From Maintenance Theory of Reliability


If a system consists of a block or group of units, their ages are not observed and only their failures are known, all units may be replaced periodically independently of their ages in use. The policy is called block replacement and is commonly used with complex electronic systems and many electrical parts. Such block replacement was studied and compared with other replacements in [1], [2]. Furthermore, the n-stage block replacement was proposed in [3], [4]. The adjustment costs, which are increasing with the age of a unit, were introduced in [5]. More general replacement policies were considered and summarized in [6] [7] [8] [9] [10]. The block replacement of a two-unit system with failure dependence was considered in [11]. The optimum problem of provisioning spare parts for block replacement was discussed in [12] as an example of railways. The question, "Which is better, age or block replacement?", was answered in [13].

This chapter summarizes the block replacement from the book [1] based mainly on our original work: In Sections 5.1 and 5.2, we consider two periodic replacement policies with planned time T in which failed units are always replaced at each failure and a failed unit remains failed until time T. We obtain the expected cost rates for each policy and analytically discuss optimum replacement times that minimize them [14]. In Section 5.3, we propose the combined model of block replacement and no replacement...

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Topics of Interest

Overview An operating unit is repaired or replaced when it fails. If a failed unit undergoes repair, it needs a repair time which may not be negligible. After the repair completion, a unit begins to...

Overview Until now, we have dealt primarily with the basic maintenance models and their combined models. This chapter introduces modified and extended maintenance models proposed mainly by the author...

8.6 Inspection for a Finite Interval Most units would be operating for a finite interval. Practically, the working time of units is finite in actual fields. Very few papers treated with replacements...

11.1 ORDINARY BLOCK REPLACEMENT POLICY-POLICY VII In the ordinary block replacement policy (OBRP), a unit is replaced at predetermined time intervals k T p ( k = 1, 2, 3, ), and at failure by a new...

14.4 PREVENTIVE MAINTENANCE POLICIES AND SPARES PROVISIONING 14.4.1 AGE REPLACEMENT POLICY - POLICY I A unit is replaced preventively once it has reached a specified age, T p and correctively...

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