An Algorithm for Performance Evaluation of Closed-Loop Spare Supply Systems With Generally Distributed Failure and Repair Times (original) (raw)
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This investigation is concerned with the transient analysis of machine repair problem with M operating units and multi types of warm spares. In case when all spares are being used, the failure of units occurs in degraded fashion. Each unit is assumed to fail in two modes. When all permanent repairmen are busy, the caretaker who brings the failed units for repair departs from the system after waiting for sometime in the queue due to impatience. For transient state, Chapman-Kolmogorov equations governing the model are constructed. Various performance measures such as expected number of failed units in each mode, average number of operating units in the system, average number of idle and busy repairmen in the system, operative utilisation factor, etc., are obtained. The cost minimisation problem to determine the optimum number of spares in terms of various cost elements has been formulated. We used Runge-Kutta technique to find the numerical solution for the transient model. The sensitivity analysis is performed to observe the effect of different parameters on various performance indices.
A Model for Optimizing Repairshop Capacity and Spare Parts Inventory
2010
We develop a new repair shop/spare parts inventory model where transportation times and costs are significant. We consider a system consisting of m manufacturing plants with identical machines at different locations. When a machine fails, the defective component should be repaired in a designated repair shop. This unit can be replaced immediately if a spare part is available. Otherwise, the machine is down until a component is repaired and put back into service. We find the optimal level of spare parts inventory at each location. We study the effect of repair capacity pooling on the total cost of the system. We show that in some cases, repair shop pooling is not cost efficient even if transportation costs are relatively low. We also show at which location the centralized repair shop should be hosted to minimize overall system costs.
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The research in this paper is motivated by a real life spare parts networks for complex technical systems in oil refining sector. At the customers the availability of the installed technical systems often is essential for the primary process. Hence, they require a high availability. For improve the management of the spare parts inventory the main company (the customer) has developed a new strategies for pushing down to the supply echelon some inventory so as to increase availability of finished parts or components while the properties is still kept by the supplier until its usage, so as sharing in such a way the inventory costs. In this paper after reviewing the literature on spare parts management the industrial case is discussed and based on it a model with closed queuing network approach will be shown. Due to its analytically difficultness the optimality of the parameters will be addressed via simulative way.
OR Spectrum, 2007
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Two-echelon spare parts inventory system subject to a service constraint
IIE Transactions, 2004
In this paper, we consider a spare parts inventory problem faced by a manufacturer of electronic machines with expensive parts that are located at various customer locations. The parts fail infrequently according to a Poisson process. To serve customers when a failure occurs, the manufacturer operates a central warehouse and many field depots that stock spare parts. The central warehouse acts as a repair facility and replenishes stock at the field depots. There is a centralized decision maker who manages the inventory in both the central warehouse and the field depots. We develop a continuous review, base stock policy for this two-echelon, multi-item spare parts inventory system. We formulate a model to minimize the system-wide inventory cost subject to a response time constraint at each field depot. We present an efficient heuristic algorithm and study its computational effectiveness.
International Journal of Engineering Research and Technology (IJERT), 2014
https://www.ijert.org/spare-parts-management-for-corrective-maintenance-of-the-complex-system-under-uncertainty-of-failures https://www.ijert.org/research/spare-parts-management-for-corrective-maintenance-of-the-complex-system-under-uncertainty-of-failures-IJERTV3IS120933.pdf Spare part is one of the main factors in the maintainability. Therefore, it is very importance to appropriately supply the spares. If spares are acquired more than necessary then it would make the inventory cost, which is a sunk cost incurred. If insufficient supply of spares, it will cause a lack of spare parts for maintenance actions. And this will result in cost of lost opportunity to make profit during machine stopped while waiting for spares. Importantly, the appropriated purchase and storage of parts in inventory will be helpful to save costs. This study is mainly focused and applied the principle of payoff matrix using for the spare parts' procurement for a number of appropriations. The main idea is to think of the supply for spare parts on the basis of multiple machines with applying these with payoff matrix principle. This study also takes the opportunity cost when machine stopped production in the absence period of spares to be added into the equation. The principle and concept of this study is based on a balance and trade-off between the inventory cost of spare parts and the cost of losing in opportunity. In addition, the raised sample of this research was basically supposed under conceptual of general form which is able to apply this principle to all types of machines.
Effects of finite repair capacity in multi-echelon, multi-indenture service part supply systems
International Journal of Production Economics, 2002
In this paper, we consider multi-echelon, multi-indenture supply systems for repairable service parts with finite repair capacity. We show that the commonly used assumption of infinite capacity may seriously affect system performance and stock allocation decisions if the repair shop utilisation is relatively high. Both for the case of item-dedicated and shared repair shops, we modify the well-known VARI-METRIC method to allocate service part stocks in the network. The repair shops are modelled by (single or multi-class) multi-server queuing systems. We validate our procedure by comparison to results from discrete event simulation. This comparison shows that the accuracy of the technique presented in this article is on average more than five times as close to simulated values as the classical VARI-METRIC technique. r .nl (A. Sleptchenko). 0925-5273/02/$ -see front matter r 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 5 -5 2 7 3 ( 0 2 ) 0 0 1 5 5 -X
REDUCING COSTS OF SPARE PARTS SUPPLY SYSTEMS VIA STATIC PRIORITIES
Asia-Pacific Journal of Operational Research, 2009
We study static repair priorities in a system consisting of one repair shop and one stockpoint, where spare parts of multiple repairables are kept on stock to serve an installed base of technical systems. Demands for ready-for-use parts occur according to Poisson processes, and are accompanied by returns of failed parts. The demands are met from stock if possible, and otherwise they are backordered and fulfilled as soon as possible. Returned failed parts are immediately sent into repair. The repairables are assigned to static priority classes. The repair shop is modelled as a single-server queue, where the failed parts are served according to these priority classes. We show that under a given assignment of repairables to priority classes, optimal circulation stock levels follow from Newsboy-type equations. Next, we develop fast and effective heuristics for the assignment of repairables to priority classes. Subsequently, we compare the performance of the system under these static priorities to the case with a First-Come First-Served (FCFS) service discipline. We show that in many cases static priorities reduce total inventory holding and backordering costs by more than 40%. Finally, we analyse the effect of the number of priority classes.
Using repair priorities to reduce stock investment in spare part networks
European Journal of Operational Research, 2005
In this paper, we examine the impact of repair priorities in spare part networks. Several heuristics for assigning priorities to items as well as optimising stock levels are developed, extending the well-known VARI-METRIC method. We model repair shops by multi-class, multi-server priority queues. A proper priority setting may lead to a significant reduction in the inventory investment required to attain a target system availability (usually 10-20%). The saving opportunities are particularly high if the utilisation of the repair shops is high and if the item types sharing the same repair shop have clearly different characteristics (price, repair time). For example, we find an investment reduction of 73% for a system with single server repair shops with an utilisation of 0.90 that handle five different item types.