Optimal Inspection Policy for a Three-Stage System Considering the Production Wait Time

Inspection is usually carried out periodically to update a system state such that the optimal maintenance policy can be determined. In order to obtain the best inspection and maintenance policy, existing research is focused on improving the modeling accuracy of the system failure process. Little work has been devoted to making full use of the system idle time, which is known as the production wait in production systems. In this research, the failure process of a single-unit system is modeled in three stages with consideration of its production wait time. The objective of minimizing the long-run average maintenance cost per unit time is achieved by finding the optimal length of the periodic inspection interval and renewal age for this single-unit system. By comparing this model with two two-stage inspection models, the numerical study of a real steelmaking converter confirms both the accuracy and effectiveness of the proposed inspection and maintenance model. Furthermore, the sensitivity analysis of different parameters is conducted to explore the optimal choice of maintenance strategy for different cost parameters and degradation parameters. The analysis provides useful management insights for decision-makers.