Evaluation of Maintenance Policies using Markov Chains and Fault Tree Analysis

Reliability analyses of multi-component systems can often be refined by combining Markov-chain models for detailed component characterizations with fault-tree evaluation techniques for describing over-all system behavior. A difficulty encountered in the application of this combined approach is that component maintenance policies can induce statistical dependence among component failures. Thereby, straightforward evaluation of overall system characteristics based upon the assumption of statistically independent component failures can lead to erroneous conclusions. This paper examines the effect of dependent component failures, as induced by the component maintenance policies, on system performance; and it demonstrates that for certain types of maintenance policies (when component maintenance is independent of the condition of the other system components), meaningful results can be obtained by assuming the independence of component failures. The feasibility of the proposed approach is illustrated through a maintenance scheduling problem in nuclear engineering practice.