349 – Quality, Reliability and Measurement System
A Repairable System With Two Spare Units and Two Repair Facilities Serviced by Two Types of Repairers
Vahid Andalib
University of Maryland Baltimore County
Jyotirmoy Sarkar
Indiana University-Purdue University Indianapolis
We study a one-unit repairable system with two identical, cold standby spare units in terms of limiting availability and limiting profit per unit time, using semi-Markov processes, when life- and repair time distributions are exponential. The failed unit undergoes repair either by an in-house repairer within a randomly chosen exponential patience time T, or else by a visiting expert repairer, who works faster but charges at a higher rate. Since there are two repair facilities, we allow the regular repairer to begin repair or to continue repair beyond T, if the expert is busy. Two models arise according as the expert repairs one or all failed units during each visit. We show that (1) adding a second spare unit to a one-unit system backed by only one spare unit increases both criteria; (2) thereafter adding a second repair facility improves both criteria further. Finally, we determine whether the expert must repair one or all failed units in order to maximize these criteria. This optimal strategy fulfills the maintenance management objectives better than those in previously studied models.