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7 Troubleshooting
Symptom
Not enough pressure
Pump operates for short time, then
stops
Pump takes too much power
46
Cause
Mechanical defects
Obstruction in liquid passages.
Air or gases in liquid. (Test in
laboratory, reducing pressure on
liquid to pressure in suction line.
Watch for bubble formation.)
Too small impeller diameter.
(Probable cause if none above.)
Incomplete priming.
Suction lift too high.
Air leaks in suction piping.
Air or gasses in liquid.
Head lower than rating; thereby
pumping too much liquid.
Cavitation
Mechanical defects
G&L Pumps Series A-C 8300 Base Mounted Centrifugal Pump INSTRUCTION MANUAL
Remedy
See "Defective impeller" and "Foot
valve too small or partially
obstructed".
Dismantle pump and inspect
passages of impeller and casing.
Remove obstruction.
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 "Cavitation; insufficient
NPSH".
Check with factory to see if a larger
impeller can be used; otherwise, cut
pipe losses or increase speed — or
both, if needed. Be careful not to
seriously overload drive.
Free pump, piping and valves of all
air. If high points in suction prevent
this, they need correcting.
If no obstruction at inlet, check for
pipe friction losses. Static lift may be
too great. Measure with mercury
column or vacuum gauge while
pump operates. If static lift is too
high, liquid to be pumped must be
raised or pump lowered.
If liquid pumped is water or other
non-explosive, and explosive gas or
dust is not present, test flanges for
leakage with flame or match, or by
plugging inlet and putting line under
pressure. A gauge will indicate a leak
with a drop of pressure.
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 "Cavitation; insufficient
NPSH".
Machine impeller's OD to size
advised by factory.
1. Increase positive suction head on
pump by lowering pump.
2. Sub-cool suction piping at inlet to
lower entering liquid
temperature.
3. Pressurization suction vessel.
See "Defective impeller" and "Foot
valve too small or partially
obstructed".
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