Optimal maintenance level of equipment with multiple components

The purpose of the paper is to provide a method for selection of an optimum level of repair by replacement of an equipment based on its cost. In a ship where the engineer has a vast variety of equipment and systems to operate and maintain within limited time frames and availability of human resources, it is often difficult to disassemble a whole equipment to replace a faulty component. It is instead a lot easier to just replace the faulty equipment with whole new equipment. However, such a decision comes at an enormous capital cost. Therefore, the key question is, can we have a model to help us arrive at a decision on the correct level of carrying out repairs?

The paper uses a model based on cost and convolution of failure distributions of critical sub-components of an equipment. Necessary assumptions based on real life experience have been incorporated in the model.

The paper used an example of a particular type of motor driven sea water centrifugal pump which was commonly used in main engine sea water system, firefighting system, air conditioning system, etc. The pump had one of the highest failure rates in the ship (approximately one failure per 150 days) and the engineers found it cost and time effective to replace the entire pump on failure rather than carrying out replacement of the failed components. The model analyzed that the engineer’s hunch was not off the mark.

The implication of the work presented in the paper will be savings in maintenance cost and downtime due to optimal level of repairs on a multi-component equipment. The limitations of the work are assumption of independence of failures of components. This may not be true in all the cases. Further, opportunity based maintenance has also not been considered.

The originality of the paper lies in the presentation of a method for selection of an optimum level of maintenance for a multi-component equipment