Comparison of group replacement policies under minimal repair

Three replacement policies for a group of identical units are compared. (1) Units are periodically replaced all together. Between the periodic group replacements, minimal repairs are performed at failures. (2) The group replacement interval is divided into repair and waiting intervals. Minimal repairs are performed at failures during the repair interval, but no repair is made in the waiting interval, and the unit remains failed until the group replacement time comes. (3) Each unit undergoes minimal repair at failure during the repair interval. Beyond the interval, no repair is made until a number of failures. The expected cost rate expressions under each policy are derived. It is shown that the third policy is better economically than the other two policies. Numerical examples are given to demonstrate the results.