Modeling of tolerable repair time without affecting system reliability

Ideally, it is assumed that a system fails as soon as one of its components connected in series has failed. However, in many real-world system configurations do not allow the system failure immediately when a fault or component failure occurs, rather its reliability falls down at a faster rate, and soon the system fails prematurely. If the fault is rectified or the failed item is repaired within a specified time limit, system reliability curve is restored to its normal decreasing trend. The time gap, between the failure of a component or occurrence of a fault and the repair of the component or rectification of a fault so that no system failure, is observed and it is very important that the system reliability decreases at its normal rate. This allowable time gap can serve a guiding tool to the maintenance policy and management decisions. This paper proposes a reliability and maintainability based approach for calculating the grace period, commonly known as the tolerable repair time of a system component. The proposed model has been demonstrated for a belt conveyor system, used for transportation of mineral in the mines. The allowable repair time of the idler of the belt conveyor system was calculated using the cumulative failure distribution function.