Not Enough Pressure
21. Speed too low.
See item 5.
22. Air leaks in suction piping.
See item 8.
23. Mechanical defects.
See items 15, 16, and 17.
24. Obstruction in liquid passages.
Dismantle pump and inspect passages of impeller and casing. Remove obstructions.
25. Air or gases in liquid (tested in laboratory)
May be possible to overrate pump to point where it will provide adequate pressure despite condition.
reducing pressure on liquid to pressure in the
Better to provide gas separation chamber on suction line near pump, and periodically exhaust
suction line. Watch for bubble formation.
accumulated gas. See item 14.
See item 20.
26. Too small impeller diameter. (probable
cause if none of the above.)
27. Incomplete priming.
28. Suction lift too high.
29. Air leaks in suction piping.
30. Air leaks in stuffing box.
3 1. Air or gases in liquid.
Pump Operates For Short Time, Then Stops
Free pump, piping, and valves of all air. If high points in suction line prevent this, they need correcting.
See item 3.
See item 8.
See item 9.
See item 25.
32. Head lower than rating; thereby pumping
too much liquid.
34. Mechanical defects.
35. Suction inlet not immersed enough.
36. Liquid heavier (in viscosity or specific
gravity) than allowed for.
37. Wrong direction of rotation.
38. Stuffing boxes too tight.
Machine impellers OD to size advised by factory.
See item 14.
See item 15, 16, and 17.
See item 18.
Use larger driver. Consult factory for recommended size. Test liquid for viscosity and specific gravity.
See item 6.
Release gland pressure. Tighten reasonably. If sealing liquid does not flow while pump operates, replace
packing. If packing is wearing too quickly, replace scored shaft sleeves and keep liquid seeping for
39. Casing distorted by excessive strains from
suction or discharge piping.
Check alignment. Examine pump for friction between impeller and casing. Replace damaged parts.
40. Shaft bent due to damage.
Check deflection of rotor by turning on bearing journals. Total indicator run-off should not exceed 0.002
on shaft and 0.004 inch on impeller wearing surface.
41. Mechanical failure of critical pump parts.
43. Speed may be too high.
Check bearing and impeller for damage. Any irregularity in any of these parts will cause a drag on shaft.
Realign pump and driver.
Check voltage on motor.
44. Electrical defects.
The voltage and frequency of the electric current may be lower than that for which motor was built; or
there may be defects in motor. The motor may not be ventilated properly due to a poor location.
45. Mechanical defects in turbine, engine, or
other type of drive exclusive of motor.
If trouble cannot be located, consult factory.