After reading this article you will learn about:- 1. Introduction to Maintenance 2. Types of Maintenance 3. Procedure.
Introduction to Maintenance:
Machines, buildings and other service facilities are subject to deterioration due to their use and exposure to environmental conditions. If this process of deterioration is not checked, it may render them unserviceable. It is, therefore, necessary to attend to them from time to time, to repair and recondition them so as to enhance their life economically.
Maintenance aspect is more important specially in the case of machines due to their non-uniform pattern of wear and tear which depends on large number of factors.
Every machine is thoroughly tested and inspected by the manufacturers before selling it, and by the purchaser before it is put to use. When it is used, it will be subjected to wear and tear hence proper attention should be given to protect the machine and its components from undue wear and thus protect them from failures.
A proper attention means lubrication, cleaning, timely inspection and systematic maintenance. Maintenance of a machine means efforts directed towards the up-keep and the repair of that machine.
A major part of the expenditure is generally on men, material and maintenance in an industry. Every machine will require repairs even if it is best designed, hence the repair must be done at such a time when it may have least disruptions, i.e. machine may be repaired when it is not being used or its use may be postponed without affecting the production of the whole concern.
Therefore, checking of the machine is generally done when it is not in operation, so that the defect, if any, can be immediately and easily rectified without causing extensive damage to the plant.
In this way, we say that maintenance is responsible for the smooth and efficient working of an industry and helps in improving the productivity. It also helps in keeping the machines in a state of maximum efficiency with economy.
Realising the high importance of maintenance of plants and equipment’s. National Productivity Council, undertook the survey of engineering industries, and found that due to failure of the plants, equipment and machineries, non-availability is 28 per cent. Looking to this high percentage of failures, it is essential that the engineering units should improve their maintenance system.
Maintenance can be defined as a combination of actions carried out to replace, repair, service or modify the components in a plant or equipment so that it will continue to operate at a specified “availability” for a specified period of time.
Maintenance management is concerned with the direction and organization of resources in order to control the availability and performance of plant to some specified level.
The maintenance management is therefore a restorative function to ensure availability and efficiency of the existing plant, equipment and buildings at an optimum level.
Plant and equipment maintenance plays an important role in production management because breakdown creates problems such as:
(a) Loss of productive time
(b) Re-scheduling of production
(c) Need for sub-contracting work
(d) Temporary work shortage, as during break down workers may not have work for them.
Types of Maintenance:
Generally maintenance can be done in the following two ways:
1. Breakdown maintenance.
2. Preventive maintenance.
In the first case of maintenance, repair can be done after the breakdown occurs while in the second case maintenance is done on the basis of prediction or on the basis of periodical checking.
1. Break Down Maintenance:
Breakdown maintenance is defined as a maintenance activity conducted on a machine which has ceased functioning owing to shear or crushing or buckling or elongation or swelling or any other form of failure of any critical component of the said machine in order to enable the same to function as before by resorting to necessary replacement(s) of the same and/ or more number of components by new ones or usable old ones and/ or re-conditioning of the same within the minimum time period considering scope of work, available facilities and skill.
Breakdown of a machine can occur due to the following two reasons:
(i) Due to unpredictable failure of components which cannot be prevented.
(ii) Due to gradual wear and tear of the parts, which can be eliminated to a large extent by regular inspections, known as preventive maintenance. From experience it can be decided that, when a part should be replaced, so that breakdown can be avoided.
In breakdown maintenance, defects are rectified only when the machine cannot perform its function any longer, and the production department is compelled to call on the maintenance engineer for repairs. After repairing the defect, the maintenance engineers do not attend the machine again until another failure occurs.
In this type of maintenance, repair shall have to be done on failure, thus it may disrupt the whole production, if it is performing an important work. This method is expensive also due to increase of depreciation cost, payment to idle operators, overtime to the maintenance staff for doing the emergency repairs.
2. Preventive Maintenance:
Preventive Maintenance is defined as a maintenance activity conducted on a machine as per laid down schedule or frequency by making necessary or need-based replacement and/or reconditioning of component(s) within the pre-fixed time period of the said work in order to reduce and avert breakdown(s).
Preventive maintenance is sometimes termed as “planned maintenance” or “scheduled maintenance” or “systematic plant maintenance” etc. It is an extremely important function for the reduction of maintenance cost and to keep the good operational condition of equipment and hence increases the reliability.
Preventive maintenance aims to locate the sources of trouble and to remove them before the breakdown occurs. Thus it is based on the idea “prevention is better than cure”. Scheduled maintenance is always economical than unscheduled maintenance, as we all know that, “a stitch in time saves nine.”
Best safeguard against costly breakdown is to inspect, lubricate and checkup the equipment as frequently as possible. To take full use of equipment and to maintain it in reliable condition, necessary measures should be taken to prevent overloading, dampness, negligence and misuse of machines.
Frequency of inspection should be decided on the basis of the importance of the machine wear and tear of the machine and its delicacy. This periodic inspection or checking helps to find out the reasons leading to breakdown and to rectify them, when they are in minor stages.
Thus the repair can be done when one wants to do it, i.e. when it has least effect on the production schedule. Further this repair requires lesser time as compared to that of breakdown repair and thus down time is reduced by doing preventive maintenance.
Objectives:
Preventive maintenance has following main objectives:
1. To obtain maximum availability of the plant by avoiding breakdown and by reducing the shutdown periods to a minimum.
2. To keep the machine in proper condition so as to maintain the quality of the product.
3. By minimising the wear and tear, preserve the value of the plant.
4. To ensure for the safety of the workers.
5. To keep the plant at the maximum production efficiency.
6. To achieve all the above objectives with most economical combination.
Procedure for Maintenance:
Maintenance should be done considering all the above mentioned factors. Daily maintenance is done by the operators themselves. Before starting the work of their shift, cleaning, oiling and greasing should be done by the operators. For this purpose manufacturers used to issue maintenance instructions for their machines, which should strictly be followed.
Preventive maintenance of the machine depends largely on the operators. Hence, as far as possible, one operator be allotted for each machine, and when the same machine is used in more than one shift, one operator for each machine for each shift be allotted.
This system has following advantages:
(i) An operator gets used to the sound and working of his machine and notices any change immediately, which helps in investigation and rectification of the defect then and there. If operators are changed frequently, immediate check-up and timely repair cannot be possible.
(ii) It is easy to pin-point operators with bad operating habits. To remove these habits training can be arranged or disciplinary actions can be taken as the case may be.
(iii) The machine will remain in good conditions.
Periodic maintenance is generally conducted by the maintenance crew, specially trained for this purpose. The period should be decided on the basis of past experience. Apart from this, operating instructions should carefully be followed by the operators.
In case any abnormal sound or behaviour is noticed in the machine, he should immediately brought this into the notice of maintenance crew, so that the defect can be rectified immediately. Care must be taken that it may not be left for the latter date.
Inspections and lubrication schedules should be strictly followed. Inspection schedule should include the inspection of tools, accessories and other equipments.