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Maintenance EngineeringANIRUDH GOYAL

608MP13MPAE-1

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INTRODUCTIONWhat is Maintenance?Maintenance is work that is carried out to preserve an asset (such as a roof or a heating boiler), in order to enable its continued use and function, above a minimum acceptable level of performance, over its design service life, without unforeseen renewal or major repair activitiesWhat is Maintenance Engineering?Maintenance Engineering is the discipline and profession of applying engineering concepts to the optimization of equipment, procedures, and departmental budgets to achieve better maintainability, reliability, and availability of equipment.Maintenance, and hence maintenance engineering, is increasing in importance due to rising amounts of equipment, systems, machineries and infrastructure. Since the Industrial Revolution, devices, equipment, machinery and structures have grown increasingly complex, requiring a host of personnel, vocations and related systems needed to maintain them.

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OBJECTIVEOF

MAINTENANCE

Maximise

HIGH

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HistoryIt was until 1950 that a group of Japanese engineers began a maintenance practice, was simply following the recommendations of equipment manufacturers about the care that should be taken into the operation and maintenance of machines and devices.This trend was called "Preventive Maintenance". As a result, plant managers were interested in having their supervisors, mechanics, electricians and other technicians, develop programs to lubricate and making key observations to prevent equipment damage.Although this helped reduce losses of time, the Preventive Maintenance was an expensive alternative. The reason: Many parts were replaced based on time of operation, while they could have lasted longer and consumed unnecessarily long hours of work.The times and needs changed in 1960 when the concept, "Productive Maintenance" came into picture. Highest responsibilities were assigned to people related to the maintenance and considerations were made about the reliability and the design of equipment and plant. It was a profound change and generated the term "Plant Engineering" instead of "Maintenance", the tasks included a higher level of knowledge of the reliability of each component of machines and facilities in general.

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Types Of Maintenance• Breakdown Maintenance (Or Corrective Maintenance) • Preventive Maintenance• Total Productive Maintenance• Predictive Maintenance• Periodic Maintenance• Condition Based Maintenance

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• BREAKDOWN MAINTENANCEMaintenance is carried out following detection of an anomaly and aimed at restoring normal operating conditions. This approach is based on the firm belief that the costs sustained for downtime and repair in case of fault are lower than the investment required for a maintenance program. This strategy may be cost-effective until catastrophic faults occur.

Such a thing could be used only when the equipment failure does not significantly affect the operation or production or generate any significant loss other than repair cost.

• PREVENTIVE MAINTENANCEMaintenance carried out at predetermined intervals or according to prescribed criteria, aimed at reducing the failure risk or performance degradation of the equipment. The maintenance cycles are planned according to the need to take the device out of service. The incidence of operating faults is reduced.It is further divided into periodic maintenance and predictive maintenance. Just like human life is extended by preventive medicine, the equipment service life can be prolonged by doing preventive maintenance.

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• TOTAL PRODUCTIVE MAINTENANCE

Total productive maintenance (TPM) is a maintenance philosophy that requires the total participation of the workforce. TPM incorporates the skills of all employees and focuses on improving the overall effectiveness of the facility by eliminating the waste of time and resources. Typically, total productive maintenance is a concept that is most easily applied to a manufacturing facility.

TPM emphasizes all aspects of production, as it seeks to incorporate maintenance into the everyday performance of a facility. To do this the maintenance performance is one factor that is considered when evaluating the performance of the facility. One of the most important measurements of total productive maintenance is overall equipment effectiveness (OEE). It is a measure of availability, performance efficiency and quality rate. As such, equipment stopping, equipment working at less than peak capacity, and equipment producing poor quality products are all penalized when the OEE is determined.

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• PERIODIC MAINTENANCESignificant activities carried out regularly (according to predetermined schedule) to maintain the condition or operational status of a building, equipment, machine, plant, or system. Also called time based maintenance.

• PREDICTIVE MAINTENANCE Maintenance carried out by integrating analysis, measurement and periodic test activities to standard preventive maintenance.The gathered information is viewed in the context of the environmental, operation and process condition of the equipment in the system. The aim is to perform the asset condition and risk assessment and define the appropriate maintenance program.All equipment displaying abnormal values is refurbished or replaced. In this way it is possible to extend the useful life and guarantee over time high levels of reliability, safety and efficiency of the plant.

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• CONDITION BASED MAINTENANCEMaintenance based on the equipment performance monitoring and the control of the corrective actions taken as a result.The real actual equipment condition is continuously assessed by the on-line detection of significant working device parameters and their automatic comparison with average values and performance. Maintenance is carried out when certain indicators give the signaling that the equipment is deteriorating and the failure probability is increasing. This strategy, in the long term, allows reducing drastically the costs associated with maintenance, thereby minimizing the occurrence of serious faults and optimizing the available economic resources management.

The key to a successful condition monitoring programme includes:  1. Knowing what to listen for 2. How to interpret it 3. When to put this knowledge to use

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ADVANTAGES & DISADVANTAGES

BREAKDOWN MAINTENANCE

Lower start up cost

Limited personnel requirement

Reduced maintenance costs 

Potentially increased margins 

Unpredictability 

Equipment not maximised 

Indirect costs 

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Preventive Maintenance

Lower start up cost

Limited personnel requirement

Reduced maintenance costs 

Potentially increased margins 

Catastrophic failure still a risk

Labour Intensive

Performance of maintenance based on schedule not

requiredRisk of damage when conducting unneeded

maintenance

Over all very cost effectiveFlexibility can allow for

adjustment of schedule to accommodate other workIncreased equipment life

Saved energy cost resulting from equipment running from pick

efficiencyReduced equipment or process

failureOver all saving between 12% to

18%

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Total Productive Maintenance

Lower start up cost

Limited personnel requirement

Reduced maintenance costs 

Potentially increased margins 

Breakdown lossesSetup and adjustment losses

Idling and minor stoppage losses

Speed losses

Strat-up/ yield losses

Quality defects and rework losses

Productivity ImprovementQuality Improvement

Cost ReductionEmployee Ownership

Improved working environmentIncreased Plant Reliability

Customer Satisfaction

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Predictive Maintenance

Lower start up cost

Limited personnel requirement

Reduced maintenance costs 

Potentially increased margins 

Increased investment of diagnostic equipment

Increased staff training for analysing data

Saving not readily visible without a baseline/history

Increased component operational life/availability

Allows for pre-emptive corrective action

Decreased part and labour costImproved safety and

environmentEnergy savings

Over all saving between 8% to 12% over preventive

maintenance

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Condition Based Maintenance

CBM is performed while the asset is working, this lowers disruptions to

normal operationsReduces the cost of asset failures

Improves equipment reliabilityMinimizes unscheduled downtime

due to catastrophic failureMinimizes time spent on

maintenanceMinimizes overtime costs by

scheduling the activities

Condition monitoring test equipment is expensive to install, and databases cost

money to analyzeCost to train staff – you need a

knowledgeable professional to analyze the data and perform the work

Fatigue or uniform wear failures are not easily detected with CBM measurementsCondition sensors may not survive in the

operating environmentMay require asset modifications to

retrofit the system with sensors

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CASE STUDYWhat maintenance plans are adopted by commercial aircraft operators and how are these being accomplished in a cost effective manner?

Modern industries focus mainly on implementing lean methodologies and Just – In - Tim e ( J I T ) systems by incorporating better reliability systems in their maintenance operations. Same situation exists in aviation industries too, where it is found that components that don’t require frequent maintenance or removals are subject to Preventive maintenance the components are subjected to maintenance/removal in a fixed time interval though it works well. Considering financial aspects of such maintenance, the industry has taken to Reliability Centered Maintenance (RCM) methodology.

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Aircraft Maintenance contributes more than 12% of the total operational cost in aircraft.

Reliability Centered Maintenance, or RCM, is a logical, structure framework for determining the optimum mix of applicable and effective maintenance activities needed to sustain the desired level of operational reliability of systems and equipment while ensuring their safe and economical operation and support.

RCM is a methodology to segregate the maintenance tasks based on their criticality and thereby revising its existing maintenance program considering financial benefits as well as ensuring safety.

Four step standard procedures:1. Record Part History Details (for failure data collection)2. Fault Isolation3. Reliability Analysis and 4. Reliability report showing revised maintenance program

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Aircraft Maintenance Checks

• Aircraft maintenance checks are periodic inspections that have to be done on all commercial/civil aircraft after a certain amount of time or usage.

• Airlines and airworthiness authorities casually refer to the detailed inspections as "checks", commonly one of the following:

A Check B Check C Check D Check

• A and B checks are lighter checks, while C and D are considered heavier checks.

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• CHECK ‘A’

This is performed approximately every 400-600 flight hours or 200–300 cycles (takeoff and landing is considered an aircraft "cycle"), depending on aircraft type.It needs about 150-180 man-hours and is usually on the ground in a hangar for a minimum of 10 hours. The actual occurrence of this check varies by aircraft type, the cycle count, or the number of hours flown since the last check. The occurrence can be delayed by the airline if certain predetermined conditions are met.

• CHECK ‘B’

This is performed approximately every 6-8 months. It needs about 160-180 man- hours, depending on the aircraft, and is usually completed within 1–3 days at an airport hangar.A similar occurrence schedule applies to the B check as to the A check. However, B checks may also be incorporated into successive A checks, i.e.: Checks A-1 through A-10 complete all the B check items.

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• CHECK ‘C’

This is performed approximately every 20– 24 months or a specific amount of actual flight hours (FH) or as defined by the manufacturer. This maintenance check is much more extensive than a B check, requiring a large majority of the aircraft's components to be inspected.This check puts the aircraft out of service and until it is completed, the aircraft must not leave the maintenance site. It also requires more space than A and B checks. It is, therefore, usually carried out in a hangar at a maintenance base. The time needed to complete such a check is generally 1–2 weeks and the effort involved can require up to 6,000 man- hours. The schedule of occurrence has many factors and components as has been described, and thus varies by aircraft category and type.

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CHECK ‘D’

Because of the nature and the cost of such a check, most airlines — especially those with a large fleet — have to plan D checks for their aircraft years in advance. Often, older aircraft being phased out of a particular airline's fleet are either stored or scrapped upon reaching their next D check, due to the high costs involved in comparison to the aircraft's value.

On average, a commercial aircraft undergoes three D checks before being retired. Many maintenance, repair and overhaul (MRO) shops claim that it is virtually impossible to perform a D check profitably at a shop located within the United States. As such, only a few of these shops offer D checks.

Given the time requirements of this check, many airlines use the opportunity in order to also make major cabin modifications on the aircraft, which would otherwise require an amount of time that would have to put the aircraft out of service without the need for an inspection. This may include new seats, entertainment systems, carpeting, etc.

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Tasks Performed by Maintenance Personnel

• The basics types of tasks that are performed by maintenance personnel are each applicable under a unique set of conditions.

• The task types include:

Inspections of an item to find and correct any potential failures; Rework/remanufacture/overhaul of an item at or before some specified time or age limit; Discard of an item (or parts of it) at or before some specified life limit; and Failure finding inspections of a hidden- function item to find and correct functional failures that

have already occurred but were not evident to the operating crew.

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Sample Checklists• PROPELLER CHECK• ENGINE CHECK• CABIN CHECK• FUSELAGE AND EMPENNAGE CHECK• WING CHECKS• LANDING GEAR CHECK• FUNCTIONAL CHECK FLIGHT

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REFERENCES• https://www.fiixsoftware.com/maintenance-strategies/total-productive-maintenance/• http://www.mantenimientopetroquimica.com/en/typesofmaintenance.html• http://www.slideshare.net/• https://en.wikipedia.org/wiki/Maintenance,_repair,_and_operations#Preventive_maintenance• http://www.leansingapore.com/total-productive-maintenance-tpm/• www.flyingmag.com/aircraft/ modificationsmaintenance/maintenance- you-can-do-it• www.mainsaver.com/pdf/ Reliability_Centered_Maintenance_White_Paper.pdf• www.eaa393.org/Presentations/ Short_RCMCondMonMxMangement.pdf• www.prnewswire.com/.../top-20- commercial-aircraft-maintenance-repair-- overhaul-m…• https://www.iata.org/about/sp/areas/ Documents/engineering-maintenance.pdf• https://en.wikipedia.org/wiki/

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Thank You!Have A Nice Day