Combined optimization of age based replacement and continuous review spare provisioning

Abstract

Block replacement is a preventive maintenance policy where a large number of identical, low cost operating components are replaced group-wise after certain time intervals. To ensure availability of spare items when operating components are to be replaced after breakdown or block replacement interVal, there is always a tendency to overstock the components. Excess inventory of the components involves substantial capitaL In a maintenance organization, normally, maintenance and spare parts provisioning are treated as separate problems, with special attention to maintenance policy. Inventory .systems matching stochastic demand pattern could also be designed and therefore combined optimization of maintenance and inventory functions can be anticipated to prove more costeffective than considering these policies separately. This general problem forms the basis of the present research In the present research a manufacturing system has been considered to solve the general problem of optimizing joint maintenance and inventory policies. This system comprises of several work centers and the focus is on the stochastic failures, replacements and order lead times of a single type of statistically identical items, common to each of the work centers. The system is highly complex to be described by a mathematical modeL A simulation model has, therefore been developed for the system operating under block replacement maintenance policy. The system response in terms of total cost, system downtime and work in process inventory accumulation have been studied for continuous review inventory policy. Various cost and system parameters have found to bear direct and significant effect on the optimal values of the decision variables. The results obtained clearly show that the joint optimized policy produces better results than that from the combinations of separately or sequentially optimized policies.