from, and participation in, various national and international standard bodies and organizations. It is intended to provide a practical and consistent methodology for engineers to apply in the classification and implementation of safety interlock systems (SISs). Event classification is carried out by a team of employees, with diverse experience and job assignments, during a process hazards analysis (PHA). The implementation phase is prescriptive since designs exist for each integrity level that has been certified by plant experience with the scheme and the hardware. Diversity in the SISs is obtained by requiring different technologies for high integrity level solutions.