Preventive replacement in systems with dependent components

A multicomponent series system includes a component which deteriorates over time, changing its operating characteristics and, consequently, increasing the failure rates of neighboring components. Preventive replacement of the deteriorating component can be beneficial. Replacement policies that include inspecting the deteriorating component at system failure instances and replacing it if the deterioration exceeds a critical level, or continuously monitoring the deteriorating component are considered. The system is modeled as a Markov chain solved by an efficient algorithm that exploits the system structure. For a two-component system, a closed-form equation gives the critical level for the minimum-average-cost failure-replacement policy. For the general case, replacement policies are evaluated by mean cost rate and by the ratio of the reduction in the number of failures to the number of preventive replacements