A System with Two Spare Units, Two Repair Facilities, and Two Types of Repairers

Assuming exponential lifetime and repair time distributions, we study the limiting availability A? as well per unit time-limiting profit ? of a one-unit system having two identical, cold standby spare units using semi-Markov processes. The failed is repaired either by an in-house repairer within patience T or external expert who works faster but charges more. When there are facilities, allow regular to begin continue beyond if busy. Two models arise accordingly repairs one all during each visit. We show that (1) adding second already backed raises ?; (2) thereafter, facility improves both criteria further. Finally, determine whether must maximize these fulfill maintenance management objectives better than previously studied models.