Optimal spare ordering policy for preventive replacement with age-dependent minimal repair under cost effectiveness criterion

This paper develops a preventive replacement policy of spare ordering with age-dependent minimal repair and general random repair costs under cost effectiveness criterion. The spare unit for replacement is available only by order and the lead time for delivery the spare due to regular or expedited ordering follows general distributions. Introducing costs due to ordering, repairs, downtime and replacements, as well as the salvage value of system, we derive the expected cost effectiveness per unit time in the long run as a criterion of optimality. There exists a finite and unique optimum policy of ordering time which maximizes the expected cost effectiveness.