The Effect of Maintenance Quality on Spare Parts Inventory for a Fleet of Assets

This paper considers the effect of fleet size on a joint policy of maintenance and spare parts inventory when spare parts are of varying quality. We consider N identical one-component systems subject to age-based replacement, and with a single echelon periodic review spare-parts policy. The joint policy is optimised with regard to the long-run total cost per unit time, where the cost components include both replacement and inventory related costs. In particular, we are interested in the effect of spare parts quality and the size of the fleet on the variability in the demand for spare parts. Furthermore, the effects of changing lead time, different failure characteristics, and simultaneous deployment of the N systems over a finite horizon on the optimal joint policy are investigated. We develop a stochastic simulation model to investigate these effects. We find that the scale effect varies with the quality of spare parts: the poorer the quality of spare parts, the smaller the scale effect. Our approach allows the value (e.g. cost of poor quality spare parts) in spare parts provisioning for maintenance to be quantified.