Xylem AC2008B Series HSC3 Base Mounted Centrifugal Pump - Manual (Page 14)

14
Not Enough Pressure
CAUSES CURES
21. Mechanical defects. See items 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 May be possible to overrate pump to point where it will provide
laboratory, reducing pressure on adequate pressure despite condition. Better to provide gas separation
liquid to pressure in suction line. chamber on suction line near pump, and periodically exhaust accumu-
Watch for bubble formation.) lated gas. See item 13.
24. Too small impeller diameter. See item 18.
(Probable cause if none above.)
Pump Operates For Short Time, Then Stops
25. Incomplete priming. Free pump, piping and valves of all air. If high points in suction line pre-
vent this, they need correcting. See page 19.
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 Machine impeller’s OD to size advised by factory.
pumping too much liquid.
30. Cavitation See item 13.
31. Mechanical defects. See items 14 and 15.
32. Suction inlet not immersed See item 16.
enough.
33. Liquid heavier (in either Use larger driver. Consult factory for recommended size. Test liquid for
viscosity or specific gravity) viscosity and specific gravity.
than allowed for.
34. Wrong direction of rotation. See item 6.
35. Casing distorted by excessive Check alignment. Examine pump for friction between impeller and
strains from suction or casing. Replace damaged parts.
discharge piping.
36. Shaft bent due to damage – Check deflection of rotor by turning on bearing journals. Total indicator
through shipment, operation, run-out should not exceed 0.002 on shaft and 0.004 inch on impeller
or overhaul. wearing surface.
37. Mechanical failure of critical Check bearings and impeller for damage. Any irregularity in these parts
pump parts. will cause a drag on shaft.
38. Misalignment. Realign pump and driver.
39. Speed may be too high Check voltage on motor.
(brake hp of pump varies as the
cube of the speed; therefore,
any increase in speed means
considerable increase in
power demand).
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, If trouble cannot be located, consult factory.
engine or other type of drive
exclusive of motor.