W.H.M. Zijm

Spare parts management at complex technology-based organizations: an agenda for research

This paper explores the applicability of sophisticated models and techniques for spare parts inventory management within a highly technology-driven environment, viz. the Royal Netherlands Navy. In particular, we discuss the structure of the so-called VARI-METRIC models, a set of tools that has been designed for decision support in spare parts management, initially in a military organization. These tools aim at a high availability of complete technical systems, as opposed to more classical inventory management approaches, that are primarily directed towards a high availability of individual items. Unfortunately, the VARI-METRIC models suffer from a series of limiting assumptions that are not satisfied in most technology-based large organizations. We identify these shortcomings and suggest a research agenda to deal with these issues. Important extensions include the study of capacitated systems, and the study of hybrid product structures, consisting of both repairable and consumable parts. When consumption and condemnation occur (i.e. not every broken part can be repaired), the operational availability of systems during their exploitation period becomes a function of the allocated resupply budgets. This highly important field, relating issues such as maintenance policies, spare parts repair and resupply, to concepts of life cycle management, seems unexplored so far.

Spare parts management for technical systems : resupply of spare parts under limited budgets

Abstract In this paper, we study the operational availability of a complex technical system consisting of several components. The components are subject to breakdowns, and hence for each component a limited number of spare parts are held in stock. If a systems component fails and it can not be replaced immediately, due to a lack of spares, the system becomes unavailable until a new component is installed. Failed components are disposed of and hence, to keep the spare parts stock at an appropriate level, new components have to be purchased. We assume that only a limited annual budget is available for procurement, while any further procurement requires a considerable lead time. We investigate at an aggregate level what budgets are needed to attain a target availability level for the system. In addition, we develop various operational strategies for spending the annual budget during each year. Numerical results indicate that the so-called Balance Focussed strategy provides the best results in terms of system availability as a function of time.

Exact and approximate analysis of multi-echelon, multi-indenture spare parts systems with commonality

General spare parts networks, in which items are both repaired and stocked for future use have received considerable attention since the pathbreaking work of Sherbrooke [20] in 1968. In this chapter, we present both an exact and, under somewhat relaxed assumptions, a fast approximate evaluation method of fairly general multi-echelon, multi-indenture spare parts networks that serve to support the operation of technologically highly involved field systems. These evaluation methods provide the basis for a procedure to optimize the availability of these systems, given limited spare parts budgets. In this introductory section, we first describe the general structure of the networks we wish to study, and we motivate their importance. Next, we discuss some key references and finally summarize the main contributions of the current chapter.

Capacitated two-echelon inventory models for repairable item systems

In this paper, we consider two-echelon maintenance systems with repair facilities both at a number of local service centers (called bases) and at a central location. Each repair facility may be considered to be a job shop and is modeled as a (limited capacity) open queuing network, while any transport from the central facility to the bases (and vice versa) is modeled as an ample server. At all bases as well as at the central repair facility, ready-for-use spare parts are kept in stock. Once an item in the field fails, it is returned to one of the bases and replaced by a ready-for-use item from the spare parts stock, if available. The returned failed item is either repaired at the base or shipped to and repaired at the central facility. In the case of local repair, the item is added to the local spare parts stock as a ready-for-use item after repair. If a repair at the central facility is needed, the base orders an item from the central spare parts stock to replenish its local stock, while the failed item is added to the central stock after repair. Orders are satisfied on a first-come-first-serve basis while any requirement that cannot be satisfied immediately either at the bases or at the central facility is backlogged.

A Tribute to John A. Buzacott

This volume is dedicated to honoring John Buzacott, since 2002 Professor Emeritus of Management Science at the Schulich Business School of York University, Canada. John is one of the pioneers in the field of production and operations management. His contributions to the development of a unified framework and a rigorous scientific foundation of the major approaches currently used in the design, planning and control of manufacturing and service systems have inspired scholars throughout the world. His innovative use of stochastic models to explain many phenomena occurring in manufacturing organizations characterizes him, not only as a great researcher but also as a great teacher. For his many achievements in the field, he received an honorary doctorate (Doctor Honoris Causa) from Eindhoven University of Technology, the Netherlands, on April 27, 2001, where I had the privilege to act as his honorary supervisor. This brief account on the life and work of John is based on my laudatio, presented at that occasion.