Inspection Policies for Repairable Systems

The usual practice of monitoring a production process is to inspect the process at a uniform rate. For processes involving failure mechanism that obey a Markovian model, the practice of inspecting uniformly over time is, usually, optimum. For non-Markovian systems, however, this practice of inspection at a uniform rate is generally not optimum. It is believed that the frequency of inspections should be increased with time for increasing-failure-rate models. In this article we address this issue of an appropriate inspection policy for non-Markovian systems. Further, associated with a non-Markovian system is the usual practice of repairing the machine to bring it back to an ‘in-control’ state. We assume that, at a moderate cost, the system can be repaired and that the residual life on this system will depend upon its current age. The replacement costs are high and a decision to replace this machine is undertaken only when a repair at this stage is not expected to yield positive economic benefits. The object...