Study on Operative Reliability of Safety-Related Control Systems

Abstract

This paper concerns the function of safety devices for machines and their validation according to the standards. The purpose of this study is to understand core concepts included in them through a case-study. In this paper, 3 typical circuits for safeguards are focused and their safety functions are analyzed by ETA and importance index. Through this study, following points are shown: (1) importance of failure detection especially in Category 4, and (2) ranking of components by importance index. Adding to these, the difference in behaviour of safety-relay under certain failure condition is reported.