
Analysis of Instantaneous Availability Fluctuation ◾ 247
the preventive maintenance cycle is 29. At this moment, from the mean availabil-
ity viewpoint, 29 can be considered as the optimal preventive maintenance cycle.
When the preventive maintenance cycle exceeds 50, it has almost no effect on the
system mean availability.
As seen in Figure 8.18, the system mean availability increases as the preven-
tive maintenance cycle N increases. When the preventive maintenance cycle is
large enough and, especially, when it exceeds the research time interval, it can be
interpreted as there being no preventive maintenance in the system. is system is
deg