Comprehensive Analysis on Safety and Reliability of Safety-Related Systems Considering Common Cause Failure

Abstract

The common cause failure (CCF) has severe impacts on the safety and reliability of the system, and is the main cause of dangerous failure or function failure. The risk of CCF can be effectively reduced by adopting proper redundancy architectures in the design of safety-related system. In this paper, several common L-channel $M$ -out-of- $N$ parallel redundancy architectures are chosen for study. Firstly, the formulas of the redundancy architectures' safety and reliability indicators are derived respectively, and then the indicators are comprehensively analyzed. Secondly, by comparing the PFH and failure rate of the independent failure parts between that of the CCF parts of the single-channel architecture separately, it is verified that the CCF is the crucial cause of the system failure. Finally, through comprehensively analyzing the PFH and failure rate of all the redundancy architectures, it shows that the overall performance of the four-channel 2-out-of-4 architecture is optimal.