Reliability characteristics of components and systems with tolerable repair times

This paper provides general equations for calculating the time-dependent unavailability, the failure intensity and the distribution of the time to the first undesired event for components with tolerable down times. In many systems undesired events occur later than the components fail, and only if repairs are not completed within a grace period. Explicit equations are presented for several repair and maintenance categories, with ageing and renewed failure and repair characteristics. General methods for time-dependent grace periods and considerations for systems analysis are included.