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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
Issued by: MOLM
Sheet No.
3AAM101036 E
Rev. B
Page
5 of 8
01.2023
W
e
reserve
a
ll
rig
ht
s i
n t
his
do
cument an
d in t
he
inf
orm
at
ion
con
tai
n
e
d
the
rein.
R
ep
ro
duct
ion
,
use of
disclos
u
re
t
o t
h
ird
pa
rti
es wit
ho
ut
expr
ess
au
th
or
ity
is
s
tric
tly
for
bidden.
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
B
Noisy bearing
C
Too frequent replacement
D
High vibration level
E
Unsatisfactory equipment performance
F
Bearing loose on the shaft
G
Shaft is difficult to turn
SYMPTOMS
Typical cause
Defect
Solution
A B C D E F G
x x x
x
Inadequate
lubrication.
Grease of wrong type for
the operating conditions.
Consult
grease
manufacturer
to
determine the proper type of lubricant
Check miscibility if grease has been
changed from one type to another.
x x x
x
Inadequate
lubrication.
Insufficient grease in the
bearing housing.
Fill housing 1/3 to 1/2 with grease.
x
x
Excessive
lubrication.
Housing is excessively
packed with grease.
Purge bearing housing until it is 1/2 filled
with grease.
x x x
x
x
Insufficient bearing
clearance.
Bearing has inadequate
internal clearance for the
temperature caused by the
heat conducted through
the shaft.
Check weather the bearing had
clearance according to the rating plate of
the machine. If not mount a bearing
according the rating plate.
x x x x
x
Foreign matter
acting as abrasive.
Dirt, sand, carbon or other
contaminants are entering
the bearing housing.
Clean the bearing housing. Replace
worn seals or improve the seal design to
obtain adequate protection.
x x x x
x
Foreign matter
acting as corrosive.
Water, acids, paints or
other
corrosives
are
entering
the
bearing
housing.
Install a protective shield and/or fingers
to guard against foreign matter. Improve
seals.
x x x x
x
Foreign matter in
the bearing
housing.
Chips, dirt, etc. were not
removed from housing
before assembling the
bearing unit.
Carefully clean and fill with new
lubricant.
x x x
x
Bearing
excessively
preloaded.
Two locked bearings on
the shaft. Insufficient axial
float caused by excessive
shaft expansion.
Check the “free” bearing: Improve the
possibility for shaft expansion by
machining the outer bearing cover.
x x x x x
Outer ring spins in
the housing.
Unbalanced load.
Rebalance the machine or the shaft line.
x
x x
Noisy bearing.
Flat spot on rolling
elements due to skidding.
Visually check the rolling elements and
replace the bearing if elements have flat
spot. Make sure that the required
minimum load is applied to the bearing.
x
x x x
x
Linear and/or
angular
misalignment of
the shaft.
Incorrect alignment of the
shaft line during coupling.
Correct alignment by shimming the
motor. Ensure that the shafts are
coupled in a straight line. Be sure to
use full support shims.
x x x x
Rolling elements
are dented.
Incorrect mounting
method. Hammer blows
on the bearing.
Replace the bearing with a new one.
Never hammer any part of bearing when
mounting. Always heat up the bearing for
mounting.
x
x x
High vibrations.
Excessive clearance of the
bearing.
Use bearing with the prescribed internal
clearance.
x
x x
High vibrations.
Equipment is vibrating.
Check the balance of the rotating parts.
Rebalance the equipment.
Check the stiffness of the foundation.
x
Bearing is
discoloured.
Distortion of the shaft and
other bearing assembly
components, probably due
to heat.
Avoid high heat concentration at any
point of the bearing to avoid distortion.
Replace discoloured bearing.