Optimal number of spare and optimal interval between overhauls for equipment group

Any equipment during operation can fail or degrade with time. Therefore, it is necessary to act on them to make repair when failure eventually occurs or, to avoid failure occurrence and their consequences. The objective of preventive maintenance is to reduce the probability of failure in time period after maintenance has been applied. Concerning corrective maintenance, the objective is to reduce the severity of occurrence of breakdowns and to restore systems to normal operating conditions in short time interval. This paper seeks a model that allows determining a maintenance policy, which combines preventive and corrective maintenance in order to minimise maintenance costs. The proposed maintenance policy will allow to avoid or reduce the consequences of equipment breakdowns on production, through spare availability; and additionally, to decrease failure occurrence through regular equipment maintenance. In many cases, optimisation models are not applied due to lack of data. To enable the application of the proposed model, a computational application has been developed to calculate model unknown variables, and moreover it will allow to record data which will be used for further analysis and, to estimate equipment lifetime failure distribution.