Faults, Causes And Remedies - Wilo SCPV Installation And Operating Instructions Manual

10 F a u l t s , causes and remedies
Symptoms
-- Pump does not deliver water.
-- Insufficient capacity delivered.
-- Insufficient pressure developed
-- Pump loses prime after starting.
-- Pump requires excessive power.
-- Stuffing box leaks excessively.
-- Pump vibrates or it is noisy.
-- Bearings have short life.
-- Pump overheats and seizes.
Causes
1 Pump not primed
2 Pump or suction pipe not completely filled with
liquid
3 Suction lift too high.
4 Insufficient margin between pressure and vapor Check that NPSH available is at least 1 meter more 1 meter
pressure.
5 Excessive amount of air in liquid.
6 Air pocket in suction line.
7 Air leaks into suction line
8 Air leaks into pump through stuffing boxes.
9 Foot valve too small or leaking.
10 Foot valve partially clogged.
11 Inlet of suction pipe insufficiently submerged.
12 Water seal pipe clogged.
13 Logging ring is improperly located in stuffing
box, preventing sealing fluid from entering to
form seal.
14 Speed too low.
15 Speed too high.
16 Direction of rotating wrong.
17 Total head of system higher than design head of Check the causes and refer to M&P. Measure with pressure
pump.
18 Total head of system lower than pump design
head.
19 Specific gravity of liquid different from design.
20 Viscosity of liquid different from design.
21 0peration at very low capacity.
22 Parallel operation of pumps unsuitable for such Refer to M&P with characteristics curves of pump.
operation.
23 Foreign matter in impeller.
24 Misalignment.
25 Foundations not rigid.
26 Shaft bent.
Installation and operating instructions Wilo – SCV pumps
Possible cause of trouble and remedies
(Each number is defined in the table below)
1,2,3,4,6,11,14,16,17,22,23
2,3,4,5,6,7,8,9,10.11.14.17,20,22,23.29,30,31
5,14,16,17,20,22,29,30,31
2,3,5,6,7,8,11,12,13
15,16,17,18,19,20,23,24.26,27,29,33,34,37
12,13,24,26,32,33,34,35,36,38.39,40
2,3,4,9,10,11,21.23,24,25.26.27,28,30,35,41,42,43, 44,
45,46,47
24,26,27,28,35,36,41,42,43,44,45,46,47
1,4,21,22,24.27,28,35,36,41
Remedies
Ensure that casing is fully filled and water comes out from air-
cock.
Check leaking foot valve in case of negative suction
Reduce by lowering pump elevation or increase Water level.
more than NPSH required.
Check the reasons and eliminate. Gas gets entrapped in liquid.
Air may be entering through suction joints.
Ensure pipe fully filled and there is nobend for negative suction.
Tighten pipe joints with solution.
Ensure stuffing box sealing.
Replace I Attend.
Clean
Ensure adequate submergence such that foot valve is not
exposed.
Clean or change.
Position logging ring centrally under sealing holes of stuffing
box.
Check motor RPM, supply frequency, Motor nameplate speed
should be as specified on pump nameplate.
Check motor RPM and supply frequency.
Check correct direction of rotation for motor before
coupling to motor.
gauge.
Check the causes and refer to M&P. Measure with pressure
gauge.
Refer to M&P.
Refer to M&P
Check the causes and refer to M&P, Operate pump at rated
duty.
Open and clean.
Check with Dial gauge should be within limits and without
undue pipe stresses.
Check, vibration on pump stool, check hollowness.
Dismantle and check, Replace shaft.
29