Equipment life time optimization with respect to operational expenses

The subject of investigations is the equipment operational model, where the operational expenses are represented by planned replacement expenses and losses due to failures. The two replacement strategies are considered: “planned replacement at the end of predetermined life time or after a failure” and “planned replacement at the end of predetermined life time”. In the second case only working capacity is restored after failure. The optimal lifetime value is shown to depend on the ratio of planned replacement expenses and losses due to failure. The rated conditions for the optimal equipment lifetime and for the gamma-percentile life are obtained providing the distribution of time to failure is determined by the Weibull law. The expediency of the equipment group replacement is discussed.