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MAINTENANCE AND TROUBLESHOOTING OF CENTRIFUGAL PUMPS

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MAINTENANCE AND TROUBLESHOOTING OF CENTRIFUGAL PUMPS

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MAINTENANCE AND TROUBLESHOOTING OF CENTRIFUGAL PUMPS

  1. 1. MAINTENANCE AND TROUBLE-SHOOTING OF CENTRIFUGAL PUMPS NAMITHA M R 2015664502
  2. 2. MAINTENANCE OF CENTRIFUGAL PUMPS  Proper maintenance of a CF pump is important to ensure its trouble-free and long service  The maintenance operations of CF pump includes: 1. Routine Preventive Maintenance 2. Overhaul or Repair operations
  3. 3. 1. ROUTINE MAINTENANCE  Performance of the pump should be observed daily  Any abnormalities in operation should be taken care of promptly  The alignment of the pump unit should be checked occasionally  Bearings should be lubricated regularly
  4. 4.  Half-yearly Maintenance  Pumps installed on cavity wells need half yearly checking  Shaft packing is checked by observing the leakage from it  Leakage from the stuffing box is excessive or the packing is worn  entire packing in the box will have to be replaced
  5. 5. CONTD…  Overhauling of stuffing box All the old packing rings are removed and interior of stuffing box is cleaned thoroughly  Shaft and shaft sleeve surface are properly cleaned before inserting the packing rings
  6. 6. CONTD…  If shaft sleeve is badly worn or scored, it is replaced  Straightness of the shaft should be ensured  Radial clearance between the shaft and the stuffing box bore is measured  Packing ring shouldn’t be inserted in a spiral form
  7. 7. CONTD…  Packing rings are fitted carefully: o Open them radially until the ends are wide apart as 1/2 the shaft dia.  the ends are turned apart in an axial direction slide the rings over the shaft  each ring is pushed in to the stuffing box, inserting the joint first o The joints of succeeding packing rings should be staggered
  8. 8. CONTD…  Assemble the gland ring and tighten the nuts by hands or using a spanner  When the pump is in operation, the nuts are again adjusted to achieve the desired leakage from the stuffing box  If decrease in discharge is found, the pump is opened and cleaned
  9. 9. 2.OVERHAULING OF PUMPS  Most overhaul work of CF pumps is concerned with the rotating parts  Overhauled annually or once in 2 years  In many situations, the operating conditions don't permit annual shutdown periods for overhaul
  10. 10. CONTD…  Situations call for a shutdown of the pumping plant for trouble shooting, repair and possible overhaul:  Fall-off in pump performance  Excessive noise during pump operation  Excessive vibration of pump  Symptoms of corrosion or erosion trouble
  11. 11. a) Dismantling of CF pumps o Pump has to be dismantled for overhauling o Pump is first disconnected from the piping system o Steps involved in dismantling a belt driven pump: 1. Remove the inlet and outlet flanges 2. Remove the bearing cap by removing the bolts holding it 3. Remove the grease cup and bearing lock nut
  12. 12. CONTD… 4. Remove the pedestal and take out the ball bearing, using a bearing puller 5. Remove the belt shifter 6. Remove the nuts and bolts joining the casings and remove the casing slowly, taking care not to damage the impeller and casing rings 7. Remove the impeller nut
  13. 13. CONTD… 8. Dismantle the rotating unit and remove the impeller slowly by hammering back the shaft gently, using a wooden block 9. Remove the impeller from the rotating unit 10. Remove the pulleys using a pulley puller 11. Dismantle the stuffing box
  14. 14. b) Overhauling of impellers o The eye, vanes, shrouds, wearing rings, passages and hubs are checked o Corrosion, cavitation and erosion are accompanied by the wearing of the impeller vane surfaces o Corrosion is due to warp or holes in the thinned surfaces o Impeller have to be replaced, if cavitation is severe o Impeller have to be thoroughly cleaned before inspection
  15. 15. c) Balancing of impeller o Badly worn or corroded impeller needs rebalancement o Balancing of an impeller can be checked by pressing it on an arbor, the ends of which rest on 2 parallel and level knife-edges, by hand o If found unbalanced, the metal is removed from the heavy side
  16. 16. d) Repair of shaft o Shaft is checked for bending with a dial gauge, by turning the shaft between lathe centres o If shaft is badly bent, it should be returned to the manufacturer o Reconditioning of the shaft will require welding or metalling, followed by rough finishing cuts o Final finishing is done by filing
  17. 17. e) Replacing of wearing rings o Proper clearance of the wearing ring is important o Increase in clearance results in leakage which decreases efficiency o If wearing rings are worn out, they have to be replaced
  18. 18. f) Repair of shaft sleeves o Shaft sleeves often get worn out when packed too tightly o Reconditioned by welding or metalizing, followed by a rough finishing cut o If wear is excessive, shaft sleeves have to be replaced
  19. 19. g) Repair of Non-stationary Components o Repair is negligible o Bed plate is kept clean of grease and oil at regular intervals o Joints and piping are checked regularly for leakage o Foundations are kept clean o Cracks in foundations are repaired in time o Surface of casing is painted
  20. 20. h) Reassembling the parts of a CF pump o Steps involved are: 1. Mount the pulleys on the shaft 2. Mount the casing and stuffing box bushes on the shaft 3. Gently mount the impeller on the shaft 4. Insert the impeller key carefully 5. Adjust the impeller at its correct position and tighten the impeller unit
  21. 21. CONTD… 6. Insert the gasket and grease it properly 7. Mount the casing by tightening its nuts and bolts 8. Insert the belt shifter at its correct position 9. Insert the shaft sleeve and tighten it properly 10. Mount the pedestal and align it properly by inserting the desired packing (shims)
  22. 22. CONTD… 11. Mount the ball bearing, on hand press, and tighten the bearing locking nut. Do not hammer the ball bearing 12. Mount the bearing cap
  23. 23. 3. TROUBLE-SHOOTING IN CF PUMPS  Troubles are of 3 types: mechanical, hydraulic and driver related  Mechanical troubles: Breakage of coupling or shaft  Hydraulic troubles: Failure to deliver water, reduction in discharge and over loading of the prime mover
  24. 24. a) No liquid delivered o Lack of prime o Speed of electric motor or engine too low o Discharge head too high o Suction lift too high o Impeller plugged o Vapor lock in suction line
  25. 25. b) Not enough water delivered o Air leaks o Worn wearing rings o Damaged impeller o Defective foot valve o Worn gaskets o Impeller eye too small c) Pump losses prime after starting
  26. 26. d) Overloading of Motor / Engine o Low discharge head o Packing too tight o Bent shaft o Distorted casing o Pump speed too high e) Overheating of stuffing box f) Excessive vibrations g) Overheating of bearings h) Rapid wear of bearings
  27. 27. THANK U!!!

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