Joint optimization of maintenance and spares inventory policies for a series system with multiple voting subsystems supported by protective devices

The joint optimization of maintenance and spares inventory policies is a momentous topic in engineering domain due to its benefit for improving the system reliability. Equipping systems with protective devices is another effective way to enhance system reliability which has aroused the research interest of scholars in recent years. However, the joint optimization problem of maintenance and spare parts inventory for systems with protective devices has not been attached importance. Therefore, this paper develops a joint optimization model of maintenance and spares inventory strategies for a series system with multiple voting subsystems supported by protective devices. Internal degradation and external shocks are taken into consideration simultaneously to cause the deterioration of the system and devices. A limited number of repairmen is considered, and (s, S) inventory policy is adopted for protective devices as well as each type of units. By applying the Markov process imbedding approach, system steady probability and relevant reliability probability indices including system availability, spares availability, and repairmen availability are obtained. The objective of developed joint optimization model is to derive the optimal repairmen allocation and spares inventory policies such that the system availability can be maximized while meeting the cost requirement. Finally, numerical examples based on the automobile engine system with cooling systems are presented to validate the superiority of the proposed joint policy of maintenance and spares inventory.