Optimal maintenance policies for machines subject to deterioration and intermittent breakdowns

Optimal preventive maintenance policies, for a machine subject to deterioration with age and intermittent breakdowns and repairs, are derived using optimal control theory. The optimal policies are shown to be of bang-bang nature. The extension to the case, when there are a large number of identical machines and several repairmen in the system, is considered next. This model takes into account the waiting line formed at the repair facility and establishes a link between this problem and the classical ´repairmen problem´. An example is presented in detail illustrating, the procedure to obtain the optimal maintenance policy and the optimum number of repairmen for a system consisting of two machines. The results obtained here extend and unify several recent results for the problem.