L & T 1996: Repairable System Reliability
and thus the reliability of hydraulic excavators working in the field, which
were essentially repairable systems, were modeled and estimated. The repair
mechanism of the excavator was to simply replace a failed component by a new
one. Thus the component failure rates were modeled using independent renewal
processes. A non-parametric Kaplan-Meier type analysis suggested
three-parameter Weibull distributions for the inter-arrival times of these
component renewal processes. The threshold parameters were
estimated using a Bayesian technique and were assumed to be known thereafter.
The scale and shape parameters were estimated using the method of Maximum
Likelihood. Then with the aid of the renewal equation these MLE's were
utilized to approximate the MLE's of the component and excavator failure
rates. Standard errors were derived using the delta method.