Integrated Framework for Optimal Maintenance Policy Under the Challenges of Imperfect Maintenance

In modern industrial settings, the inherently complex nature of equipment and systems introduces uncertainty and variability in defining the quality of preventive maintenance (PM) action. Maintenance imperfectness occurs when maintenance activities fail to address all potential issues within the system, which could be due to time constraints, budgetary limitations, lack of resources, or expertise of the maintenance staff, incorrect installation of components, improper calibration of equipment, or using substandard replacement parts. The unpredictability of PM quality creates challenges in effectively optimizing maintenance policies. This paper addresses the underlying problem by developing the optimal preventive maintenance strategies for three maintenance conditions: imperfect PM with maintenance at failure, imperfect PM with minimal maintenance after failure, and a case where only comprehensive PM can identify system failure. The quality of PM intervention is considered a variable quantity, with discrete probabilities assigned to different levels of quality of preventive maintenance interventions. Weibull distribution is used for modelling failure time of equipment. Failure rate PM model is used for modelling in this study. Numerical example is provided to illustrate the proposed models. Assuming Weibull lifetime distributions of equipment’s, results more accurate predictions of maintenance intervals and expected cost rates compared to reported values in literature. The conclusions of this research offer more realistic perspective compared to those reported in prior studies and will guide maintenance managers in determining when to intervene with corrective maintenance and when to recommend preventive maintenance, in situations where imperfect maintenance executions are expected.