Maintenance Modules

GROUP MEMBERS

AMARASENA R.G.C. : 061004D

DAYANI . J : 061011V

NUWAN .U.P.A : 061040H

PAHATHKUMBURE. K.M.D.K.B : 061042P

THAASAN S. : 061053B

WICKRAMARATHNE T. I. :061060T

What is Maintenance?

The maintenance department is one of the greatest levers of profitability that any capital intensive organization has.

An average of 40 – 50% of a capital intensive industries operating budget is consumed by maintenance expenditure.

With the advances today in technology affecting maintenance this figure can be greatly reduced. As such maintenance is often an organizations largest single controllable expense.

Maintenance

Maintenance Types

Planned Unplanned

Unplanned maintenance

• Reparation will be conducted after the equipment fails

• Used when the equipment failure does not considerably affect the operations or generate any notable loss other than the repair cost

Unplanned Maintenance cont…

Advantages• Low maintenance cost• Low maintenance staffDisadvantages• High down time• Lower operational efficiency• Low quality outputs• Impaired health & safety

conditions

Planned Maintenance

Planned maintenance is organized and executed with planning and control by utilizing the application of recorded data.

It encompasses condition based maintenance, which is planned and progressed information received about a system or company structure's condition.

This information is gleaned from routine or continuous monitoring processes and preventative maintenance.

Advantages of planned maintenance

Releases front-line foremen from major planning duties and allows them more

time to supervise their crews. Provides procedures to plan, execute,

monitor and control maintenance resources.

Reduces delays in waiting for men, material, tools after a job is in progress.

Provides for systematic collection of materials prior to planned jobs.

Provides procedures to implement and continue a PM program

Planned Maintenance types

• Preventive Maintenance• Corrective Maintenance

Preventive Maintenance

Preventative maintenance is carried out at predetermined intervals or according to prescribed criteria, with the intention of reducing the probability of failure or the performance degradation of a system.

PM includes painting, lubrication, cleaning, adjusting, and minor component replacement to extend the life of equipment and facilities.

Purpose is to minimize breakdowns and excessive depreciation. Neither equipment nor facilities should be allowed to go to the breaking point.

To minimize the risk, has to be carefully planned and carried out by well-trained and motivated workers.

Advantages of preventive maintenance

Improved system reliability.Decreased cost of replacement.Decreased system downtime.Better spares inventory

management.

Corrective maintenance Maintenance actions

carried out to restore a item that can be failed in to a specified condition

Improve equipments enabling the preventive maintenance to be carried out easily

Equipment with design weakness will be redesigned

Advantages of Corrective Maintenance

Enhanced component life time Enable prior corrective actions Lower equipment downtime Quality improvement of the

products Enhanced the safety Strengthened worker moral Save energy

Disadvantages of Corrective Maintenance

Higher investment in diagnostic equipment

Higher investment for training

Corrective Maintenance Types

• Maintenance actions based on actual conditions

• Reparation of a machine which gives an unusual sound can be identified as an example

• Can identify and rectify problems at an early stage and can improve machinery reliability

Condition Based Maintenance(Predictive Maintenance)

Opportunistic Maintenance

Reparation of the components which are found to be defective or needs replacement in the immediate future

The components will be identified during the maintenance of a sub-system or a module

Opportunistic Maintenance cont…

As an example, identifying and rectifying a defective feeder, during the maintenance actions carried out for a faulty stitch cam in a knitting machine

Routine Maintenance• Includes activities which

are perform in planned basis to maintain and protect the conditions of equipments /processes

• Most simplest type of planned maintenance

• Oiling knitting machines in can be identified as an example

Design Out Maintenance• Design modifications to stop

the failure from occurring • Usually conducted based on

the past experiences• As an example; a design

modifications conducted to a yarn feeding finger in a knitting machine to avoid having plating effect. The identification the fault and designing the finger will be conducted based on the past experience

Other Maintenance Types

Reactive Maintenance• No measures are taken to

maintain the equipment because the designer should ensure that the design will reach it’s life time

Reactive Maintenance cont…

Advantages• Lower cost• Less staffDisadvantages• Increased unplanned downtime cost• Repair / replacement of equipment cost• Other equipment or process damage

due to the equipment failure

Maintenance Prevention Indicates a design

of a new equipment Drawbacks of

existing machines are studied before designing the new equipment

Maintenance Prevention cont…

• Rieter, developed modern rotor machines with innovative bearing and lubrication techniques

• This reduce the maintenance requirements in the modern machines than in the conventional rotor machines

Maintenance Prevention cont…

Advantages• Lower maintenance cost• Lower machine downtimeDisadvantagesHigher investment for trainingHigher investment for equipments

and technology

Maintenance ModelsMaintenance Models

ReplacementReplacementWhy?Why?

Company

Employee

Target

AchievementEmployee

&Machines

Replacement

Employees Machines

Immediate replacement after failing With continuous failureWith expectation of failure

Age Replacement Model

Time

Age

of M

achi

ne

T TTT

For the equipments of which cost of repair is higher if it fails while operating Cost of maintenance involves

Down time loss Cost due to low efficiency Replacement cost Down time cost

Assumptions of the ModelAssumptions of the Model

Cost of maintaining the equipment increases as the

equipment ages

The equipment used is operating continuously or

intermittently

Down time for repair and maintenance is ignored

The planning horizon is infinite

Every new piece of equipment has identical characteristics

Calculating the ‘T’ value Calculating the ‘T’ value

Total cost = Replacement cost + Maintenance cost – salvage value

G(t) = K + C(t) – S(t)

Time

Cost

Breakdown Cost

Maintenance Cost

Total Cost

Salvage Value

T

Min

imum

tota

l co

st

Advantages and Disadvantages of Advantages and Disadvantages of the Age Replacement Modelthe Age Replacement Model

Advantages• Simple and basic calculation• Once calculation is done it can be used for long time until

the characteristics of the product is changed

Disadvantages• Not suitable for the products of which characteristics are

changed time to time• This model does not consider about the unplanned

breakdowns of machines

Applications of the model in Applications of the model in Textile and Clothing IndustryTextile and Clothing Industry

For the vehicles used in both industries

For the changing time of auto cutter unless knife

is broken

Replacement of sewing machines

Planned replacement on Planned replacement on uncertaintyuncertainty

Replacing before it fails

Is it worthwhile doing a Is it worthwhile doing a planned replacement?planned replacement?

How likely it will happen?

How do we quantify it?

Probability

Impact

Planned replacement without a review

Consequences might be not worthwhile

No advantage in avoiding the failure

Throw out unused life away

Get nothing

Planned replacement should reduce the chances of a failure

Replaced part or person should perform better than the previous or be more reliable

For this :

Reliability

Failure

Replaced item Old item

Planned replacementPlanned replacement

Individual replacement

Group replacement

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Thank You !