Symptom
Cause
Remedy
Piping not properly anchored
Check to see if excessive pipe strain
is being transferred to pump flanges
Pump and/or driver not secured to
sub-base
Check fasteners, if loose check align-
ment and re-tighten
Specific gravity higher than specified Analyze pumpage and compare to
specified gravity
Viscosity higher than specified
Analyze pumpage and compare to
specified viscosity
Pump assembled incorrectly
Compare pump assembly to instruc-
tion manual
Partly clogged impeller causing Im-
balance
Back flush pump or manually clean
impeller
Pump is noisy or vibrates at higher
than normal levels
Broken or bent impeller or shaft
Replace as required
Pump foundation not rigid or sub-
base not completely secured
Tighten hold down bolts on sub-base
Check foundation rigidity
Impeller out of balance
Check impeller balance
Motor not secure
Check motor fasteners
Improper coupling lubrication
Check coupling lubrication schedule
in manufacturers installation, opera-
tion, maintenance manual
Bearing incorrectly installed
Check bearing orientation to sectional
drawing
Coupling out of balance
Check pump and drive component vi-
bration levels, rebalance coupling if
necessary
Pump operating speed too close to
system’s natural frequency
Change speed to be +/- 20% of the
pumps natural frequency
Impeller partly clogged
Back flush pump or manually clean
impeller
Impeller clearances too tight
Check impeller clearances adjust if
necessary
Pump assembled incorrectly
Compare pump assembly to instruc-
tion manual
Pump run off design point
Check head and flow, AF’s should
normally be run between 75% and
125% of BEP
Excessive shaft deflection
Check shaft diameter, sag and deflec-
tion, consult factory
Worn bearings
Replace
Suction or discharge piping not anch-
ored or properly supported
Anchor per Hydraulic Institute Stran-
dards Manual recommendation
Suction and/or discharge valve
closed or clogged
Open valves to remove partially
blocked condition
Excessive shaft misalignment
Check shaft run-out and consult fac-
tory
Pump assembled incorrectly
Compare pump assembly to instruc-
tion manual
Pump is cavitating, insufficient NPSH
available
System problem, increase liquid level
or lower pump
High rate of mechanical seal failure
Insufficient NPSH available
Increase liquid level or lower pump
Excessive shaft misalignment
Check shaft run-out and consult fac-
tory
7.1 Pump Troubleshooting
Model AF (42"/1200mm/54"/60"/66") LM/LMR Bearings Installation, Operation, and Maintenance Manual
63