Section
E41•T41
Page 517
Dated
June 2016
97-4622-01-588
FLEXIBLE COUPLED PUMPS
CLOSE COUPLED PUMPS
VERTICAL FLANGE MOUNTED
PUMPS
A.
Failure to Pump
B.
Reduced Capacity
C.
Reduced Pressure
D.
Pump Loses Prime After Starting
E.
Excessive Power Consumption
F.
Pump Vibrates or is Noisy
G.
Mechanical Problems
H.
Seal Leakage
5A Failure to Pump
1. Pump not up to speed — Use
Tachometer to determine actual
RPM. Check voltage and wiring
connections.
2. Pump not primed — Confirm that
pump and all inlet piping is filled
with fluid.
3. Discharge head too high — Install
a pressure gauge at the pump
discharge to determine the actual
operating pressure. Compare
readings with pump performance
curve. A larger pump may be
necessary.
4. Excessive suction lift — Relocate
pump, supply tank, or both to
minimize suction lift.
5. Wrong direction of rotation
— Compare pump rotation with
arrow on pump. Standard pumps
rotate in a clockwise direction
when looking at the shaft exten-
sion end or from the motor end on
close coupled pumps. Reverse
two leads on a three phase motor
to change rotation. Check motor
nameplate for single phase opera-
tion.
6. Clogged suction line, strainer, or
foot valve — Inspect and clean out
if necessary.
7. Air pocket in suction line — Look
for high spots in inlet piping sys-
tem. Evacuate the system with a
vacuum pump if necessary.
5B Reduced Capacity
1. Pump not up to speed — Use a
tachometer to determine actual
RPM. Check voltage and wiring
connections.
2. Excessive suction lift — Relocate
pump, supply tank, or both to
minimize suction lift.
3. Insufficient NPSH — Relocate
pump, supply tank, or both to
improve NPSH available if pos-
sible. Increase suction pressure.
Reduce fluid temperature. Select
a pump with lower NPSH require-
ments.
4. Mechanical damage — Rotate
the pump by hand to determine if
there are tight spots. Broken or
bent impeller vanes can some-
times be detected in this manner.
If there is a suspicion of damage,
remove the pump from service
and disassemble for inspection.
5. Air leak in the suction line
— Fill the system with fluid and
hydrostatically test. Tighten
connections or replace leaky com-
ponents.
6. Air pockets in the suction pip-
ing — Operating the system at
maximum flow conditions will
usually clear the lines. Evacuate
the system with a vacuum pump if
necessary.
7. Suction lines, strainer, or foot
valve too small or clogged — In-
spect and clean out as necessary.
Fittings and lines should be at
least equal to the pump suction
size.
8. Discharge head too high — Install
a pressure gauge at the pump
discharge to determine the actual
operating pressure. Compare
readings with pump performance
curve. A larger pump may be
necessary.
9. Excessive wear — If a pump had
previously performed satisfacto-
rily and now gives evidence of
reduced performance, it should
be disassembled and examined
for wear after the simpler possible
problems have been investigated.
5C Reduced Pressure:
1. Pump not up to speed — Use a
tachometer to determine actual
RPM. Check voltage and wiring
connections.
2. Air or vapor in liquid — Install
a separator in the suction line.
Check the seal on the inlet end of
the pump to determine if air is be-
ing drawn in. Hydrostatically test
the system to insure that there are
no leaks.
3. Mechanical wear or damage
— Rotate the pump by hand to
determine if there are tight spots.
Broken or bent impeller vanes
can sometimes be detected in this
manner. If there is a suspicion
of damage or wear, remove the
pump from service and disassem-
ble for inspection. Look for wear
on the impeller, suction cover, and
motor bracket.
4. System head less than expected
— Replace pump with higher ca-
pacity unit or add a valve or orifice
to increase line resistance.
5D Pump Loses Prime After
Starting
1. Leak in suction line — Fill the
system with fluid and hydrostati
-
cally test. Tighten connections or
replace leaky components.
2. Air entering pump through inlet
seal or “O” rings — Hydrostati-
cally test the pump and look for
leaks. Replace faulty seals or “O”
rings.
3. Insufficient NPSH or too much
suction lift — Relocate pump, sup-
ply tank, or both to improve inlet
conditions. Increase suction pres-
sure. Reduce fluid temperature.
Select a pump with lower NPSH
requirements.
5.
E41•T41 SERIES
Troubleshooting
