Extension of the second Barlow strategy to the case of three types of preventive maintenances

The paper is concerned with a strategy for maintenance of a system of elements of different reliability. Unlike the second Barlow strategy, three types of preventive repairs are envisaged, e.g. current, mean term, and capital. Expressions are found for the system idling coefficient and for probability of faultless operation between two capital repairs. Some optimization aspects of repair periodicities in terms of minimal idling coefficient are considered with and without constraints on probability of faultless operation.