Section
140 • 180
Page 512
Dated
October 2011
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
and channel rings.
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 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
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 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
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 5F 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
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 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
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.
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 backwards. 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
