Spare Parts Procurement Research Articles

Progressive Hedging Innovations for a Class of Stochastic Resource Allocation Problems

Progressive hedging (PH) is a scenario-based decomposition technique for solving stochastic programs. While PH has been successfully applied to a number of problems, a variety of issues arise when implementing PH in practice, especially when dealing with very difficult or large-scale mixed-integer problems. In particular, decisions must be made regarding the value of the penalty parameter p, criteria for termination, and techniques for accelerating convergence. We investigate these issues in the context of a class of scenario-based resource allocation problem in which decision variables represent resources available at a cost and constraints enforce needs for sufficient combinations of resources. We introduce techniques for selecting p in proportion to the unit-cost of the associated decision variable, a mathematically-based heuristic for setting the p parameter, novel techniques for convergence acceleration, and methods for detecting and recovering from oscillatory behavior. The efficacy of these techniques is empirically assessed on two test cases: a difficult laboratory stochastic network flow problem and a largescale, real-world, robust spare parts procurement planning problem. Both test problems have integer variables in both stages. Additionally, we demonstrate that variable-specific p values are more effective than traditional fixed p values, and that the PH algorithm can serve as an effective heuristic even when the mathematical conditions for convergence are not respected.

Multi-criteria decision making on total inventory cost and technical readiness

XYZ Company spends millions of dollars in the procurement of spare parts and tools every year. The maintenance part plays the role of sustaining the technical readiness of the equipment and vehicles. This research will try to find ways to reduce total inventory cost while maintaining the targeted level of technical readiness. The research consists of two phases of multi-criteria decision making on total inventory cost and technical readiness. First phase is to apply a 2-dimentional material classification technique to the selected data. Thus, a combination of ABC- and 123-analysis is used to simplify the problem by focusing on costly items only. The second phase is to apply a deterministic inventory model to the results of the material classification. A detailed analysis of the technical readiness and total inventory cost is covered for the deterministic inventory model. The objective of this research is to design a new system to balance readiness and the associated total inventory cost by finding the relationship between the desired level of technical readiness and cost. Finally, a comparison between the current inventory system and the proposed one shows around 42% savings in the total inventory cost over a period of 3 years, (Adi in Optimizing total inventory cost and enhancing technical readiness level. Master’s thesis, ESM at AUS, Sharjah, UAE, 2005).

Solar energy trial in Folovhodwe South Africa: Lessons for policy and decision-makers

In Mutale Local Authority of South Africa, a photovoltaic pilot project was commissioned to provide off-grid electricity to 582 households residing in Folovhodwe village. The aim was to try a renewable source of energy supply in a rural settlement area. The Beneficiaries Assessment method was used to assess the problems of the implementation and operation of the solar energy project in Folovhodwe. The project initiators did not realize that there would be the problem of the sustainable implementation of the project. The problem of sustainability was related to the inadequate definition of the role of each stakeholder. For example the end users were not taught how to properly operate and repair faulty equipment because it was not built into the planning and implementation stages of the project. Skill acquisition through capacity building for the end users can promote the sustainability of the project on a long-term basis. In Folovhodwe, improper planning and implementation of the project was responsible for the failure of the project. The project initiators did not foresee the problem of theft of materials, problems related to the procurement of spare parts and who would bear the cost of maintenance of the facilities. The failure of the project was also related to the inability of the policy makers to tackle the question of the role that each stakeholder should play to ensure the success of the project in a rural setting. The suggestion to policy and decision-makers is that pilot projects with relatively new technology input in a rural area should reconsider the importance of culture, capacity development and the level of income of the end users at the initial planning stage and implementation.

Joint inventory/replacement policies for parallel machines

In many manufacturing settings there is a significant cost associated with lost capacity due to machine failures. When this is combined with long lead times on the procurement of spare parts, it is often necessary to maintain inventories of critical machine components. Thus, the maintenance policy for the machines is inherently coupled to the inventory policy for spare parts. In this paper we identify and investigate the relationship between these two policies.

On the implementation of a control-based forecasting system for aircraft spare parts procurement

The implementation of a new control-based forecasting system (SDF) in 1989–1991 at the Aviation Supply Office, Philadelphia, Pennsylvania, is documented. The philosophy, experience, principles and formulas are presented with results from three implementations.

Equipment Qualification: The Process for New Plants as Seen by a Utility

The qualification process, based on the experience an electric utility gained through its efforts to meet the requirements of IEEE Standards 627-80 and 323-1974 and the attendant regulatory guidance for new plants, is presented. Important aspects of each step from initial plant design to maintaining equipment qualification during operations are described. Although all these steps are not directly applicable to near-term and operating plants, the guidance offered is generally appropriate for procurement of qualified spare and replacement parts and for plant modifications of safety systems.

On the Economic Management of Large Organizations: A Laboratory Study

A LARGE fraction of most nations' resources is employed by very large organizations. Moreover, the management of these government agencies and giant private corporations has often been decentralized to such a degree that the numerous component subunits have incompatible objectives. These modern tendencies raise special problems of interest to managers, economists, and other social scientists. The magnitude of the resources used by some of these enterprises-and especially by the military departments of the federal government-is so large that the economist can hardly ignore them; the Air Force budget alone is approximately $17 billion a year, which makes it comparable to the entire automobileproducing industry.' A natural question is whether the economic efficiency of these very large organizations can be increased. Economic management of very large enterprises inevitably encounters problems of intra-firm organization. Of special import are information flows, lines of authority, and decision points within an organization. In very large organizations there will be many subunits that often have conflicting interests, may compete for resources, and prefer autonomy. Even within a single military service, subsidiary Commands can thwart, disregard, and occasionally disobey the directives of higher authority. Such tendencies to internal anarchy mean that it is not enough for management to devise optimum economical policies. These policies must also be implemented, and this requires the development of detailed procedures. More important, taking organizational conflicts into account, these procedures must be such that employees, in their daily work, will be able and willing to follow them. In many respects this is still an unexplored area. However, a number of scientists have recently been devising preferred economical policies for the procurement and distribution of aircraft spare parts by the Air Force. In addition, in an attempt to see whether they are practical, these policies and their attendant procedures were enacted for several months in a laboratory. This experiment simulated, with people and computers, a very considerable part of the Air Force supply system. The present paper seeks to describe the economic problems of supporting aircraft with spares, the policies developed, and the laboratory simulation that assessed them. This subject has some interest in its own right. But another purpose is to present a case study in the use of laboratory representation as a I Some economists are likely to despair of analyzing the economic efficiency of government agencies. It is true that, not knowing the worth of extra activity, the desirable scale of remains uncertain. However, tractable suboptimizations remain, such as producing a given output with minimum cost.

THE INFLUENCE OF CORROSION ON PROPELLER SHAFT MAINTENANCE

In light of our present national emergency, we realize the prime necessity of utilizing every available means to coordinate our maintenance program to meet performance standards of our equipment with the least possible additional load on repair and replacement facilities.With the work loads of propulsion and auxiliary machinery manufacturers increasing daily, the procurement of spare parts presents a problem of growing complexity. This is especially true in respect to parts such as propeller shafts, whose large proportion require relatively long periods of time to complete the manufacturing operations. As facilities for this type of work are limited, serious delays in delivery may be experienced should an emergency arise, requiring extensive and immediate replacements.