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1. Introduction to Maintenance

2. Maintenance
• Action necessary for retaining an item/restoring it to a serviceable condition which
include servicing, repair, modification, inspection and condition verification.
• Combination of actions carried out to replace, repair, or modify the components,
items, items & units of a plant so that it will continue to operate at specified
availability over a specified time.
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3. QUESTIONS
• Why do we need maintenance?
• What are the costs of doing maintenance?
• What are the costs of not doing maintenance?
• What are the benefits of maintenance?
• How can maintenance increase profitability of company?
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4. Lathe Maintenance
Lathe maintenance involves maintenance of
• Drive belt
• cross slide & compound rest
• Adjusting tailstock clamp
After 8 hours of work,
▫ Cleanliness of slideway, slidewaylubrication
After 40 hours of work,
▫ Tightness of screws, inside cabinet dirtoil
After 1000 hours of work,
▫ Drive belt wear, refill oilreservoir
Maintenance
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5. • To increase availability of a system
• To maximize performance of production equipment efficiently and regularly
• To prevent failure/ breakdown
• To increase reliability of the system
• To minimize frequency & severity of interruptions
Maintenance Objective
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6. • Failure: inability to produce work in appropriate manner
• Equipment / machine failure on production floor
● worn out bearing, pump, pressure leaks, broken shaft, overheated machine etc.
• Equipment failure in office
● failure of power supply, air-conditioned system, computer network, photocopy machine
• Vehicle failure
● brake, transmission, engine, cooling system
Failure
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7. • Electronic
• Automotive
• Petrochemicals
• Refinery
• Furniture
• Ceramics
• Food and beverages
Maintenance in Manufacturing Industry
• Hospital
• Restaurants
• Transport companies
• Banks
• Hotels and resorts
• Shopping malls / retail
• Gas station
Maintenance in Service Industry
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8. Types of Maintenance
Maintenance may be classified into four categories:
(some authors prefer three categories- scheduled and preventive maintenances are
merged)
• Corrective or Breakdown maintenance
• Scheduled maintenance
• Preventive maintenance
• Predictive (Condition-based) maintenance
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9. Corrective or Breakdown Maintenance
• Corrective or Breakdown maintenance implies that repairs are made
after the equipment is failed and can not perform its normal function
anymore
• Quite justified in small factories where:
▫ Down times are non-critical and repair costs are less than other type of
maintenance
▫ Financial justification for scheduling are not felt
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10. Disadvantages of Corrective Maintenance
• Breakdown generally occurs inappropriate times leading to poor and hurried
maintenance
• Excessive delay in production & reduces output
• Faster plant deterioration
• Increases chances of accidents and less safety for both workers and machines
• More spoilt materials
• Direct loss of profit
• Can not be employed for equipments regulated by statutory provisions e.g.
cranes, lift and hoists etc.
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11. Scheduled Maintenance
• Scheduled maintenance is a stitch-in-time procedure and incorporates
▫ inspection
▫ lubrication
▫ repair and overhaul of equipments
• If neglected can result in breakdown
• Generally followed for:
▫ overhauling of machines
▫ changing of heavy equipment oils
▫ cleaning of water and other tanks etc.
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12. Preventive Maintenance (PM)
• Principle – “Prevention is better than cure”
• Procedure - Stitch-in-time
• It
▫ Locates weak spots of machinery and equipments
▫ Provides them periodic/scheduled inspections and
minor repairs to reduce the danger of unanticipated
breakdowns
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13. Candidates for Preventive Maintenance
Mean Time Between Failure (MTBF)
Frequency of Failure
Good candidates
have more normal
distribution with
low variability
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14. Advantages of PM
• Advantages:
▫Reduces break down and thereby down time
▫Lass odd-time repair and reduces over time of crews
▫Greater safety of workers
▫Lower maintenance and repair costs
▫Less stand-by equipments and spare parts
▫Better product quality and fewer reworks and scraps
▫Increases plant life
▫Increases chances to get production incentive bonus
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15. Predictive (Condition-based) Maintenance
• In predictive maintenance, machinery conditions are periodically
monitored and this enables the maintenance crews to take timely
actions, such as machine adjustment, repair or overhaul
• It makes use of human sense and other sensitive instruments, such as
▫audio gauge, vibration analyzer, amplitude meter, pressure, temperature and
resistance strain gauges etc.
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16. Predictive Maintenance (Contd.)
• Unusual sounds coming out of a rotating equipment predicts a trouble
• An excessively hot electric cable predicts a trouble
• Simple hand touch can point out many unusual equipment conditions
and thus predicts a trouble
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17. Maintenance Costs
Cost
Breakdown Cost
Maintenance
Commitment
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18. Maintenance Costs
Cost
PM Cost
Breakdown Cost
Maintenance
Commitment
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19. Maintenance Costs
Cost
PM Cost
Breakdown Cost
Maintenance
Commitment
Total Maintenance Cost
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20. Maintenance Costs
Maintenance
Commitment
Cost
Total Maintenance Cost
PM Cost
Breakdown Cost
Optimal
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21. • Maintenance Strategy is concerned with identifying the components of the plant
which might require maintenance, determining the most appropriate maintenance
procedure and then listing the procedures in the form of a schedule for the plant
Maintenance Strategy
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22. • Deal with replaceability and repair characteristics
• Maintainability diagrams are an aid to determining a maintenance strategy. The
diagram includes only those parts that might require maintenance during the life of
the unit
• Parts are usually classified as
▫ Complex replaceable items: replace &repair
● Ex: Gearbox
▫ Simple replaceable items: replace &discard
● Ex: Drive belt
Maintainability Diagrams
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23. • Maintenance actions are taken at regular intervals or after a fixed cumulative output,
fixed number of cycles of operation, etc.
• Actions: Item replacement, repair and major strip-down for inspection
• It is effective only when failure mechanism is age related (i.e. item failure
predictable) The implication of the above is that FTM is an appropriate procedure for
simple items (e.g. air filters) but is usually difficult to justify in the case of complex
items (e.g. electric motors) because of the high cost of maintenance
Fixed Time Maintenance (FTM)
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24. Condition based Maintenance (CBM)
• Appropriate when the approach to failure is readily detectable by a monitorable
parameter
• The monitored-parameter can provide information about a single component (e.g.
the wear of a brake pad) or provide information that can indicate a change in any
number of different components (e.g. vibration from a turbo-generator).
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25. • Three ways of condition monitoring:
(i) Simple inspection (Qualitative checks based on look, listen and feel, Usually
cheap and carried out as part of a routine )
(ii) Condition checking (Done routinely and measuring some parameter which is
not recorded but is only used for comparison with a
control limit, Such checking only has value where there
is extensive experience of identical systems)
(iii) Trend monitoring (Measurement and graphical plotting of a performance or
condition parameter in order to detect gradual departure
from a norm)
Condition based Maintenance (CBM)
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26. • Aims to eliminate the cause of maintenance rather than minimizing effect of failure
• For items of high maintenance cost arising from poor maintenance, poor design
Design out maintenance (DOM)
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27. In order to establish an effective maintenance strategy, a systematic approach is needed that
takes into consideration:
1.Understand the characteristics of plant operation.
▫ Construct a process flow diagram
▫ Understand the production policy
▫ Rank the units by criticality
▫ Identify the maintenance scheduling characteristics
▫ Identify the existing maintenance objective and strategy
2. Establish a maintenance plan for each unit
3. Establish a maintenance schedule for the plant
4. Establish the initial policy for spare parts and reconditioning
Systematic Approach to Establish
Maintenance Strategy
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28. Thanks To all