Repairable Systems and Availability

Abstract

In Chapter six the concepts of Availability will be explained and discussed. The Availability is a concept that refers to reparable systems. For such systems the time of operation is not continuous, since their operating life cycles are described by a sequence of up and down states. Therefore the system operates until it fails, then it will be repaired and so it returns to its original functioning state. It will fail again after some random time of operation, get repaired again, and this process of both failure and repair will reiterate; hence the state of the system alternates between a operating state and a repair state. In this case, the important variables to be determined are the times to failure and the times to repair. Availability is defined as “the aptitude of the element to perform its required function in given conditions up to a given point in time or during a given time interval assuming that any eventual external resource is assured.” The availability of a machine can also be defined as the percentage of time, in respect to total time, in which the machine is required to function.