Modeling and analyzing safety-critical parallel-series system safety

There are working, and two failures states including fail-safe and fail-dangerous in safety-critical systems. This paper studies two different safety-critical parallel-series models by considering their components lifetime distribution possessing general forms. The indices of reliability and safety including the probabilities that the system in these states and mean time for the system under two different failure ways, are derived respectively. Various corresponding indices comparisons between the two different parallel-series system models, and among the series, parallel and parallel-series systems, are conducted. Finally some illustrative numerical examples are employed to show the procedures. The derived indices formulas are without component lifetime distribution assumptions, which have significant meanings for reliability analysis and safety design of the system.