A Further Study on Safety of Series and Parallel Systems

In safety-critical systems, there are both dangerous and safe failure states. This paper presents different models of safety-critical systems including series and parallel systems whose lifetime distributions are general forms. Also the reliability aspects are derived such as the probabilities that the system is in working state, fail-safe state and fail-dangerous state, the mean times for the system working, fail-safe and fail-dangerous. Finally some numerical examples are presented to illustrate the results obtained in this paper. These indexes have practical and theoretical meanings for the systems. The derived formulas are new results and can be used regardless of the forms of component lifetime distributions and have significant meaning for evaluating the system safety performance and can also be used to improve the safety design of systems.