Condition Based Maintenance

It was not a wrong belief that the maintenance carried out at irregular intervals would give more benefits than carrying out at regular intervals (like in preventive maintenance) owing to following major reasons:

• Though the time of preventive maintenance is reached as per schedule, it is not necessary to conduct the PM, when the machine is running without any problem as it does no much improvement than simply adding the cost of maintenance in some occasions and disturbing the productive hours in few other cases.
• Put a simple question to yourselves whether you carry out this PM according to the calendar time or time of utilization. When the machine is not utilized as specified in a given period, how far is it justified to conduct PM?
• While you are conducting the PM as per the schedule but not the need, and when you reassemble certain machine parts there is often a possibility of mismatching of the components, may be because of worn-out parts, change of models, spurious parts, lack of standardization, lack of skill and knowledge, etc. It obviously leads to the loss.
• Should the PM schedule be same for all the machines uniformly? Is it not different for different machines? Certainly, it should be different for different machines. The high cost machines, the machines which are very critical (though low cost) in the production chain, the machines whose spares are scarcely available may require more care.
• Do you care equally for the health of an infant, a child, a teenager, a middle aged and an old age person? The answer must be "NO". Similarly in the machines also do, the machine bought newly and an old machine should not be treated equally. And an industry will have the machines of different ages. Again simply age will not be the criterion to decide the PM schedule but the hours of run is another factor.
• Last but not least, are you taking the machine condition into account? The condition of machine plays a greater role as it sometimes depends directly on the age or/and hours utilized, but indirectly affected by environment, the usage, and the complexity of design and amusingly on the PM also.

Now, one must accept the need of conducting the PM at irregular intervals depending condition of the machine which includes all the factors pointed out above such as age, hours utilized, cost of machine, cost and availability of spares, its criticality in the production chain, etc. These factors are also not constant but are subjected to dynamic changes. Hence, in such a complex, complicated and dynamically changing situations, a more appropriate maintenance philosophy one can think of, is Condition Based Maintenance (CBM). The condition-based maintenance in simple words can be described as a preventive maintenance carried out at irregular intervals based on the actual condition of the machine.