Condition-based and age-based maintenance in a multi-component system with heterogeneous components incorporating imperfect preventive maintenance actions

This paper proposes a hybrid maintenance strategy that combines condition-based and age-based approaches for multi-component systems. The model distinguishes between components that degrade over time and those that do not, as is often the case in real-world systems such as wind turbines or industrial machinery. In this paper, degrading components follow a three-stage degradation process, namely, a delay time model. The three states are good, defective and failed stage. The other type of components does not exhibit any signs of deterioration. For both components that undergo a deterioration process and those that show no signs of deterioration, their failure is self-announcing, and after the failure, the component is replaced correctively. The replacement of a component is an opportunity to perform maintenance on the remaining components. Based on both the condition and calendar age of each component, various maintenance actions can be implemented, including: leaving the component as is, performing imperfect preventive maintenance, performing preventive replacement, or performing corrective replacement. Considering a sequence of costs for each maintenance action, the objective is to choose the best policy so that the expected cost rate is minimized. Since all maintenance actions are performed at the component level rather than at the system level, applying traditional renewal techniques to analyze this system's maintenance becomes challenging. Therefore, semi-regenerative techniques are employed to evaluate the optimal maintenance policy. Numerical examples are provided to illustrate the results.