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