Goulds Pumps 3409 - IOM - Manual (Page 36)

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.
36
3409 IOM 11/04
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.
Not Enough
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 (prefer-
ably 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 cor-
rect 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.
Not Enough
Pressure
24 Speed too low. See item 5.
25 Air leaks in suction piping or stuffing box. See item 11.
26 Mechanical defects. See item 18.
27 Vortex at suction inlet. See item 20.
28 Obstruction in liquid passages.
Check to see if suction and discharge valves are fully open. Dismantle pump and in-
spect passages and casing. Remove obstruction.
29 Air or gases in liquid.
May be possible to over rate pump to a point where it will provide adequate pressure de-
spite condition. Better provide gas separation chamber on
suction line near pump and periodically exhaust accumulated gas. See item 17.