Modelling quality in replacement and inspection maintenance

Heterogeneity in component and maintenance quality is considered in the context of age-based inspection and replacement for a single component system. A three-state component failure model is assumed, with a defective state preceding the failed state. Heterogeneity in maintenance intervention is modelled by supposing that inspections may induce the defective state. Component heterogeneity is modelled by supposing that the population of components comprises a mixture of the weak and strong, and that the mixing proportion and cost of components vary between suppliers. Within this framework, the impact, on system reliability and cost, of switching component or maintenance supplier is determined. Broadly, our finding is that one is much more inclined to switch supplier in order to obtain higher quality maintenance than to obtain higher quality components. A gas pressure control valve is used to illustrate our ideas. ► The maintenance cost and reliability of a simple system are related to the quality of inspection and of replacement components. ► The system can be in one of three states: good, defective or failed. ► Component lifetimes follow a mixture. ► The mixing parameter and the rate of defect induction at inspection are surrogates for the quality of maintenance intervention. ► This approach allows supplier choice in preventive maintenance to be modelled.