Assis, R. and Sobral, J. (2019), “Analysis of the economic viability of maintaining an expensive spare as repairable and non-repairable alternative (in Portuguese)”, 15º. Congressos Nacional de Manutenção, 21-22 November, Braga, Portugal

Frequently, companies face the dilemma of approving (or not) an acquisition, together with a piece of equipment, of a set of substitution components, or even, of complete sections (a gear motor, an electric motor, a motorized valve, a hydraulic pump, an electro valve, a sensor, etc.), proposed by the supplier. If the company offers a capable and sizable maintenance service, organized and documented, it will postpone to the eve of the preventive intervention (systematic or programmed) to order the necessary components from the supplier. However, often the components (or organs) will fail before the planned preventive intervention date, due to random or exogenous failure modes very often originating from operational errors, therefore, making it necessary to maintain one or more units in stock. Frequently, in the case of expensive substitutes, the alternative is concentrating on maintaining an only substitute component in stock, or not. The point of substitutes is vast. Reference [1] shows how to determine the optimum economic quantity of changeable components to keep in stock for different pieces of equipment, working on different reliability conditions and different daily and annual operational plans. Reference [2] analyses the question of “Will it be economically viable to maintain expensive substitutes in stock?”. This paper takes a step forward in helping to complete that question, returning to the same case, but this time taking into consideration the repairable substitute (changeable) e some additional variables. The case modelled in EXCEL is solved with the Monte Carlo simultation method, bearing in mind the stochastic nature of the moments of failure.

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