Ralph Wildeman

A Review of Multi-Component Maintenance Models with Economic Dependence

In this paper we review the literature on multi-component maintenance models with economic dependence. The emphasis is on papers that appeared after 1991, but there is an overlap with Section 2 of the most recent review paper by Cho and Parlar (1991). We distinguish between stationary models, where a long-term stable situation is assumed, and dynamic models, which can take information into account that becomes available only on the short term. Within the stationary models we choose a classification scheme that is primarily based on the various options of grouping maintenance activities: grouping either corrective or preventive maintenance, or combining preventive-maintenance actions with corrective actions. As such, this classification links up with the possibilities for grouped maintenance activities that exist in practice.

Dynamic influences in multi-component maintenance

Most maintenance-optimisation models assume an infinite planning horizon and suppose that the failure process is stationary. Hence, information which is not known beforehand and which becomes available in the short term only, must be ignored. We consider in this paper a multi-component system with economically dependent components, and we compare the costs of a stationary-planning method with the costs according to an approach which can adapt this long-term plan to dynamically changing information (such as a variable use of components and the occurrence of maintenance opportunities). With numerical experiments we show that incorporating short-term information can yield considerable cost savings.

How to Determine Maintenance Frequencies for Multi-Component Systems? A General Approach

A maintenance activity carried out on a technical system often involves a system-dependent set-up cost that is the same for all maintenance activities carried out on that system. Grouping activities thus saves costs since execution of a group of activities requires only one set-up. By now, there are several multi-component maintenance models available in the literature, but most of them suffer from intractability when the number of components grows, unless a special structure is assumed. An approach that can handle many components was introduced in the literature by Goyal et al. However, this approach requires a specific deterioration structure for components. Moreover, the authors present an algorithm that is not optimal and there is no information of how good the obtained solutions are. In this paper, we present an approach that solves the model of Goyal et al. to optimality. Furthermore, we extend the approach to deal with more general maintenance models like minimal repair and inspection that can be solved to optimality as well. Even block replacement can be incorporated, in which case our approach is a good heuristic.

Determining economic maintenance frequency of a transport fleet

Goyal and Gunasekaran (1992) presented a model and an algorithm to determine the economic maintenance frequency of a transport fleet. The authors suggest that the algorithm is optimal, but is is not; it is often stuck in a local optimal solution. Even the example provided by the authors is not solved to optimality. We explain why the algorithm is not optimal and give the optimal solution of the example obtained by global optimization.

A GENERAL APPROACH FOR THE COORDINATION OF MAINTENANCE FREQUENCIES IN CASES WITH A SINGLE SET-UP

A maintenance activity carried out on a technical system often involves a system-dependent set-up cost that is the same for all maintenance activities carried out on that system. Grouping activities thus saves costs since execution of a group of activities requires only one set-up. By now, there are already several multi-component maintenance models available in the literature, but most of them suffer from intractability when the number of components grows, unless a special structure is assumed. An approach that can handle many components was introduced in the literature by Goyal et al. However, this approach requires a specific deterioration structure for components. Moreover, the authors present an algorithm that is not optimal and there is no information of how good the obtained solutions are. In this paper we present an approach that solves the model of Goyal et al. to optimality. Furthermore, we extend the approach to deal with more general maintenance models like minimal repair and inspection that can be solved to optimality as well. Even block replacement can be incorporated, in which case our approach is a good heuristic.

Joint Preventive Replacement in an Operational Planning Phase

In this paper we address the problem of combining preventive replacements in a multi-component maintenance system in an operational planning phase. Given an infinite or a finite time horizon, decisions concerning replacement of components have to be made at discrete time epochs within this horizon. We present a heuristic procedure that specifies an action for a given epoch, based on the current state of the system and on an expected behaviour of the system in the near future.