Abstract
In many real production systems, a system may be stopped due to a lack of demand or exhaustion of raw materials. This is known as production wait and provides a good opportunity for maintenance. Meanwhile, the increased complexity of the modern machines brings new challenges for modeling and analyzing their failure behaviors. To address these real-world problems, this article considers a single-unit system that may fail due to either hard failures or soft failures. The wait time of a system is utilized to conduct inspections and maintenance. The system is replaced when a defect is found during an inspection, a failure occurred or a prespecified age threshold is reached, whichever comes first. The cost model, which is the long-run maintenance cost per unit of time, is derived. The optimal periodical inspection interval and the threshold age to minimize the long run maintenance cost per unit of time is then obtained. A case study is conducted to demonstrate the proposed maintenance model. The study shows using the proposed maintenance model can reduce the cost. Sensitivity analysis illustrates how each cost parameter affects the optimal inspection interval and the optimal age threshold.
Highlights
M AINTENANCE is a widely used approach to reduce the operational cost of industrial assets in many sectors such as power grid systems and transportation infrastructure [1]–[4]
We assume the time for age-based replacement is nT, where n is a positive integer. This assumption is frequently used in the literature of maintenance [23], [33], [37], [44]. The novelty of this maintenance model is the consideration of two types of failure modes and utilizing the production wait time to carry out inspection and maintenance
Based on the assumption that the duration of each production wait and the replacement time is negligible compared with the system lifetime, it is reasonable to assume that the replacement cost is the same for: i) replacing the system during periodical inspection, ii) replacing the system when the system reaches the age of Tage, iii) replacing the system during production wait inspection
Summary
M AINTENANCE is a widely used approach to reduce the operational cost of industrial assets in many sectors such as power grid systems and transportation infrastructure [1]–[4]. Hard failures of other components of the subsystem can cause the subsystem to stop working [24] These two examples show that the practical system usually fails due to different types of failure modes. In the literature, there is little research on analyzing how the production wait time can be utilized to conduct inspection or maintenance, especially for complex systems that subject to multiple failure modes. When the system fails or reaches a threshold age, it is replaced Under these assumptions, the long run maintenance cost per unit of time is derived and is minimized to find the optimal periodical inspection intervals and age thresholds. The contribution of this article is three-fold It develops a maintenance cost model for a single-unit system considering two failure modes and production wait time.
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