A modified age reduction PM model in a finite time span

For an age reduction preventive maintenance (PM) model over a finite time span (L), it is found from literature that a shorter interval between each PM (T) can result in a better expected total maintenance cost (TC). The optimal policy of the stated PM model (called the original PM model) is usually obtained by searching the optimal value of T over the specified range (T
_min
, T
_max
) for a given number of PM (N) by minimizing the total maintenance cost where T
_min
and T
_max
are defined as L/(N+1) and L/N, respectively. However, the original PM model does limit the possibility of finding a smaller TC since the value of T is constrained in the range of (T
_min
, T
_max
). In this paper, we consider the idea of releasing the constraint of the searching range of T and propose a new PM model with age reduction in a finite time period which can have a better optimal solution than the corresponding original PM model. The algorithm of finding the optimal solution for the new model is developed. Examples of the proposed new model are provided and are compared with the corresponding original PM model.