ABSTRACT
Almost all machines or equipment whether electrical or mechanical or electronic, assumed to behave in the same manner. These machines are normally expected to have one of the three types of behaviours with reference to the failures that occur. These three behaviours are as follows: the rate of failures is decreasing; the rate of failures is constant; and the rate of failures is increasing. Amazingly, every machine is found to have all the three behaviours siginificantly and distinctly in certain period of its lifetime. Therefore, it has gained so much of significance in replacement analysis studies. The two types of replacement policies considered are: Individual Replacement; and Group Replacement. Under the group replacement policy a decision will be taken so as to replace all the mechanical items irrespective of the fact that the items have failed - not failed, provided if any item fails, before the optimal time it may be replaced individually.
