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The objective of this article is to present a methodology based on reliability and maintainability (R & M) parameters for effective implementation of life cycle costing in design and procurement of repairable systems. For this purpose, a number of life cycle cost models developed over the years have been reviewed, the important life cycle stages for repairable systems are identified and a generalised model for life cycle cost analysis is first proposed. The mathematical equations have been formulated for the life cycle stages, such as acquisition, installation and commissioning, operation, maintenance and repair and disposal. The focus is mainly on modelling the maintenance and repair costs, which are the major elements of repairable system life cycle cost. To model maintenance and repair costs, the stochastic point process approach is employed. The lifetime of repairable system is modelled using a two parameter Weibull distribution. The expected number of failures are estimated based on the assumption that the number of replacements of the components in an interval (0, t) follow renewal process (RP) in the first case and minimal repair process in the second case. Based on the expected number of failures, the lifetime maintenance and repair costs are estimated for the RP and the minimal repair process. A methodology to decide whether a renewal approach or minimal repair approach should be planned for a particular component is also presented. The proposed technique is then illustrated through its application to a typical repairable system, namely an industrial pump and the results obtained are presented along with a review for future work. The proposed model is believed to be a simple way for system designers to estimate and compare the life cycle cost of their different design alternatives at system design stage using system R & M parameters.

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For a product to be commercially successful and increasingly competitive in this global market place, it is imperative that engineers must understand and design for each phase in the life cycle of a product. The life cycle cost (LCC) of any piece of equipment, such as a pump represents the total cost to procure, install, operate, maintain and dispose of that equipment. For sustainment dominated products or systems, the lifetime energy and/or maintenance costs dominate the life cycle cost as compared to its initial cost. The initial cost is only a fraction of the life cycle cost. Therefore, a due consideration to the life cycle cost issues at product design stage is quite essential. The LCC analysis is recommended only at the product design phase, as up to 80% of product LCC is committed at this phase. A better understanding of the cost components that make up the life cycle cost is expected to provide the product designers an opportunity to considerably reduce product LCC. In this paper, a methodology for LCC analysis based on reliability and maintainability principles has been applied to three different pumps and the results of analysis have been compared. For analysis purpose, two pumps have been selected from the literature and the data available therein is utilized. The third pump is selected from a well known pump manufacturer from India and the required data is obtained directly from the manufacturer. To model the maintenance and repair cost the concept of expected number of failures in a given time interval has been applied. The maintenance and repair cost is estimated for two different maintenance and repair strategies, the renewal/replacement upon failure strategy and minimal repair upon failure strategy and under the conditions of constant failure rate (exponential distribution) in first case and increasing failure rate (Weibull distribution) in the second case. The results obtained have been presented and compared at the end. The methodology presented in this paper is expected to help the pump designers to estimate and compare the life cycle cost of their different design alternatives.