Joint optimization of bi-level imperfect maintenance and spare parts inventory considering order quantity

The joint optimization of various maintenance actions and the supply of spare parts has received extensive attention in recent years owing to its advantage in reducing the overall operational costs of industrial systems. In this study, a joint optimization model is proposed considering bi-level imperfect preventive maintenance and spare part ordering. A virtual age reduction model that considers bi-level imperfect preventive maintenance (PM) is established. Upon each system shutdown, the PM level is determined based on the cost-effectiveness ratio. Furthermore, an improved (s, S) inventory policy is proposed utilizing the information of the remaining number of PM and accumulated consumption of spare parts. Finally, the joint optimization models consisting of different PM policies and spare parts inventory policies are solved. Case studies show that compared with the traditional (s, S) inventory policy, the proposed joint optimization model can coordinate the ordering quantity of spare parts with the PM policy, and reduce the expected maintenance cost. A sensitivity analysis of the cost parameters is performed to explore their impact on the maintenance economy.