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Basics in Maintenance
- 1. Today we aregoing to learn the basics of maintenance & the method for the accountability of losses & the method to over come those losses by appropriate maintenance activity. By, Raghuttam Jorapurkar
- 2. What is Maintenance? Maintenanceis defined as engineering actions which are necessary for retaining or restoring an equipment, machine or system to the specified condition to achieve its maximum useful life.
- 3. Types of Maintenance Thereare major three types of maintenance 1. Preventive Maintenance 2. Breakdown Maintenance 3. Corrective Maintenance
- 4. 1. Preventive Maintenance Itincludes two types of Maintenance 1.1 Periodic Maintenance (TBM : Time Based Maintenance) 1.2 Predictive Maintenance (CBM : Condition Based Maintenance)
- 5. 1.1 Periodic Maintenance(TBM) In this type of maintenance, spares / consumable replacement activity of the equipment or machine is carried out as per predefined time period. Disadvantage : Spare cost become high Note : TBM is only spare part replacement activity
- 6. 1.1 Periodic Maintenance(TBM) A Periodic time based maintenance plan is to be prepared for our company.
- 7. 1.2 Predictive Maintenance(CBM) It is the determination of the condition of in-service equipment in order to predict when maintenance should be performed This maintenance can be easily carried out by electronic equipment like bearing echo meter, multimeter, IR temperature meter etc. Advantage : Cost effective & utilization of spares can be achieved up to 99%
- 8. 1.2 Predictive Maintenance(CBM) A Periodic condition based maintenance plan is to be prepared for our company.
- 9. 1.2 Predictive Maintenance(CBM) While performing this type of maintenance, check sheet should be updated for further analysis. Machine / equipment history card is to be updated regularly for analysis & timely action.
- 10. 2. Breakdown Maintenance Thismaintenance is carried out on all items where the time of failure or wearing out are not yet captured in history of the machine or equipment. The maintenance activity conducted to bring back the machine / equipment in working order which has worn out or failed.
- 11. 3. Corrective Maintenance Toimprove reliability & maintainability, corrective maintenance is must It can be achieved by implementation of kaizens on : a. MTBF improvement b. MTTR reduction
- 12. Breakdown If downtime ismore than 10 minutes due to equipment problem, it is “breakdown”
- 13. Minor Stoppage If downtimeis less than or equal to 10 minutes due to equipment problem, it is “minor stoppage”
- 14. Mean Time ToRepair (MTTR) • It is a basic measure of the maintainability of repairable items. • It represents the average time required to repair the equipment Total Breakdown Time Total Breakdown Incidences M. T. T. R. =
- 15. Mean Time ToRepair (MTTR) • It can be measured in minutes, hours or days • It should be very low & ideally it should be zero • While calculations of MTTR, there is no consideration of minor stoppages
- 16. Mean Time ToRepair (MTTR) Question : Calculate MTTR for the month of May 2014 in which there were 2 breakdowns of 65 & 75 min
- 17. Mean Time ToRepair (MTTR) According to formula of Total Breakdown Time Total Breakdown Incidences MTTR = 65 min + 75 min 2 MTTR =
- 18. Mean Time ToRepair (MTTR) 140 min 2 MTTR = 70 min= 70/60 hours= 1.16 hours=
- 19. Mean Time BetweenFailure (MTBF) It is nothing but the average time between failures of the system/equipment Total Working Time – Total Breakdown Time Total Breakdown Incidences MTBF =
- 20. Mean Time BetweenFailure (MTBF) • It can be measured in minutes, hours or days • It should be very high & ideally it should be infinite • There is no consideration of minor stoppages
- 21. Mean Time BetweenFailure (MTBF) Question : Calculate MTBF for the month of May 2014 in which there were 2 breakdowns of 111 & 222 min (Given : No. of working days were 24)
- 22. Mean Time BetweenFailure (MTBF) Working time = Working Days X 24 hours Working time = 24 days X 24 hours = 576 hours
- 23. Mean Time BetweenFailure (MTBF) Breakdown time= 111 min + 222 min Breakdown time = 333 min = 333/60 hours = 5.55 hours
- 24. Mean Time BetweenFailure (MTBF) Now as per formula of MTBF Total Working Time – Total Breakdown Time Total Breakdown Incidences MTBF = 576 – 5.55 2 MTBF = 285.22 hoursMTBF =
- 25. Uptime It is ameasure of the time a machine has been up without any downtime It is measured in percentage Available Time – Breakdown Time Available Time Uptime = X 100
- 26. Uptime Suppose, available timeis 24 day & breakdown time is 4 hours, then uptime will be Available Time – Breakdown Time Available Time Uptime = X 100 (24 X24) – 4 (24 X 24) Uptime = X 100 Uptime = 93.31 %
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