2. Question?
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?
5. Imagine
…….
…….
…….
…….
…….
Imagine having no maintenance system
6. Maintenance in Service Industry
Hospital
Transport companies
Banks
Gas station
Shopping malls / retail
Restaurants
Hotels and resorts
7. Maintenance in Manufacturing Companies
Refinery
Petrochemicals
Electronic
Automotive
Furniture
Ceramics
Food and beverages
8. Operators less able to do repairs themselves
Machine and product failure can have effect on company’s operation and profitability
Losses due to breakdown
9. Maintenance and reliability is important
Maintenance and product quality
Maintenance and productivity
Maintenance and safety
Maintenance and supply chain
Failure cause disruption, waste, accident, inconvenience and expensive
11. Failure
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
12. Maintenance History
1.In the period of pre-World War II, people thought of maintenance as an added cost to the plant which did not increase the value of finished product.
Therefore, the maintenance at that era was
restricted to fixing the unit when it breaks because
it was the cheapest alternative
14. Maintenance History
Fix the equipment when it breaks
-Term terotechnology introduced.
-Recognition of need to present equipment failures.
-Models for preventive maintenance developed.
-Increased awareness of:
-Environment
-Safety
-Quality
-Need for reliable equipment.
-Reduction in costs.
Pre-World War II
Post-World War II
1980 Onwards
Time
Development of Maintenance
Figure 2.2 Maintenance History
(Adapted From Shenoy, Bhadury 1998)
15. Purpose of Maintenance
Attempt to maximize performance of production equipment efficiently and regularly
Prevent breakdown or failures
Minimize production loss from failures
Increase reliability of the operating systems
17. What is Maintenance? Maintenance is defined as: 1.The work under taken in order to keep or restore a facility to an acceptable standard.
18. 2. The combination of activities by which a facility is kept in, or restored to a state in which it can perform its acceptable standard What is Maintenance?
19. All actions necessary for retaining an item, or restoring to it, a serviceable condition, include servicing, repair, modification, overhaul, inspection and condition verification
Increase availability of a system
Keep system’s equipment in working orderWhat is Maintenance?
20. Maintenance Definition
British Standard Glossary of terms (3811:1993) defined maintenance as:
the combination of all technical and administrative actions, including supervision actions, intended to retain an item in, or restore it to, a state in which it can perform a required function.
23. MaintenancePreventive M. “To Keep” Corrective M. “To Restore” A facility to an acceptable standard
What is Maintenance?
24. (1) Complete InformationPlannedPreventive M. 70 % (2) Incomplete informationPlannedCorrective M. 20% (3) Without informationUnplanned Corrective M. (or Emergency) 10%
What are the main Types of Maintenance?
According to maintenance information availability
25. Maintenance Works
Planned
≥ 70 %
Unplanned
≤ 30 %
Minor repairs
≤ 20 %
Breakdown
≤10 %
PM
≥ 50 %
overhaul
≥ 20 %
Typical Work (man-hour) distribution in engineering industries
26. Minor repairs≤ 10 %
Breakdown≤ 5 % PM≥ 70 % Overhaul≥ 15 % Maintenance WorksPlanned ≥ 85 %Unplanned ≤ 15 %
Typical work effort (man-hour) distribution in critical industries (such as gas, oil, steam , power equipment)
27. What are the main Policies of Maintenance?
1.Breakdown/corrective maintenance
2.Preventive maintenance
2.a. Time-based preventive maintenance
-Pure time (calendar) based
-Used (running) time based
2.b. Condition-based preventive maintenance
“ Predictive maintenance PdM”
3.Opportunity maintenance
4.Fault finding
5.Design modification
6.Overhaul or Capital maintenance
28. Principle Objectives in Maintenance
To achieve product quality and customer satisfaction through adjusted and serviced equipment
Maximize useful life of equipment
Keep equipment safe and prevent safety hazards
Minimize frequency and severity of interruptions
Maximising production or increasing facilities availability at the lowest cost and at the highest quality and safety standards
Reducing downtime
30. Maintenance Objectives
Must be consistent with the goals of production (cost, quality, delivery, safety)
Must be comprehensive and include specific responsibilities
31. Maintenance Objectives
PLANT
M
A
I
N
T
E
N
A
N
C
E
Reduce Breakdowns
Reduce Downtime
Improving Equipment Efficiency
Improving Inventory Control
Implementing Cost Reduction
Maximising Production
Optimising Resources Utilisation
Optimising Useful Life of Equipment
Minimising Energy Usage
Providing Budgetary Control
32. Problems in Maintenance
Lack of management attention to maintenance
Little participation by accounting in analyzing and reporting costs
Difficulties in applying quantitative analysis
Difficulties in obtaining time and cost estimates for maintenance works
Difficulties in measuring performance
33. Problems Exist Due To:
Failure to develop written objectives and policy
Inadequate budgetary control
Inadequate control procedures for work order, service requests etc.
Infrequent use of standards
To control maintenance work
Absence of cost reports to aid maintenance planning and control system
34. Maintenance Costs
Cost to replace or repair
Losses of output
Delayed shipment
Scrap and rework
35. Types of Maintenance
Maintenance may be classified into four categories:
(some authors prefer three categories-scheduled and preventive maintenances are merged)
CorrectiveMaintenance(CM)
Scheduled maintenance
Preventive Maintenance (PM)
Predictive Maintenance (PDM)(Condition-based)
36. Run to Failure Maintenance (RTF)
Itistheoldesttypeofmaintenance.
Therequiredrepair,replacement,orrestoreactionperformedonamachineorafacilityaftertheoccurrenceofafailureinordertobringthismachineorfacilitytoatleastitsminimum acceptablecondition.
37. Run to Failure Maintenance (RTF)
Itissubdividedintotwotypes:
–Emergencymaintenance:itiscarriedoutasfastaspossibleinordertobringafailedmachineorfacilitytoasafeandoperationallyefficientcondition.
–Breakdownmaintenance:itisperformedaftertheoccurrenceofanadvancedconsideredfailureforwhichadvancedprovisionhasbeenmadeintheformofrepairmethod,spares,materials, labourandequipment.
38. Run to Failure Maintenance (RTF)
Disadvantages:
1.Itsactivitiesareexpensiveintermsofbothdirectandindirectcost.
2.Usingthistypeofmaintenance,theoccurrenceofafailureinacomponentcancausefailuresinothercomponentsinthesameequipment,whichleadstolowproductionavailability.
3.Itsactivitiesareverydifficulttoplanandscheduleinadvance.
39. Run to Failure Maintenance (RTF)
Thistypeofmaintenanceisusefulinthefollowingsituations:
1.Thefailureofacomponentinasystemisunpredictable.
2.Thecostofperformingruntofailuremaintenanceactivitiesislowerthanperformingotheractivitiesofothertypesofmaintenance.
3.Theequipmentfailurepriorityistoolowinordertoincludetheactivitiesofpreventingitwithintheplannedmaintenancebudget.
40. 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
47. 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
48. 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.
57. Advantages of PM
Advantages:
–Improving equipment availability/reliability
–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
62. 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.
63. 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
65. Why PM is Preferred
1. The frequency of premature failures can be reduced through proper lubrication, adjustments and cleaning.
2. If failure can not be prevented periodic inspections can help reduce its severity.
68. Determining the Size of Repair Crews
Problem:
A factory has 200 machines and the maintenance engineer supervises the repair crews who repair malfunctioning machines. The maintenance policy is to repair the broken down machine and bring back in production within 2 hours on the average. If average breakdown rate is 3.5 machines/hour and each repair crew can repair 0.25 machine per hour on the average. How many repair crews are required ?
69. Solution
The formula for average repair rate () is
1
ts = ----------or = + 1/ ts
-
Where = repair rate
= arrival rate of malfunctioning machines
ts = average time arrivals in the system
Required average repair rate
= 3.5 + 1 / 2 = 4 machines / hour
No. of Crews = machines/hour a crew can repair
= 4 0.25 = 16 repair crews required
72. What are the main factors, which affect the selection of Maintenance Policy?
Manufacturing maintenance recommendation
System availability
Safety factors
Production process
Operating conditions
Information availability
Resource availability
Operating & maintenance cost
Down time cost rate
Failure and repair characteristics
73. Maintenance Policy
Productivity
Operate to failure (RTF)
30 – 50 %
Good PM Program
Good bonus & incentive system
60 –80 %
Good PM Program based on RCM
Good bonus & incentive system
More than 80 %
What is the effect of Maintenance Policy on the Equipment Productivity?
74.
75.
76. Maintenance Strategy Comparison
Maintenance Strategy
Advantages
Disadvantages
Resources/ Technology Required
Application Example
Breakdown
No prior work required
Disruption of production, injury or death
May need labor/parts at odd hours
Office copier
Preventive
Work can be scheduled
Labor cost, may replace healthy components
Need to obtain labor/parts for repairs
Plant relamping, Machine lubrication
Predictive
Impending failures can be detected & work scheduled
Labor costs, costs for detection equipment and services
Vibration, IR analysis equipment or purchased services
Vibration and oil analysis of a large gearbox
77. Maintenance Strategy Implementation
Breakdown
Preventive
Predictive
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Year
100%
80%
60%
40%
20%
0%
Percentage of Maintenance Time by Strategy
