TABLE OF CONTENTS In the Ordinary Periodic Replacement Policy (OPRP), or Policy III [1, pp. 96-97], a unit is replaced with a new one every T p accumulated hours of operation; i.e., periodically at times k T p(k = 1, 2, 3, ). If the unit fails before T p hours of operation, it is minimally repaired so that its instantaneous failure rate, ?( T), corresponding to its times-to-failure pdf, f( T), remains the same as it was prior to failure. This would be the case when only one or a few components, from among several hundred that comprise the equipment, fail and get repaired or replaced, as the case may be. This way any change in the repaired or replaced components failure rate or mean life will not alter perceptibly the overall failure rate or mean life of the equipment involved. The minimal repair time is assumed to be negligible and each failure is detected instantaneously.
The cost function per unit, per hour operating time, is given by
where
| C p = | cost of the planned preventive replacement, |
| C mr = | cost of minimal repair, |
and
| E[ N( T p)] = | expected number of failures followed by minimal repair actions in an interval T p. |
The expected number of failures in a T p interval, per unit, is determined from
where
| ?( T) = | instantaneous failure rate function,... |
