![background image](http://html.mh-extra.com/html/mth-pumps/t31-series/t31-series_manual_1852018014.webp)
T31 SERIES
Troubleshooting
2. Excessive suction lift —
Relocate pump, supply tank, or both
to minimize suction lift.
3. Insuffi cient NPSH —
Relocate pump, supply tank, or
both to improve NPSH available if
possible. Increase suction pressure.
Reduce fl uid 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
sometimes be noticed in this man-
ner. If there is suspicion of damage,
remove the pump from service and
disassemble for inspection.
5. Air leak in the suction line —
Fill the system with fl uid and hydro-
statically test. Tighten connections
or replace leaky components.
6. Air pockets in the suction piping —
Operating the system at maximum
fl ow 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 per-
formed satisfactorily and now gives
evidence of reduced performance,
it should be disassembled and
examined for wear after the simpler
possible problems have been pur-
sued.
6C Reduced Pressure
1. Pump not up to speed —
Use a tachometer to determine ac-
tual RPM. Check voltage and wiring
connections.
2. Air or vapor in liquid —
Install a separator in the suction line.
Hydrostatically test the system to
insure that there are no leaks.
3. Mechanical wear or damage —
Rotate the pump by hand to deter-
mine if there are tight spots. Broken
or bent impeller vanes can some-
times be noticed in this manner. If
there is suspicion of damage or
wear, remove the pump from service
and disassemble for inspection.
Look for wear on the impeller, suc-
tion cover, and motor bracket.
4. System head less than expected —
Replace pump with higher capac-
ity unit or add a valve or orifi ce to
increase line resistance.
6D Pump Loses Prime After Starting
1. Leak in suction line —
Fill the system with fl uid and hydro-
statically test. Tighten connections
or replace leaky components.
2. Air entering pump through
“O” rings —
Hydrostatically test the pump looking
for leaks. Replace faulty “O” rings.
3. Insuffi cient NPSH or too much
suction lift —
Relocate pump, supply tank, or both
to improve inlet conditions. Increase
suction pressure. Reduce fl uid tem-
perature. Select a pump with lower
NPSH requirements.
6E 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 read-
ings with pump performance curve.
A different pump, motor or both may
be necessary.
3. Specifi c gravity or viscosity too high
—
Check fl uid involved. A different mo-
tor 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
6.
CLOSE COUPLED 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
6A Failure to Pump
1. Pump not up to speed —
Use tachometer to determine actual
RPM. Check voltage and wiring
connections.
2. Pump not primed —
Confi rm that pump and all inlet pip-
ing is fi lled with fl uid.
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 minimize suction lift.
5. Wrong direction of rotation—
Compare pump rotation with arrow
on pump. Standard pumps rotate in
a counterclockwise direction when
looking at the shaft extension end.
Clockwise 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
system. Evacuate the system with a
vacuum pump if necessary.
6B Reduced Capacity
1. Pump not up to speed —
Use a tachometer to determine ac-
tual RPM. Check voltage and wiring
connections.
Page 514