Experiments on optimal maintenance operations with emphasis on end-of-contract constraints

Abstract

To minimize the unnecessary costs that arise when machines or other objects fail, perhaps needing to be replaced during less than ideal occasions through what is known as reactive maintenance, a more active maintenance policy through which objects are continuously maintained in a preventative manner based on life expectancy or from a cost-perspective, is preferred. Mathematical models can be advantageous to utilize when scheduling these maintenance occasion. No model has at this time been shown to be the best within the sub field of Operations Research known as Maintenance Scheduling. The purpose of this project is to, through the addition of constraints and simulation, analyse two of the more prevalent models within this field: The Opportunistic Replacement Problem(ORP) and The Preventative Maintenance Scheduling Problem with Interval Costs(PMSPIC). Results show that the set-up cost dt for large system in which costs are time independent, i.e, dt = d, carry little influence over the resulting optimal schedule if the quotient d ci , where ci is the replacement cost of a component, is small. The inverse is shown to be true for systems consisting of a small number of components. It can thus be inferred that greater focus should be put on product development to avoid unnecessarily high maintenance costs in systems with few components and in which set-up costs are comparatively high. A quantitative comparison of both models was, unfortunately, not possible to perform due to time constraints. The results presented for the PMSPIC thus take the form of a qualitative discussion of its theoretical properties and how it can be likened to the ORP.