Goulds Pumps 3408 - IOM - Manual (Page 34)

32
3408 IOM 03/99
Prob lem Item s Prob a ble Cause Rem edy
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 suc tion
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
liq uids as gasoline, suction line can be tested by shutting off or plug ging
in let 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 at mo sphere.
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 in creas ing
suc tion pipe and fittings size.
b. Sub-cool suction piping at inlet to lower entering liquid temperature.
c. Pressurize suction vessel.
18 De fec tive Im pel ler and/or wear rings.
In spect im pel ler and wear rings. Re place if dam aged or vane sec tions
are badly eroded or if wear ring clear ance is 3 times normal.
19 Foot valve too small or par tially ob structed.
Area through ports of valve should be at least as large as area of suc tion
pipe (pref er a bly 1.5 times). If strainer is used, net clear area should be
3 to 4 times area of suc tion pipe.
20 Suc tion in let not im mersed deep enough.
If in let can not be low ered or if ed dies through which air is sucked per sists
when it is low ered, chain a board to suc tion pipe. It will be drawn into
ed dies, smoth er ing the vor tex.
21 Wrong di rec tion of ro ta tion.
Symp toms are an over loaded driver and about one third rated ca pac ity from
pump. Com pare ro ta tion of mo tor with di rec tional ar row on pump cas ing.
If ro ta tion is cor rect with ar row, im pel ler may have to be turned 180º. (see
CHANGING RO TA TION)
22 Sys tem head too high. See item 4.
23 De fec tive me chan i cal seal. Re pair or re place seal.
Not
Enough
Pres sure
24 Speed too low. See item 5.
25 Air leaks in suc tion pip ing or stuff ing box. See item 11.
26 Mechanical de fects. See item 18.
27 Vor tex at suc tion in let. See item 20.
28 Ob struc tion in liq uid pas sages.
Check to see if suc tion and dis charge valves are fully open. Dis man tle
pump and in spect pas sages and cas ing. Re move ob struc tion.
29 Air or gases in liq uid.
May be pos si ble to over rate pump to a point where it will pro vide ad e quate pres -
sure de spite con di tion. Better pro vide gas sep a ra tion cham ber on
suc tion line near pump and pe ri od i cally ex haust ac cu mu lated gas. See item 17.
TROUBLE SHOOTING
Between regular maintenance inspections, be alert for signs of driver or pump trouble. Common symptoms are
listed below. Correct any trouble immediately and AVOID COSTLY REPAIR AND SHUTDOWN.