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Installation, operation and maintenance instructions
High voltage flameproof motors for explosive atmosphere
AMD Rg 355-400-450-500
Operating faults – Trouble shooting information for Squirrel Cage Induction
motors
F) Faults of the antifriction bearings (balls or rolls)
The following table is taken from the "SKF" bearings maintenance manual. The fault symptoms are classified
in accordance to the codes:
A
Overheating
D
High vibration level
F
Bearing loose on the shaft
A B C D E F G
x x x
x x x
x
x x x
x x x x
x x x x
x x x x
x x x
x x x x x
x
x
x x x x
x
x
x
SYMPTOMS
Typical cause
x
Inadequate
lubrication.
x
Inadequate
lubrication.
x
Excessive
lubrication.
x
x
Insufficient bearing
clearance.
x
Foreign matter
acting as abrasive.
x
Foreign matter
acting as corrosive.
x
Foreign matter in
the bearing
housing.
x
Bearing
excessively
preloaded.
Outer ring spins in
the housing.
x x
Noisy bearing.
x x x
x
Linear and/or
angular
misalignment of
the shaft.
Rolling elements
are dented.
x x
High vibrations.
x x
High vibrations.
Bearing is
discoloured.
B Noisy bearing
C Too frequent replacement
E Unsatisfactory equipment performance
G Shaft is difficult to turn
Defect
Grease of wrong type for
Consult
the operating conditions.
determine the proper type of lubricant
Check miscibility if grease has been
changed from one type to another.
Insufficient grease in the
Fill housing 1/3 to 1/2 with grease.
bearing housing.
Housing is excessively
Purge bearing housing until it is 1/2 filled
packed with grease.
with grease.
Bearing has inadequate
Check
internal clearance for the
clearance according to the rating plate of
temperature caused by the
the machine. If not mount a bearing
heat conducted through
according the rating plate.
the shaft.
Dirt, sand, carbon or other
Clean the bearing housing. Replace
contaminants are entering
worn seals or improve the seal design to
the bearing housing.
obtain adequate protection.
Water, acids, paints or
Install a protective shield and/or fingers
other
corrosives
are
to guard against foreign matter. Improve
entering
the
bearing
seals.
housing.
Chips, dirt, etc. were not
Carefully
removed
from
housing
lubricant.
before
assembling
the
bearing unit.
Two locked bearings on
Check the "free" bearing: Improve the
the shaft. Insufficient axial
possibility
float caused by excessive
machining the outer bearing cover.
shaft expansion.
Unbalanced load.
Rebalance the machine or the shaft line.
Flat spot on rolling
Visually check the rolling elements and
elements due to skidding.
replace the bearing if elements have flat
spot. Make sure that the required
minimum load is applied to the bearing.
Incorrect alignment of the
Correct alignment by shimming the
shaft line during coupling.
motor. Ensure that the shafts are
coupled in a straight line. Be sure to
use full support shims.
Incorrect mounting
Replace the bearing with a new one.
method. Hammer blows
Never hammer any part of bearing when
on the bearing.
mounting. Always heat up the bearing for
mounting.
Excessive clearance of the
Use bearing with the prescribed internal
bearing.
clearance.
Equipment is vibrating.
Check the balance of the rotating parts.
Rebalance the equipment.
Check the stiffness of the foundation.
Distortion of the shaft and
Avoid high heat concentration at any
other
bearing assembly
point of the bearing to avoid distortion.
components, probably due
Replace discoloured bearing.
to heat.
Sheet No.
3AAM101036 E
Rev. B
01.2023
5 of 8
Page
Solution
grease
manufacturer
to
weather
the
bearing
had
clean
and
fill
with
new
for
shaft
expansion
by
Issued by: MOLM
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