This paper proposes a maintenance policy for a k-out-of-n: F system operating to fulll several jobs without interruptions. The system is replaced when the N-th job completes or at the k-th failure, whichever occurs rst. So, there are some non-failed components when a replacement is done. These components can be sold as second-hand products to continue working in other systems for a while. The price of them is also considered in the proposed maintenance policy. An optimal maintenance policy is studied to minimize long-run average cost under the constraint of relative mean operating time. Comprehensive numerical studies are done to assess the effect of the model parameters on the optimal solutions. Also, to demonstrate the applicability of the proposed plan, a data set related to wind turbine generator failures is considered as a case study.

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