suspicion of damage or wear,
remove the pump from service
and disassemble for inspection.
Look for wear on the impeller
4. System head less than expected
— Replace pump with higher
capacity unit or add a valve
or orifi ce to increase line
5D Pump Loses Prime After
1. Leak in suction line — Fill
the system with fl uid and
hydrostatically test. Tighten
connections or replace leaky
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. Insuffi cient NPSH or too much
suction lift — Relocate pump,
supply tank, or both to improve
inlet conditions. Increase
suction pressure. Reduce fl uid
temperature. Select a pump with
5E Excessive Power Consumption
1. Speed too high — Check RPM
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
3. Specifi c gravity or viscosity too
high — Check fl uid involved.
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
normal current during the
break-in period. If high power
consumption persists beyond
a few weeks, it is unlikely that
further operation will reduce
6. Pump not properly adjusted —
one turn. Follow the instructions
in Section 4F Testing and Final
Adjustments, for repositioning
5F Pump Vibrates Or Is Noisy
1. Pump and motor are misaligned
— Follow the instructions in
Section 2D Alignment, for proper
2. Insecure mounting — Follow
instructions in Section 2, 2B
3. Piping load on pump — Install
piping supports and check to
see that there is no strain on the
is suspected, check fi rst to
determine if the pump turns
inspection if tight spots are
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.
1. Short bearing life — Bearings
damaged due to leaky seals.
Coupling misalignment. Piping
load on pump. RPM or pump
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 fl ushing is not successful.
3. Pump leaks — Seal or “O”
rings are usually the problem.
Disassembly and replacement is
the solution if tightening the thru
1. Worn seat or rotating element
— Seals will last many years
operating on cold clear water
or other fl uids with reasonable
lubricity. Particles, even
microscopic, increase normal
near the fl uid’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
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
rotating element. The rotating
element may be in backward or
improperly positioned. Refer to
the appropriate seal diagrams
and instructions to confi rm 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 fi nal adjustments as
3. Seat broken during assembly
— Ceramic seats are particularly
vulnerable to damage. Carefully
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