There are certain variables in this replacement policy.
- T = service life of every equipment
- F’(t) = 1 -f(t) = number of failed equipment
- F(t) = number of equipment surviving at service life T
- (t) = total operating time
- n= number of machinery in a system requiring replacement whenever anyone breaks down or stops functioning or reaches its designated T.
- CPM= cost related to preventive maintenance
- Cf = replacement cost after equipment stops functioning
- n[1-f’(T)]Cpm = n+f’(T)c f + n[1-f’ (T) CPM = replacement cost for equipment which gets replaced before break down
- T = n×f’(t) ×Cf = replacement costwhen the machine stops functioning after its service time
When O (t) = f(t) dt and the above stated total replacement cost is minimal, at that time equipment can be ideally replaced.