Abstract
This paper studies the comparisons of individual and group replacement policies for a two-machine series system. Suppose that manufacturer's production system which consists of two machines in series. For two machines, when any machine fails within the operating time, minimal repair is performed for machines by the manufacturer. Due to the inevitable deterioration of the machine, the machine may fail more frequently as its age or usage increases. Therefore, an appropriate preventive replacement (PR) of the machine may be suitable for reducing the number of failures and maintains the operation of the machine normally. When a PR action is performed, it incurs a replacement cost and a downtime cost. Hence, when the replacement cost is high, it might be worthwhile replacing both machines at the same time (called group replacement policy; GRP) instead of replacing them separately (called individual replacement policy; IRP). Under these maintenance policies, the maintenance cost rate models of individual and group replacement for a series system is derived and further, optimal preventive replacement time is obtained such that the expected total cost rate is minimized. Finally, some numerical examples are given to illustrate the influences of individual and group replacement policies to the expected total cost rate.
Highlights
In the production process, it is an important item whether production system is normal operation
The objective of this paper is to find the optimal individual replacement time ( T1*, T2* ) and group replacement time Tg* such that the expected total cost rate
1) Under the expected life time u1≈u2, when β2>2, the expected total cost rate of group replacement is lower than individual replacement
Summary
It is an important item whether production system is normal operation. If a unit fails well before replacement time the unit is replaced at failure or at a fixed time Under those policies, the expected cost of each model is constructed and the optimal replacement policy is obtained. The optimal replacement time is obtained and numerical examples are given to illustrate the impacts of replacement policy for the cost models. For a product with an increasing failure rate function, structural properties of the optimal replacement policy are derived and obtained which minimizes the long-run expected cost rate. Within the pre-specified individual replacement time Ti, the expected total repair cost of the machines Mi is (Cmi+Cdm1+Cdm2)Hi(Ti), i=1, 2. The objective of this paper is to find the optimal individual replacement time ( T1* , T2* ) and group replacement time Tg* such that the expected total cost rate. The expected total replacement cost of the machine Mi is Cri+Cdr1+Cdr, i=1, 2
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