Troubleshooting
The Troubleshooting Guide below allows you to review and diagnose potential problems that may be encountered
with SAM Engineering’s range of centrifugal pumps. The guide outlines common pumping problems and failures
with probable causes and procedures for checking and correcting possible faults.
Between regular maintenance inspections, be alert for signs of motor or pump trouble. Correct any trouble
immediately to AVOID COSTLY REPAIR AND SHUTDOWN.
No liquid delivery
CAUSES CURES
1. Lack of prime Fill pump and suction pipe completely with liquid.
2. Loss of prime Check for leaks in suction pipe joints and fittings; vent casing to remove accumulated
3. Suction lift too high If no obstruction at inlet, check for pipe friction losses. However, static lift may be to
mercury column or vacuum gauge while pump operates. If static lift is too high, liquid
raised or pump lowered.
4. Discharge system head too high Check pipe friction losses. Larger discharge piping may correct condition. Check that
5. Speed too low Check whether motor is directly across-the-line and receiving full voltage. Alternative
low; motor may have an open phase.
6. Wrong direction of rotation Check motor rotation with directional arrow on pump casing. Wrong rotation will cau
7. Impeller completely plugged Dismantle pump or use piping hand hole to clean impeller.
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Not enough liquid delivered
CAUSES CURES
8. Air leaks in suction piping If liquid pumped is water or other non-explosive, and explosive gas or dust is not pres
leakage with flame or match. For such liquids as gasoline, suction line can be tested b
inlet and putting line under pressure. A gauge will indicate a leak with a drop of press
9. Air leaks in stuffing box Increase seal lubricant pressure to above atmosphere.
10. Speed too low See item 5.
11. Discharge system head too high See item 4.
12. Suction lift too high See item 3.
13. Impeller partially plugged See item 7.
14. Cavitation; insufficient NPSH a. Increase positive suction head on pump by lowering pump or increasing suction pip
(depending on installation) level.
b. Sub-cool suction piping at inlet to lower entering liquid temperature.
c. Pressurise suction vessel.
15. Defective impeller Inspect impeller. Replace if damaged or vane sections badly eroded.
16. Defective packing Replace packing and sleeves if badly worn.
17. Foot valve too small or partially Area through ports of valve should be at least as large as area of suction pipe- preferab
obstructed is used, net clear area should be3 to 4 times area of suction pipe.
18. Suction inlet not immersed deep enough If inlet cannot be lowered, or if eddies through which air is sucked persist when it is lo
suction pipe. It will be drawn into eddies, smothering the vortex.
19. Wrong direction of rotation Compare rotation of motor with directional arrow on pump casing. Wrong rotation wi
20. Impeller diameter too small (probable Check with factory to see if a larger impeller can be used; otherwise, cut pipe losses o
cause if none of above) as needed. But be careful not to seriously overload drive.
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Not enough pressure
CAUSES CURES
21. Speed too low See item 5.
22. Air leaks in suction piping See item 8.
23. Mechanical defects See item 15, 16, 17.
24. Obstruction in liquid passages Dismantle pump and inspect passages of impeller and casing. Remove obstruction.
25. Air or gases in liquid (Test in laboratory, May be possible to over rate pump to point where it will provide adequate pressure de
reducing pressure on liquid to pressure in provide gas separation chamber on suction line near pump, and periodically exhaust a
suction line. Watch for bubble formation.) 14.
26. Excessive impeller clearance Adjust impeller clearance.
27. Impeller diameter too small (Probable See item 20.
cause if none of above)
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Pump operates for short time, then stops
CAUSES CURES
28. Incomplete priming Free pump, piping and valves of all air. If high points in suction line prevent this, they
item 5.
29. Suction lift too high See item 3.
30. Air leaks in suction piping See item 8.
31. Air leaks in stuffing box See item 9.
32. Air or gases in liquid See item 25.
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Pump takes too much power
CAUSES CURES
33. Head lower than rating; thereby Machine impeller's OD to size advised by factory.
pumping too much liquid
34. Cavitation See item 14.
35. Mechanical defects See item 15, 16, 17.
36. Suction inlet not immersed enough See item 18.
37. Liquid heavier (in either viscosity or Use larger driver. Consult factory for recommended size. Test liquid for viscosity and
specific gravity) than allowed for
38. Wrong direction of rotation See item 6.
39. Stuffing box too tight (Packing) Release gland pressure. Tighten reasonably. If sealing liquid does not flow while pum
packing. If packing is wearing too quickly, replace scored shaft sleeves and keep liqu
40. Casing distorted by excessive strains Check alignment. Examine pump for friction between impeller and casing. Replace d
from suction or discharge piping pipe strain.
41. Shaft bent due to damage - through Dismantle pump and inspect shaft.
shipment, operation, or overhaul
42. Mechanical failure of critical pump parts Check bearings and impeller for damage. Any irregularity in these parts will cause a d
43. Misalignment Realign pump and driver.
44. Speed may be too high (brake hp of Check voltage on motor.
pump varies as the cube of the speed;
therefore, any increase in speed means
considerable increase in power demand)
45. Electrical defects The voltage and frequency of the electrical current may be lower than that for which m
may be defects in motor. The motor may not be ventilated properly due to a poor loca
46. Mechanical defects in turbine, engine, or If trouble cannot be located, consult factory.
other type of drive exclusive of motor
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