A multi-echelon system's simulation model for repairable and consumable items management

Repairable items inventory management is complex and important. On the one hand, complexity is due to a variety of reasons such as system structure, unknown repair times and multi-indenture item configuration. On the other hand, importance is traced since stock determines systems operability. Several multi-echelon inventory models for repairable items have been developed, however even the most recent have restrictions to their successful application. To surpass some of these limitations a simulation model is developed in this work. This not only permits the explicit consideration of hierarchical parts structure but also admits a multi-echelon structure system (three levels). Depending on the failure, reparation can be done at different places and the repair time depends on the components' stock or, if there are none, on the repair time of the missing items. The model establishes a relationship between the system's operability and the stock of the different parts. An (s,Q) or (S-1,S) inventory policy is assumed for consumable or repairable items respectively. The resulting model is quite general where no restrictive assumptions on the cases to model are required.