Xylem 9100 Series Base Mounted Centrifugal Fire Pumps AC8585 REV.C - Manual (Page 24)

24
CAUSES CURES
Not Enough Pressure
21. Mechanical defects. See item 14 and 15.
22. Obstruction in liquid passages. Dismantle pump and inspect passages of impeller and casing. Remove
obstruction.
23. Air or gases in liquid. (Test in
laboratory, reducing pressure
on liquid to pressure in suction
line. Watch for bubble
formation.)
May be possible to over rate pump to point where it will provide
adequate pressure despite condition. Better to provide gas separation
chamber on suction line near pump, and periodically exhaust
accumulated gas. See item 13.
24. Too small impeller diameter.
(Probable cause if none above.)
See item 18.
Pump Operates For Short Time, Then Stops
25. Incomplete priming. Free pump, piping and valves of all air. If high points in suction line
prevent this, they need correcting. See page 20.
26. Suction lift too high. See item 3.
27. Air leaks in suction piping. See item 8.
28. Air or gases in liquid. See item 23.
Pump Takes Too Much Power
29. Head lower than rating; thereby
pumping too much liquid.
Machine impeller’s OD to size advised by factory.
30. Cavitation See item 13.
31. Mechanical defects. See items 14 and 15.
32. Suction inlet not immersed
enough.
See item 16.
33. Liquid heavier (in either
viscosity or specific gravity)
than allowed for.
Use larger driver. Consult factory for recommended size. Test liquid for
viscosity and specific gravity.
34. Wrong direction of rotation. See item 6.
35. Casing distorted by excessive
strains from suction or
discharge piping.
Check alignment. Examine pump for friction between impeller and
casing. Replace damaged parts.
36. Shaft bent due to damage –
through shipment, operation, or
overhaul.
Check deflection of rotor by turning on bearing journals. Total indicator
run-out should not exceed 0.002 on shaft and 0.004 inch on impeller
wearing surface.
37. Mechanical failure of critical
pump parts.
Check bearings and impeller for damage. Any irregularity in these parts
will cause a drag on shaft.
38. Misalignment. Realign pump and driver.
39. Speed may be too high (brake
hp of pump varies as the cube
of the speed; therefore, any
increase in speed means
considerable increase in power
demand).
Check voltage on motor.
40. Electrical defects. The voltage and frequency of the electrical current may be lower than
that for which the motor was built; or there may be defects in motor.
The motor may not be ventilated properly due to a poor location.
41. Mechanical defects in turbine,
engine or other type of drive
exclusive of motor.
If trouble cannot be located, consult factory.