Browsing by Subject "Block Replacement"

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Open Access
Maintenance and marginal cost analysis of a two-unit cold standby system
(1997) Hamdaoui, Chokri
The Marginal Cost Analysis (MCA) of maintenance policies is a concept gaining interest in the recent years. This approach, due to Berg, has been categorized as an Economics Oriented Approach, as different from the classical probability centered approach. The MCA has been successfully applied to the Age Replacement and the Block Replacement policies, and was shown to be flexible enough to permit extensions and generalizations. In this thesis, we apply the MCA approach to a more complex model. We consider a two-unit cold standby system. Upon failure of the working unit in the time interval [0,T) the unit is replaced by the standby unit if available. If the standby unit is in repair, the system is down, and a downtime cost is incurred. The item inspected at time T is in one of two states: “good” , or “critical” . The good unit continues operation, whereas a unit in critical state is sent to repair. The switchover is immediate. We derive and compare the marginal cost function as well as the long-run cost per unit time function.
Open Access
Modified block replacement models in discrete and continuous time
(2000) Arun, Pelin
In this study, we present modified multi-component block replacement policies. Units (items) are replaced only at prescribed times j = 1,2,... A failed unit is changed with a good one with probability a. Replacement time is negligible. Three replacement policies for models that are not represented as renewal processes are provided under this setup. Some reliability characteristics are discussed. In the first model, total control is considered. All units are controlled at time jT, j = 1,2,.... In the second model, a partial (group) control is studied in which a sample of size n, (0 < n < A) is taken from all units to inspect. And the last model deals with cyclic control: units are divided into r parties. Part}' k is controlled at time jT , j — 1,2,... where j = k (modulus r), k = l,2 ,...,r — 1 and if k is equal to zero then party r is controlled. A comparison between the partial (group) control and cyclic control is provided. We also introduced cyclic partial control which combines the partial and cyclic control policies. The cyclic partial control and cyclic control is compared as well. Cost type of functionals are considered and optimal replacement interval T* is studied as well.