Goulds Pumps 3408A - IOM - Manual (Page 31)

PREVENTIVE MAINTENANCE
TROUBLESHOOTING
Between regular maintenance inspections, be alert for signs of motor or pump trouble. Common symptoms are listed below.
Correct any trouble immediately and avoid costly repair and shutdown.
CAUSES CURES
No Liquid Delivered
1. Lack of prime Fill pump and suction pipe completely with liquid.
2. Loss of prime
Check for leaks in suction pipe joints and fittings; vent casing to remove
accumulated air.
3. Suction lift too high
If no obstruction at inlet, check for pipe friction losses. However, 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.
4. Discharge head too high
Check pipe friction losses. Large piping may correct condition. Check
that valves are wide open.
5. Speed too low
Check whether motor is directly across-the-line and receiving full voltage.
Or frequency may be too low; motor may have an open phase.
6. Wrong direction of rotation Check motor rotation with directional arrow on pump casing.
7. Impeller completely plugged Dismantle pump and clean impeller. Not Enough Liquid Delivered
Not Enough Liquid Delivered
8. Air leaks in suction piping
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.
9. Speed too low See item 5.
10. Discharge head too high See item 4.
11. Suction lift too high See item 3.
12. Impeller partially plugged See item 7.
13. Cavitation; insufficient NPSH (depending
on installation)
a. Increase positive suction head on pump by lowering pump.b. Sub-cool
suction piping at inlet to lower entering liquid temperature.c.
Pressurization suction vessel.
14. Defective impeller
Inspect impeller, bearings and shaft. Replace if damaged or vane sections
badly eroded.
15. Foot valve too small or partially obstructed
Area through ports of valve should be at least as large as area of suction
pipe – preferably 1-1/2 times. If strainer is used, net clear area should be 3
to 4 times area of suction pipe.
16. Suction inlet not immersed deeply enough
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
17. Wrong direction of rotation
Symptoms are an overloaded drive and about 1/3 rated capacity from
pump. Compare the rotation of the motor with the directional arrow on the
pump casing.
3408A IOM 6/08
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