TYPE OF MAINTENANCE
The maintenance can be classified as follows:
(1) Preventive maintenance.
(2) Break down maintenance.
PREVENTIVE MAINTENANCE
The objective of a preventive maintenance programme is to reduce the number of avoidable breakdowns. Breakdowns in the production line increase the cost of production and the production may be an unprof itable one. For want of little maintenance whole process may become idle. Preventive maintenance is expensive. It requires shop facilities, skilled labour, keeping records and stocking of replacement parts. The cost of down time (the time during which process remain idle) may be ten or more times the actual cost of repair. Hence it is very essential for a unit using mass production techniques to have a preventive mainte nance schedule.
Preventive maintenance programme should be prepared keeping in mind that too many inspections are a waste of money while insuffi cient inspection may result in break down in the system. The frequency of inspection should depend on the equipments contribution to profit able production, its duty cycle, age, overload and other pertinent fac tors.
The manufacturer should recommend an inspection cycle which may be modified later by experience. A good maintenance programme provides for scheduled stoppage of work for routine overhauls during the period of least usage rather than risk a breakdown during inoppor tune time. Thus preventive maintenance can be done according to the convenience of the factory.
When planning a preventive maintenance programme all equip ments should be classified according to its role in the manufacturing process. Machinery and control equipment that could stop production due to break down should be classified as vital equipment and should be provided with a balanced preventive maintenance programme. Other equipments by which the production is not likely to suffer much, should be classified as non-vital equipments such as fan, water cooler, air conditioner, etc. For such items simplified maintenance programme may be used.
To provide same degree of maintenance for vital and non-vital equip ments is a waste of time and money. The cost of preventive mainte nance programme should be added to the unit cost of production.
Preventive maintenance has two components:
1. Scheduled maintenance.
2. Shut down maintenance.
Scheduled Maintenance
When the maintenance is done in a planned manner on due date it is called scheduled maintenance. Normally the period of this mainte nance is given by the manufacturer. This period can be adjusted on the basis of past experience.
Shut Down Maintenance
It is also called overhaul. It is planed in advance in such a manner that the production does not suffer to a great extent. It is done either before or after the peak season of production.
Advantages of Preventive Maintenance
(i) The sudden interruption to the process is avoided due to failure of machines and equipments.
(ii) It is useful for doing systematic maintenance and assessing the requirement of minor or major maintenance.
(iii) The chances of break down are minimised.
(iv) The cost of maintenance is kept low.
(v) Since the condition of machinery is known, the flexibility in operation could be planned.
(vi) The wear and tear of machine and equipment is reduced.
(vii) Working conditions are improved.
(viii) The life of machinery and equipment is increased.
(ix) Less requirement of standby equipment.
(x) Safety to the workers is increased.
(xi) Requirement of parts and accessories could be decided for major repair/overhaul.
BREAKDOWN MAINTENANCE
When the equipment goes out of order then the maintenance is called repair or break down maintenance. It has to be carried out as when break down occurs. The breakdown maintenance could be further sub divided into two parts :-
(a) Emergency Maintenance (Repair) or Rapid Maintenance.
(b) Normal or Routine Maintenance.
Emergency Maintenance
Some experts prefer to call it trouble shooting. It is a temporary measure to keep the equipment running for a short period so that whole process of manufacture does not go out of gear. But it should be followed by shut down maintenance. This type of maintenance can be equated to a vehicle going out of order on a high way. Then emergency maintenance is done there and when it is driven back to city it is taken to a garage for repairs. This is also known as rapid maintenance.
This type of maintenance is not suitable of small industries. As this is additional expenditure or maintenance. The regular maintenance will have to be done. In the case of small industries time taken for emergency maintenance and normal maintenance will be almost same So for the same work double expenditure will be made. Therefore for small industries regular repair work should be carried out instead of emergency repair.
Normal or Routine Maintenance
This maintenance is same as done in case of scheduled maintenance for the equipment which has broken down. To effectively implement the maintenance Programme, Electrical Maintenance Department should be provided in the organisation depending upon the size of the organisation.
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