10
Not enough liquid delivered
CAUSES
CURES
17. Foot valve too small or partially
obstructed
18. Suction inlet not immersed deep
enough
19. Wrong direction of rotation
20. Too small impeller diameter
(probable cause if none of the
above)
Area through ports of valve should be at least as large as area
of suction pipe, preferably 1½ times. If strainer is used, net
clear area should be 3 to 4 times area of suction pipe.
If inlet cannot be lowered, or if eddies through which air is
sucked persist when it is lowered, chain a board to suction
pipe. It will be drawn into eddies, smothering the vortex.
Compare rotation of motor with directional arrow on
pump casing. Wrong rotation will cause pump damage.
Check with factory to see if a larger impeller can be used;
otherwise, cut pipe losses or increase speed, or both, as
needed. Be careful not to seriously overload drive.
Troubleshooting
Not enough pressure
21. Speed too low
22. Air leaks in suction piping
23. Mechanical defects
24. Obstruction in liquid passages
25. Air or gases in liquid (Test in
laboratory, reducing pressure on
liquid to pressure in suction line.
Watch for bubble formation.)
26. Excessive impeller clearance
27. Too small impeller diameter
(probable cause if none of
the above.)
See item 5.
See item 8.
See items 15, 16, and 17.
Dismantle pump and inspect passages of impeller and
casing. Remove obstruction.
May be possible to overrate pump to the point where it will
provide adequate pressure despite condition. It is better to
provide gas separation chamber on suction line near pump,
and periodically exhaust accumulated gas. See item 14.
Adjust impeller clearance.
See item 20.
Pump operates for a short time, then stops
28. Incomplete priming
29. Suction lift too high
30. Air leaks in suction piping
31. Air leaks in stuffing box
32. Air or gases in liquid
Free pump, piping and valves of all air. If high points in
suction line prevent this, they need correcting.
See page 5.
See item 3.
See item 8.
See item 9.
See item 25.
Summary of Contents for CSR
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