Ordering Policies under Minimal Repair

Many maintenance policies in the literature have assumed that whenever a unit is to be replaced, a new unit is immediately available. However, if the procurement lead time is not negligible, an ordering policy should determine when to order a spare and when to replace the operating unit. This paper proposes and analyzes two ordering policies for replacement with minimal repair which include the 'periodic replacement with minimal repair at failure' of Barlow & Hunter as a special case. If the failure rate is monotonic, the objective functions representing the cost rates for the two policies are unimodal.