maintenance

7/21/2019 Maintenance

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MAINTENA

NCE



Maintenance Definition Maintenance is a set of organised activities that are carried out in orderto keep an item in its best operational condition with minimum costacquired.

Activities of maintenance function could be either repair orreplacement activities, which are necessary for an item to reach itsacceptable productivity condition and these activities, should be carriedout with a minimum possible cost.



Maintenance History 1. In the period of pre-orld ar II, people thought of maintenanceas an added cost to the plant which did not increase the value of

finished product.

!herefore, the maintenance at that era was

restricted to fi"ing the unit when it breaks because

it was the cheapest alternative



Maintenance History #. $uring and after orld ar II at the time when the advances ofengineering and scientific technology developed, people developedother types of maintenance, which were much cheaper such as

preventive maintenance.

In addition, people in this era classified

maintenance as a function of the production system



Maintenance Objectives Ma"imising production or increasing facilities availability at thelowest cost and at the highest quality and safety standards.

%educing breakdowns and emergency shutdowns.

&ptimising resources utilisation.

%educing downtime.

Improving spares stock control



Breakdown maintenance Breakdown maintenance implies thatrepairs are made after the equipment isfailed and can not perform its normal

function anymore

Quite justied in small factories where:

◦ Down times are non-critical and repair costs are less thanother type of maintenance

◦ Financial justication for scheduling are not felt



Breakdown maintenance !his type of maintenance is subdivided into three types(-

Remedial maintenance, which is a set of activities that are

performed to eliminate the source of failure without interrupting thecontinuity of the production process.



Breakdown maintenance Deferred maintenance, which is a set of corrective maintenanceactivities that are not immediately initiated after the occurrence of afailure but are delayed in such a way that will not affect the

production process.

Shutdown corrective maintenance, which is a set of correctivemaintenance activities that are performed when the production lineis in total stoppage situation.



Breakdown maintenance !he way to perform corrective maintenance activities is by conductingfour important steps(

1. Fault detection.

2. Fault isolation.

3. Fault elimination.

4. Verification of fault elimination.

In the fault elimination step several actions could be taken such asad)usting, aligning, calibrating, reworking, removing, replacing orrenovation.



Disadvantages of

BreakdownMaintenanceBreakdown generally occurs inappropriate timesleading to poor and hurried maintenance

!cessi"e delay in production # reduces output

Faster plant deterioration$ncreases chances of accidents and less safetyfor %oth workers and machines

&ore spoilt materials

Direct loss of prot

'an not %e employed for equipments regulated%y statutory pro"isions e(g( cranes) lift andhoists etc



reventive Maintenance

!M" !he maintenance carried out at predetermined intervals or according to prescribed criteria and intended to reduce the probability of failure or thedegradation of the functioning and the effects limited.



Advantages of PM *d"antages:-

+(,educes %reak down and there%y downtime

(.ass odd-time repair and reduces o"ertime of crews/(0reater safety of workers1(.ower maintenance and repair costs2(.ess stand-%y equipments and spare

parts3(Better product quality and fewer reworksand scraps

4($ncreases plant life5($ncreases chances to get production

incenti"e %onus




!M" %esearchers subdivided preventive maintenance into different kindsaccording to the nature of its activities(

Routine maintenance which includes those maintenance activitiesthat are repetitive and periodic in nature such as lubrication,cleaning, and small ad)ustment.

Running maintenance which includes those maintenance activities

that are carried out while the machine or equipment is running andthey represent those activities that are performed before the actual preventive maintenance activities take place.




!M" Opportunity maintenance which is a set of maintenance activitiesthat are performed on a machine or a facility when an unplannedopportunity e"ists during the period of performing plannedmaintenance activities to other machines or facilities.

Window maintenance which is a set of activities that are carriedout when a machine or equipment is not required for a definite

period of time.

Shutdown preventive maintenance, which is a set of preventivemaintenance activities that are carried out when the production lineis in total stoppage situation.



redictive Maintenance

!DM" 'redictive maintenance is a set of activities that detectchanges in the physical condition of equipment *signs offailure+ in order to carry out the appropriate

maintenance work for ma"imising the service life ofequipment without increasing the risk of failure.

It is classified into two kinds according to the methods

of detecting the signs of failure(◦ Condition-based predictive maintenance◦ Statistical-based predictive maintenance




!DM" Condition-based predictive maintenance

depends on continuous or periodic conditionmonitoring equipment to detect the signs of

failure.

Statistical-based predictive maintenance depends on statistical data from the meticulous

recording of the stoppages of the in-plant itemsand components in order to develop models for

predicting failures.




!DM" !he drawback of predictive maintenance is that it depends

heavily on information and the correct interpretation of theinformation.

ome researchers classified predictive maintenance as a typeof preventive maintenance.

!he main difference between preventive maintenance and predictive maintenance is that predictive maintenance usesmonitoring the condition of machines or equipment todetermine the actual mean time to failure whereas preventivemaintenance depends on industrial average life statistics.



Scheduled

Maintenance 6cheduled maintenance is a stitch-in-timeprocedure and incorporates

◦ inspection

◦ lu%rication

◦ repair and o"erhaul of equipments

$f neglected can result in %reakdown

0enerally followed for:

◦ o"erhauling of machines◦ changing of hea"y equipment oils

◦ cleaning of water and other tanks etc

maintenance

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