Cumulative Hazard Intensity Based on Sequential Preventive Maintenance Strategy for Ensuring Minimum Reliability

— In designing a preventive maintenance policy, considering only either system reliability or cost may not ensure sustainable system operation because the biased design of a PM policy can result in high maintenance cost and short system life. A PM policy should thus be designed considering a trade-off between system reliability and maintenance costs. PM actions in condition-based maintenance policies are commonly performed at a fixed reliability threshold, which is set high to prevent severe breakdowns. However, it may be difficult to establish cost-effectiveness of a model when the reliability threshold is constrained to be fixed. In this study, a cost-effective PM policy based on a reliability threshold that decreases as the frequency of PM actions increases, is developed, which considers a fixed cumulative hazard threshold while keeping the reliability above an acceptable level. The developed policy was analyzed in two cases; one where the cumulative hazard threshold and one where the predetermined minimum reliability were given as the condition variable, respectively. The results were compared to the model of the fixed reliability threshold, which showed that the proposed PM model led to a lower expected maintenance cost and longer system lifespan. Finally, sensitivity analyses of the condition variables and the maintenance costs were conducted.