Joint optimization of condition-based maintenance and spare parts orders for a two-unit system

Both preventive maintenance and spare parts replenishment affect the system availability and total operation cost. Therefore, joint optimization of maintenance and spare parts orders is a research topic of practical significance. Most existing studies assume that corrective maintenance can only be taken at fixed inspection points, and the base-stock policy was often adopted. This paper investigates the optimal condition-based maintenance and spare parts inventory policy for a two-unit system considering immediate corrective maintenance. The joint optimization problem is formulized as the Markov decision process that are solved by the policy iteration. Numerical study shows that the proposed policy can reduce the long-run expected cost by 9.2% compared with the parameterized policy derived by the genetic algorithm. The structure of the optimal policy is also analyzed and discussed.