ABSTRACT
Once the equipment enters service a whole new set of information will come to light, and from this point on the maintenance program will evolve on the basis of data from actual operating experience. This process will continue throughout the service life of the equipment, so that at every stage maintenance decisions are based, not as an estimate of what reliability is likely to be, but on the specific reliability characteristics that can be determined at the time
Decisions relating to probabilistic maintenance problems, such as deciding when to perform preventive maintenance on equipment that is subject to breakdown, require information about when the equipment will reach a failed state. The engineer never knows exactly when the transition of the equipment from a good to a failed state will occur, but it is usually possible to obtain information about the probability of this transition occurring at any particular time. When optimal maintenance decisions are being determined, knowledge of statistics is required to deal with such probabilistic problems.
