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and now gives evidence of reduced
performance, it should be disassem-
bled 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 being 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 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
increase 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
suction lift — Relocate pump, supply
tank, or both to improve inlet
conditions. Increase suction
pressure. Reduce fluid temperature.
Select a pump with lower NPSH
requirements.
5E Excessive Power Consumption
1. Speed too high — Check RPM with
tachometer.
2. Discharge head too high — Install a
pressure gauge at the disharge to
determine the actual operating
pressure. Compare readings with
pump performance curve. A
different 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 case, run the
pump for a few hours before checking
for tight spots. If there is a suspicion
of damage, remove the pump from
service and disassemble for inspec-
tion.
5. Pump not fully “broken in” — It is
normal for new pumps to consume
higher than normal current during the
break-in period. If high power
consumption persists beyond a few
weeks, it is unlikely that further
operation will reduce consumption.
6. Pump not properly adjusted — Loosen
all nuts on pump exactly one turn.
Follow the instructions in Section 4F
Testing and Final Adjustments, for
repositioning fasteners.
5F Pump Vibrates Or Is Noisy
1. Pump and motor are misaligned —
Follow the instructions in Section 2D
Alignment, for proper alignment.
2. Insecure mounting — Follow instruc-
tions in Section 2, 2B Foundation.
3. Piping load on pump — Install piping
supports and check to see that there is
no strain on the pump.
4. Mechanical damage — If mechanical
damage is suspected, check first to
determine if the pump turns freely.
Disassemble for inspection if tight
spots are found.
5. Pump has a high pitched whine — This
is typical of a regenerative turbine
pump. The intensity should increase
as pressure increases. Over a period
of a few weeks the noise level will
diminish and will be noticeably quieter
as it approaches a “run-in” condition.
5G Mechanical Problems
1. Short bearing life — Bearings dam-
aged due to leaky seals. Coupling
misalignment. Piping load on pump.
RPM or pump pressure too high.
2. Pump locked up — Pump dried out
and close clearance areas rusted.
Follow installation instructions for
loosening the pump. Foreign material
in pump. Flush out. Disassemble if
flushing is not successful.
3. Pump leaks — Seal or “O” rings are
usually the problem. Disassembly
and replacement is the solution if
tightening the thru bolts has no
effect.
5H Seal Leakage
1. Worn seat or rotating element —
Seals will last many years operating
on cold clear water or other fluids
with reasonable lubricity. Particles,
even microscopic, increase normal
wear rates. Temperatures near the
fluid's boiling point can reduce
lubricity which in turn increases
wear. Some chemicals will erode
the seal faces or plate out on the
faces producing an abrasive effect.
Immediate seal replacement is
recommended when leaks become
evident, since bearings are quickly
ruined when exposed to moisture.
Severe mechanical damage results
when the bearings fail.
2. Improperly installed seat or rotating
element — If a seal has recently
been replaced, look for a missing “O”
ring/cup around the seat, or a seat
that was installed cocked or back-
wards. The smooth surface should
face the rotating element. The
rotating element may be in backward
or improperly positioned. Refer to
the appropriate seal diagrams and
instructions to confirm the correct
seal orientation. Rotating elements
sometimes stick in the wrong
position if left partially assembled for
some time. Make sure a rotating
element can be moved axially on the
shaft before closing up the pump,
and then make the final adjustments
as soon as possible.
3. Seat broken during assembly —
Ceramic seats are particularly
vulnerable to damage. Carefully
follow reassembly instructions for
seals. Seals on flex-coupled units
can be damaged by excessive
hammering when installing the
coupling onto the shaft extension.
4. Pitted shaft under the seal —
Reusing a shaft or sleeve when
repairing a pump is the probable
cause of this problem. The seal
rotating element can produce a
pitted surface underneath its
elastomer portion during normal use.
This is normally not a problem for the
first seal assembly since the
elastomer is conforming as this
action occurs. A new seal can leak
before it conforms if the pits are
large enough. If any pits are visible
to the unaided eye, shaft or sleeve
replacement is advised.
