2. Excessive suction lift — Relocate
pump, supply tank or both to mini-
mize suction lift.
3. Insufficient NPSH — Relocate
pump, supply tank or both to im-
prove NPSH available if possible.
Increase suction pressure. Reduce
fluid temperature. Select a pump
with lower NPSH requirements.
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 components.
6. Air pockets in the suction piping —
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 — Inspect 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 read-
ings with pump performance curve.
A larger pump may be necessary.
9. Excessive wear — If a pump had
previously performed satisfactorily
and now gives evidence of reduced
performance, it should be disas-
sembled 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 sep-
arator in the suction line. Check the
seal on the inlet end of the pump to
determine if air is being drawn in.
Hydrostatically test the system to
insure that there are no leaks.
3. Mechanical wear or damage — Ro-
tate 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
disassemble for inspection. Look
for wear on the impeller, suction
cover, and motor bracket.
4. System head less than expected —
Replace pump with higher capacity
unit or add a valve or orifice to in
-
crease line resistance.
5D Pump Loses Prime After Starting
1. Leak in suction line — Fill the
system with fluid and hydrostatically
test. Tighten connections or replace
leaky components.
2. Air entering pump through inlet
seal or “O” rings — Hydrostatically
test the pump and look for leaks.
Replace faulty seals or “O” rings.
3. Insufficient NPSH or too much suc
-
tion lift — Relocate pump, supply
tank, or both to improve inlet con-
ditions. Increase suction pressure.
Reduce fluid temperature. Select
a pump with lower NPSH require-
ments.
5E Excessive Power Consumption
1. Speed too high — Check RPM with
tachometer.
2. Discharge head too high — Install
a pressure gauge at the discharge
to determine the actual operating
pressure. Compare readings with
pump performance curve. A differ-
ent pump, motor, or both may be
necessary.
3. Specific gravity or viscosity too high
— Check fluid involved. A different
motor may be necessary.
4. Mechanical damage — Turn pump
over by hand. After a few days run
in period, all models should turn
over by hand with no tight spots. An
exception to this is when the pump
has been idle for some time. In this
5.
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 ta-
chometer to determine actual RPM.
Check voltage and wiring connec-
tions.
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 read-
ings with pump performance curve.
A larger pump may be necessary.
4. Excessive suction lift — Relocate
pump, supply tank, or both to mini-
mize suction lift.
5. Wrong direction of rotation — Com-
pare pump rotation with arrow on
pump. Standard pumps rotate in a
clockwise direction when looking at
the shaft extension 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
operation.
6. Clogged suction line, strainer or
valve — Inspect and clean out if
necessary.
7. Air pocket in suction line — Look
for high spots in inlet piping system.
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.
Section
T51 • E51
Page 518
Dated
February 2014
Troubleshooting
T51 • E51 SERIES
