Maintenance Cost Optimization of Faulty Gearbox under Continuous Vibration Measurement Monitoring

Maintenance management for the gearbox systems aims at reducing the overall maintenance cost and improving the availability of the systems. Since the maintenance costs represent a substantial portion of the total life cycle costs, reliability and maintenance management of the gearbox systems have drawn increasing interests for the reduction of these costs. This paper considers a condition-based maintenance optimization for continuously degrading systems under continuous rotational vibration acceleration monitoring. After maintenance, the states of the system are randomly distributed with residual damage. An optimization technique is used to solve the preventive maintenance problem for faulty (cracked) gear tooth system. The situations where cracked gear tooth system has several ranges of performance levels are considered. To enhance cracked gear tooth system availability, possible preventive maintenance schedules are performed and affect strongly the effective age. Moreover, the technique is used to generate an optimal sequence of maintenance actions providing system working with the desired level of reliability during its lifetime with minimal maintenance cost rate. A single stage gearbox is used for this study, where multi-time tests were carried on healthy and faulty gearboxes individually. The measured and filtered rotational vibration acceleration was collected where hazard lifetime (LT) was determined at failure based on the Weibull distribution with assured reliability. The results indicate that the saving expected costs of either health or faulty gearbox, the basic maintenance cost (C), availability (AV) and maintenance basic cost and availability (CAV) savings have been estimated. On the other hand, the operating time between failure and optimum points for C, AV and CAV savings are all considered.