Inspection schemes for general systems

An inspection scheme is an integral part of any maintenance policy and we usually have to determine the time points at which the system should be inspected to make sure that the system availability requirement is met satisfactorily. There are many optimal policies for the determination of inspection times. This paper deals with periodic inspection with the emphasis on meeting the availability requirement. Five models for assigning the inspection times are studied. For these models, limiting average availability, long-run inspection rate, instantaneous availability and instantaneous inspection rate, are all derived. The relationships among the models are also discussed. A numerical example is presented to illustrate the differences for the cases of steady-state availability and instantaneous availability.