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3. Insufficient NPSH or too much
suction lift — Relocate pump,
supply tank, or both to improve
inlet conditions. Increase suction
pressure. Reduce fluid tempera-
ture. 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
discharge 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 neces-
sary.
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 inspection.
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 consump-
tion persists beyond a few
weeks, it is unlikely that further
operation will reduce consump-
tion.
6. Pump not properly adjusted —
Loosen all nuts on pump exactly
one turn. Follow the instructions
in 4G Testing and Final Adjust-
ments for repositioning
fasteners.
5F Pump Vibrates Or Is Noisy
1. Pump and motor are mis-aligned
— Follow the installation
instructions for proper alignment.
2. Insecure mounting — Follow
instructions 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 suspect-
ed, 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 regenera-
tive turbine pump. The intensity
should increase as pressure
increases. Over a period of a
few weeks the noise level will
diminish and will become
noticeably quieter as the pump
approaches a "run in" condition.
5G Mechanical Problems
1. Short bearing life — Bearings
damaged 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. Disas-
sembly and replacement is the
solution if tightening the through
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 micro-
scopic, 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
as a result of 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 backwards.
The smooth surface should face
the rotating element. The
rotating element may be in
backward or improperly posi-
tioned. Refer to the appropriate
seal diagrams and instructions to
confirm the correct seal orienta-
tion. 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 shaft 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 assem-
bly 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.
