Department of Industrial Engineering, K. N. Toosi University of Technology
This paper studies a warm standby repairable system including two dissimilar units, one repairman and imperfect switching mechanism. Times to failure and times to repair of active and standby units are assumed to be exponentially distributed. Two cases of unreliable switching mechanism are considered. In case one, the failed active unit will be replaced by the available warm standby unit with coverage probability. However, in case two, the switching mechanism is repairable and its failure time and repair time are also exponentially distributed. Using Markov process and Laplace transforms, the explicit expressions of the mean time to failure, MTTF, and the steady state availability of the two systems are derived analytically. Finally, by solving a numerical example, comparison of the two systems are made based on various reliability and availability characteristics. Moreover, sensitivity analyses of the reliability and availability indexes with respect to the model parameters are accomplished.