Types of maintenance

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  • Types of Maintenance Prepared By; Rathod Abhik (13MMF0001)
  • What is Maintenance? & Why Maintenance?
  • 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 activities
  • Reasons for Maintenance Maintenance serves to protect the owners real estate investment in a number of ways Physical Integrity To keep the assets in good working order so as to minimize disruptions and downtimes. Risk Management To keep the assets in a state of good repair for the owners health and safety. Aesthetic Preservation To keep the assets from deteriorating in appearance and becoming unsightly. Responsible Stewardship To ensure that the assets achieve their full potential service life.
  • Duty of Care To satisfy a legislated duty that is owed to owners, occupants and guest on the property. Duty to Mitigate To prevent unnecessary damage to assets that may result in their premature failure.
  • Types Of Maintenance Breakdown maintenance Preventive maintenance 1. Periodic maintenance ( Time based maintenance - TBM) 2. Predictive maintenance I. Condition Monitoring Corrective maintenance
  • Break Down Maintenance It means that people waits until equipment fails and repair it. Such a thing could be used when the equipment failure does not significantly affect the operation or production or generate any significant loss other than repair cost. Preventive maintenance It is a daily maintenance ( cleaning, inspection, oiling and re-tightening ), design to retain the healthy condition of equipment and prevent failure through the prevention of deterioration, periodic inspection or equipment condition diagnosis, to measure deterioration. 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.
  • Periodic maintenance Time based maintenance consists of periodically inspecting, servicing and cleaning equipment and replacing parts to prevent sudden failure and process problems Predictive maintenance This is a method in which the service life of important part is predicted based on inspection or diagnosis, in order to use the parts to the limit of their service life. Compared to periodic maintenance, predictive maintenance is condition based maintenance. It manages trend values, by measuring and analysing data about deterioration.
  • Condition Monitoring Condition monitoring is the process of determining the condition of machinery while in operation. 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 Successfully using this programme enables the repair of problem components prior to failure. Condition monitoring not only helps plant personnel reduce the possibility of catastrophic failure, but also allows them to order parts in advance, schedule manpower, and plan other repairs during the downtime.
  • Corrective maintenance It improves equipment and its components so that preventive maintenance can be carried out reliably. Equipment with design weakness must be redesigned to improve reliability or improving maintainability
  • Advantages And Disadvantages Break Down Maintenance Advantages Disadvantages Lower start up cost Unpredictability Limited personnel requirement Equipment not maximised Reduced maintenance costs Indirect costs Potentially increased margins
  • Preventive Maintenance Advantages Disadvantages Over all very cost effective Catastrophic failure still a risk Flexibility can allow for adjustment of schedule to accommodate other work Labour Intensive Increased equipment life Performance of maintenance based on schedule not required Saved energy cost resulting from equipment running from pick efficiency Risk of damage when conducting unneeded maintenance Reduced equipment or process failure Saving not readily visible without a base line Over all saving between 12% to 18%
  • Predictive Maintenance Advantages Disadvantages Increased component operational life/availability Increased investment of diagnostic equipment Allows for pre-emptive corrective action Increased staff training for analysing data Decreased part and labour cost Saving not readily visible without a baseline/history Improved safety and environment Energy savings Over all saving between 8% to 12% over preventive maintenance
  • Condition Monitoring Advantages Disadvantages Extend bearing service life Monitoring equipment costs Maximise machine productivity Operational costs (running the program) Minimise unscheduled downtime Skilled personnel needed Safely extend overhaul intervals Strong management commitment needed. Improve repair time A significant run-in time to collect machine histories and trends is usually needed. Increased machine life Improve product quality Reduce product cost Enhance product safety
  • Corrective Maintenance Advantages Disadvantages Lower short-term costs Increased long-term costs due to unplanned equipment downtime. Requires less staff since less work is being done Possible secondary equipment or process damage. Prone to neglect of assets
  • Case Study Aircraft Maintenance Aircraft maintenance is the overhaul, repair, inspection or modification of an aircraft and aircraft components Airlines authorities casually refer to the detailed inspections as "checks Different Types of checks 1. A check 2. B check 3. C check 4. D check Among all the checks A and B checks are lighter checks, while C and D are considered heavier checks.
  • A Check This is performed approximately every 500 - 800 flight hours or 200 - 400 cycles. It needs about 20 - 50 man-hours and is usually performed overnight at an airport gate or hangar. The actual occurrence of this check varies by aircraft type, the cycle count (take off and landing is considered an aircraft "cycle"), or the number of hours flown since the last check. B Check This is performed approximately every 46 months. It needs about 150 man-hours and is usually performed within 13 days at an airport hangar. A similar occurrence schedule applies to the B check as to the A check. B checks may be incorporated into successive A checks
  • C Check This is performed approximately every 2024 months or a specific amount of actual flight hours (FH) 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 Checksusually a hangar at a maintenance base. The time needed to complete such a check is generally 12 weeks and the effort involved can require up to 6000 man-hours D Check This is by far the most comprehensive and demanding check for an airplane. It is also known as a Heavy Maintenance Visit (HMV). This check occurs approximately every 5 years. It is a check that, more or less, takes the entire airplane apart for inspection and overhaul. Also, if required, the paint may need to be completely removed for further inspection on the fuselage metal skin. Such a check can usually demand up to 50,000 man-hours and it can generally take up to 2 months to complete, depending on the aircraft and the number of technicians involved. It also requires the most space of all maintenance checks, and as such must be performed at a suitable maintenance base. Given the elevated requirements of this check and the tremendous effort involved in it, it is also by far the most expensive maintenance check of all, with total costs for a single visit ending up well within the million-dollar range.
  • NDT In Aircraft Maintenance During aircraft maintenance 'NONDESTRUCTIVE TESTING' (NDT) is the most economical way of performing inspection and this is the only way of discovering defects. In order to maintain the aircraft defects free and ensure a high degree of quality & reliability and as a part of inspection programme, usually following NDT methods are applied; 1) Liquid penetrant 2) Magnetic particle 3) Eddy current 4) Ultrasonic 5) Radiography (x-ray/gamma ray) 6) Visual/Optical 7) Sonic/Resonance 8) Infrared Thermography.