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Replacement Policy

Replacement Policy

Let the service life time of all item be T and

n= number of items in a system which need to be replaced wheneve any of these fails or reaches T.

F(t) = number of items surviving at T

F'(t) = 1 -f(t) number of items that have failed

O (t) = Total operating time

Cf = Cost of replacement after failure of item

CPM= Cost of preventive maintenance

Cost of replacement after failure of service time T = n×f’(t) ×Cf

also Cost of replacement for item replaced before failure = n[1-f’(T)]Cpm

=n+f’(T)c f + n[1-f’ (T) Cpm

Hence we can replace an item when the total replacement cost given above is minimum where

O (t) = f(t) dt