A Modified Block Replacement Policy Using Less Reliable Items

A modified block replacement policy is examined with the purpose of excluding the wastefulness caused by the property that almost new items might be sometimes replaced at planned replacement times under the ordinary block replacement policy. This modified policy can be stated as follows: 1) Operating items are replaced by new items at times kT (k = 1,2,...), 2) If operating items fail in [(k - 1)T, kT - v), they are replaced by new items, and in [kT - v, kT), they are replaced by less reliable items than new items. Numerical comparisons between the proposed policy and the ordinary block replacement policy are carried out for Weibull distribution.