Dedicated maintenance and repair shop control for spare parts networks

TL;DR

This paper models a repairable spare parts inventory system with a dedicated repair shop, analyzing trade-offs in maintenance strategies and capacity planning for optimal system performance.

Contribution

It introduces a novel queuing network model for a repairable inventory system with age-based replacement and capacity decisions, providing closed-form steady-state solutions.

Findings

Derived closed-form steady-state distribution for the queuing model.

Provided performance measure approximations for multiple capital goods.

Highlighted trade-offs between maintenance thresholds and repair capacity.

Abstract

We study a repairable inventory system dedicated to a single component that is critical in operating a capital good. The system consists of a stock point containing spare components, and a dedicated repair shop responsible for repairing damaged components. Components are replaced using an age-replacement strategy, which sends components to the repair shop either preventively if it reaches the age-threshold, and correctively otherwise. Damaged components are replaced by new ones if there are spare components available, otherwise the capital good is inoperable. If there is free capacity in the repair shop, then the repair of the damaged component immediately starts, otherwise it is queued. The manager decides on the number of repairables in the system, the age-threshold, and the capacity of the repair shop. There is an inherent trade-off: A low (high) age-threshold reduces (increases) the probability of a corrective replacement but increases (decreases) the demand for repair capacity, and a high (low) number of repairables in the system leads to higher (lower) holding costs, but decreases (increases) the probability of downtime. We first show that the single capital good setting can be modelled as a closed queuing network with finite population, which we show is equivalent to a single queue with fixed capacity and state-dependent arrivals. For this queue, we derive closed-form expressions for the steady-state distribution. We subsequently use these results to approximate performance measures for the setting with multiple capital goods.