TROUBLE-SHOOTING BEARING PROBLEMS


Rolling Contact Bearings must be carefully handled, mounted, and maintained in order to operate satisfactorily.

The cause of unsatisfactory operation must be determined to prevent recurrence. There are three cate , gories of data which should be gathered to enable the correct diagnosis of Bearing problems :

* Time of occurrence.
* Symptoms during operation.
* Condition of Bearing.

Although the origin of Bearing problems can sometimes be determined using data from only one of the data categories, quick and accurate analysis requires as much data as possible.

1.   Premature Flaking
The repeated heavy stress cycle between the Bearing raceway and rolling element in fatigue cracks which become loosened from Bearing materials.
Causes Countermeasures
Abnormal axial load or excessive load caused by expanded shaft. Clearance fit for the outer ring of one Bearing to allow to move freely axially for floating end.
Deflection or misalignment of shaft. Correct accuracy of shaft and Bearing housing.
Poor parallelism of inner and outer rings. Improve mounting and alignment.
Poor lubrication. Review type and quantity of lubricant.
Rusting, Nicks, Galling from dirt, etc. Carefully clean and handle shaft and housing.
2.   Seizure
Bearing is seized up by excessive heat. Discoloration, softenning and fusion of iaceway and rolling element.
Causes Countermeasures
Loss of clearance Review fitting and Bearing clearance.
Operating over limiting speed Review type of Bearing.
Poor or improper lubricant. Select a proper lubricant, and feed it in proper quantity.
3.   Breakage
Splits and cracks in the inner/outer ring or rolling element.
Causes Countermeasures
Excessive interference fit. Check fits. Finish shaft and sleeve to higher accuracy.
Bearing seat has larger corner radius than Bearing. Make shaft corner radius smaller than that of the Bearing.
Excess clearance during operation. Check fits and Bearing clearance.
Excess impact load. Re-check load conditions.
4.   Brinelling
Brinelling, indentation and pear skin of Bearing raceway and rolling element.
Causes Countermeasures
Impact applied during mounting. Carefully handle the Bearing.
Impact from dropped Bearing. Clean shaft and housing.
Contamination. Improve the sealing.
Load applied to Bearing at rest in excess of static load rating. Re-check load condition.
5.   Fretting
Occurred when a small relative motion is repeatedly caused in non rotating Bearing. Fretting surface wear producing red colored particles at fitting surface.
Causes Countermeasures
Vibration applied to Bearing at rest (e.g. during shipment) Fix the shaft and housing during shipment.
Swing with smaller amplitude. Apply a preload. Use oil for lubrication.
Minute clearance on fit surface. Increase the interference.
Slight sliding during operation as a result reduced interference under a load. Apply oil.
6.   Smearing
Metal to metal contact due to the destruction of oil film. Sliding motion between outer/ inner ring and rolling element.
Causes Countermeasures
Excess axial load. Misaligment of Bearing. Correct mounting errors.
Poor lubrication. Review the load condition.
Intrusion and galling of foreign matter. Select a proper lubricant and feed it in proper quantity.
High acceleration on start-up. Improve the sealing.
  Clean shaft and housing.
  Avoid sharp acceleration.
7.   Excessive Wear
Abnormal wear of flange face, rolling element and retainer.
Causes Countermeasures
Foreign matter and corrosion acting as lapping agent. Improve sealing.
Insufficient or incorrect lubricant. Clean shaft and housing
  Check lubricant for type and amount.
8.   Rusting, Corrosion
Rusting and corrosion of Bearing ring and rolling element surface.
Causes Countermeasures
Improper storage, cleaning. Improve storage and handling.
Improper washing oil. Re-check washing oil.
Poor rust prevention. Review rust prevention.
Corrosive gas, liquid or water. Improve sealing.
Handling with unprotected hand. Correct handling.
Chemical action of lubricant. Check lubricant.
9.   Creep
Galling, wear, sliding and discoloration of fit face.
Causes Countermeasures
Insufficient interference. Check fits.
Insufficient tightened sleeve. Tighten sleeve
Insufficient surface pressure due to low rigidity and inaccurate shaft and housing. Redesign for greater rigidity.


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