62 | Flameproof motors
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TROUBLESHOOTING CHART ABOUT BEARINGS
NOTE
This troubleshooting chart provides a basic list of unusual cases that may occur on bearings
during motor operation, possible causes and recommended corrective actions. For certain
cases, bearing manufacturer is required in order to identify the root cause of the defect.
Table 10-2 - Basic listing of problems with bearings
Abnormality
Possible causes
Correction actions
Motor is noisy while in
operation.
Damaged bearings;
Replace the bearing;
Moderate noises on the
bearing, coloring spots,
grooves on the races.
Bearing was assembled in diagonal;
Recover the shaft seat and replace the
bearing;
Excessive bearing noise and
higher bearing heating.
Corrosion on the squirrel cage, small chips in the
grease, failure on the races due to the lack of
grease, eventually incorrect bearing clearance;
Clean and regrease according to
instructions;
Replace the bearing;
Bearing overheating
Excess of grease;
Remove the grease drain plug and let the
motor run until the excess of grease comes
out;
Excessive axial or radial load;
Decrease the belt-tension;
Unsatisfactory engagement of connecting gears.
To be reconditioned.
Bent shaft / excessive vibration;
Correct the shaft and check the rotor
balance. Check the source of the vibration
and correct it;
Lack of grease;
Add grease to the bearing;
Hardening of grease results in locking of rolling
elements;
Replace the bearings;
Foreign body in the grease;
Wash the bearings and lubricate;
Dark spots on one side of the
bearing race resulting in
further grooves.
Excessive axial force;
Check the drive and coupling ratio;
Dark lines on the races or
intensive diagonal grooves;
In case of ball bearings, point
form marks.
Current circulation through the bearings;
Clean and replace the bearing insulation.
Apply insulation, if there isn’t any;
Avoid the current to go through the bearing;
Hits on the races, previously
clear.
Grooves between rolling
elements.
External vibrations mainly when the
motor remains at standstill for a long period;
From time to time rotate the rotor of the
motor at standstill to another position,
mainly if it is a spare motor;
Lack of maintenance while in storage;