Optimal preventive maintenance policy with the resort to two repair teams with different efficiencies

This paper deals with a periodic preventive maintenance strategy applied to a single-unit system prone to random failures. Planned preventive maintenance actions are perfect and repairs are imperfect following a decreasing quasi-renewal process. Repairs can be performed by either one of two different maintenance teams, one being more experienced and consequently more efficient than the other but more costly. Two decision variables are considered, namely the PM period, T, and the kth repair, during a PM period, after which the repair team should be changed. The performance criterion adopted is the average total cost per time unit which must be minimized. The existence of an optimal solution in terms of the PM period is proved and a mathematical model and a numerical procedure are developed in order to find the optimal policy for any given situation. Numerical examples are presented and the obtained results are discussed.