MAINTENANCE AND TROUBLESHOOTING OF CENTRIFUGAL PUMPS

1. MAINTENANCE AND
TROUBLE-SHOOTING OF
CENTRIFUGAL PUMPS
NAMITHA M R
2015664502

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. 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.  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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. THANK U!!!