Goulds Pumps 3498 - IOM - Manual (Page 43)

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.
40
3498 IOM 12/04
Problem Item Probable Cause Remedy
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. Check mechanical seal or packing.
3
Suction lift too high
(a negative suction gauge reading).
If there is no obstruction at inlet and suction valves are open, 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 System static head too high.
Check with factory to see if a larger impeller can be used; otherwise,
cut pipe losses or increase speed — or both, as needed. But be careful
not to seriously overload driver.
5 Speed to low.
Check whether motor is directly across-the-line and receiving full
voltage. 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. If
rotation is correct with arrow, check the relationship of the impeller
with casing. (This will require removing casing upper half.)
7 No rotation. Check power, coupling, line shaft and shaft keys.
8 Impeller loose on shaft. Check key, locknut and set screws.
9 Impeller completely plugged. Dismantle pump and clean impeller.
10
System head or required discharge
head too high. Check pipe friction losses. Large piping may correct condition.
Check that valves are wide open.
No
Liquid
Delivered
11 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. For
such liquids as gasoline, suction line can be tested by shutting off or
plugging inlet and putting line under pressure. A gauge will indicate a
leak with a drop of pressure.
12 Air leaks in stuffing box.
Replace packing and sleeves if appropriate or increase seal lubricant
pressure to above atmosphere.
13 Speed too low. See item 5.
14 Discharge head too high. See item 10.
15 Suction lift too high. See item 3.
16 Impeller partially plugged. See item 9.
17
Cavitation; insufficient NPSHA
(Net Positive Suction Head Available).
a. Increase positive suction head on pump by lowering pump or
increasing suction pipe and fittings size.
b. Sub-cool suction piping at inlet to lower entering liquid
temperature.
c. Pressurize suction vessel.
18 Defective Impeller and/or wear rings.
Inspect impeller and wear rings. Replace if damaged or vane sections
are badly eroded or if wear ring clearance is 3 times normal.
19
Foot valve too small or partially
obstructed.
Area through ports of valve should be at least as large as area of
suction pipe (preferably 1.5 times). If strainer is used, net clear area
should be 3 to 4 times area of suction pipe.
20
Suction inlet not immersed deep
enough.
If inlet cannot be lowered or if eddies through which air is sucked
persists when it is lowered, chain a board to suction pipe. It will be
drawn into eddies, smothering the vortex.
21 Wrong direction of rotation.
Symptoms are an overloaded driver and about one third rated capacity
from pump. Compare rotation of motor with directional arrow on
pump casing. If rotation is correct with arrow, impeller may have to
be turned 180°.
(See CHANGING ROTATION)
22 System head too high. See item 4.
23 Defective mechanical seal. Repair or replace seal.