TTT Plotting and Maintenance Policies


Klefsjo, Bengt; Westberg, Ulf   (1996, Marcel Dekker, Inc. and ASQC)   Lulea University, Lulea, Sweden

Quality Engineering    Vol. 9    No. 2
QICID: 11957    December 1996    pp. 229-235
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Article Abstract

One well-known maintenance policy, useful for nonrepairable parts primarily, is the age replacement policy. In that policy, the part is replaced (or repaired to an as-good-as-new state) at failure or when the part has reached the age T, whichever occurs first. The aim is to find the optimal replacement age T which minimizes the long-run maintenance cost per unit time. This maintenance policy was discussed in some recent papers by Brick et al. (1989) and Dodson (1994), and different solutions to obtain estimates of the optimal replacement age were suggested. However, there is another useful technique to handle this problem, namely to use TTT plotting. By using TTT plotting, it is easy to get a nonparametric estimate of the optimal replacement age under the age replacement policy when you have failure data or test data. The plotting technique had also been generalized recently to include censored data.


Maintenance,Age replacement,Graphical methods,Total time on test (TTT),Optimization

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