Defining line replaceable units

Puig, J.E. Parada; Basten, Rob

doi:10.1016/j.ejor.2015.05.065

Cited by 13 publications

(9 citation statements)

References 14 publications

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“…This influences the exchange times, the required resources for the exchange, and the types and amounts of spare parts to stock. Some first results on that problem, without considering spare LRUs and spare assets, can be found in Parada Puig and Basten (2015).…”

Section: Conclusion and Recommendationsmentioning

confidence: 99%

Fleet readiness: Stocking spare parts and high-tech assets

Basten

Arts

2017

IISE Transactions

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We consider a maintenance shop that is responsible for the availability of a fleet of assets; e.g., trains. Unavailability of assets may be due to active maintenance time or unavailability of spare parts. Both spare assets and spare parts may be stocked in order to ensure a certain fleet readiness, which is the probability of having sufficient assets available for the primary process (e.g., running a train schedule) at any given moment. This is different from guaranteeing a certain average availability, as is typically done in the literature on spare parts inventories. We analyze the corresponding system, assuming continuous review and base stock control. We propose an algorithm, based on a marginal analysis approach, to solve the optimization problem of minimizing holding costs for spare assets and spare parts. Since the problem is not item separable, even marginal analysis is time-consuming, but we show how to efficiently solve this problem. Using a numerical experiment, we show that our algorithm generally leads to a solution that is close to optimal and that it is much faster than an existing algorithm for a closely related problem. We further show that the additional costs that are incurred when the problem of stocking spare assets and spare parts is not solved jointly can be significant. A key managerial insight is that typically the number of spare assets to be acquired is very close to a lower bound that is determined only by the active maintenance time on the assets. It is typically not cost-effective to acquire more spare assets to cover spare parts unavailability.

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Section: Conclusion and Recommendationsmentioning

confidence: 99%

Fleet readiness: Stocking spare parts and high-tech assets

Basten

Arts

2017

IISE Transactions

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“…Hence, practice and research explore various system design concepts that enable a reduction of the after-sales costs including downtime and maintenance costs. Such concepts include common components (Briant & Naddef, 2004;Driessen et al, 2017;Thonemann & Brandeau, 2000), reliability and redundancy optimization (Öner et al, 2013;Xie et al, 2014), and a smart design of line replaceable units (LRUs) (Parada Puig & Basten, 2015).…”

Section: Introductionmentioning

confidence: 99%

Optimal design of line replaceable units

Driessen,

de Kruijff,

Arts

et al. 2023

Naval Research Logistics

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A line replaceable unit (LRU) is a collection of connected parts in a system that is replaced when any part of the LRU fails. Companies use LRUs as a mechanism to reduce downtime of systems following a failure. The design of LRUs determines how fast a replacement is performed, so a smart design reduces replacement and downtime cost. A firm must purchase/repair a LRU upon failure, and large LRUs are more expensive to purchase/repair. Hence, a firm seeks to design LRUs such that the average costs per time unit are minimized. We formalize this problem in a new model that captures how parts in a system are connected, and how they are disassembled from the system. Our model optimizes the design of LRUs such that the replacement (and downtime) costs and LRU purchase/repair costs are minimized. We present a set partitioning formulation for which we prove a rare result: the optimal solution is integer, despite a nonintegral feasible polyhedron. Second, we formulate our problem as a binary linear program (BLP). The article concludes by numerically comparing the computation times of both formulations and illustrates the effects of various parameters on the model's outcome.

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“…-In practice, LRU definitions are often made based only on engineering/technical criteria and not by analyzing economic trade-offs from a total LCC perspective [160]. Since improving LRU definitions would require the redesign of the system and the involvement of different actors this decision should be considered as a strategic decision.…”

Section: Lessons Learnedmentioning

confidence: 99%

“…Jensen [161] gives an explicit definition of which item is replaced directly from the asset, and which items are used to repair the failed LRU. In a recent paper, Parada Puig and Basten [160] develop a model for the optimal selection of replacement level within the indenture structure of a technical system.…”

Section: State-of-the-artmentioning

confidence: 99%

“…Most of the related papers focus on defining the best decision on when to replace a particular item and very few papers focus on optimally determining LRUs. The key decision for the LRU definition problem is at what level within the indenture structure of a physical asset to define the LRU, i.e., the decision on what to replace [160]. Jensen [161] gives an explicit definition of which item is replaced directly from the asset, and which items are used to repair the failed LRU.…”

Section: State-of-the-artmentioning

confidence: 99%

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