JVN BEARINGS FZE
Jebel Ali Free Zone, Dubai,
United Arab Emirates.
Bearings must be carefully handled, mounted, and maintained in order to operate properly. Care and attention must be used during and after installation to increase the work life of the bearing, prevent bearing defects, and reduce the cost of repair and replacement.
In case of poor performance or breakdown, the cause of failure must be determined to prevent repetition. There are three types of data which should be gathered to enable the correct diagnosis of bearing problems:
- Time of occurrence
- Symptoms during operation
- Condition of Bearings
Time of Occurrence
| Time of Occurance / Cause | Bearing Selection | Design or Manufacture of other drive parts | Lubricant Type, System or Amount | Defective Bearing | Bearing Insallation | Seal Failure |
|---|---|---|---|---|---|---|
| Soon After Installation | ✔ | ✔ | ✔ | ✔ | ✔ | |
| Soon after periodic disassembly | ✔ | ✔ | ||||
| Soon After Re-lubrication | ✔ | |||||
| After replacement or repair of other parts | ✔ | ✔ | ||||
| During normal operation | ✔ | ✔ |
Symptoms During Operation
| Operation Condition | Cause | Remarks |
|---|---|---|
| Ever-changing sound | Change of clearance by temperature rise Defect in progress on raceway | |
| Low Level Metallic Sound | Impression on Raceway | |
| High Level Metallic Sound | Loss of Clearance, Poor Lubrication | |
| Irregular Sound | Excess clearance, contaminants, defect of rolling element surface, improper lube | |
| Abnormal temperature rise | Loss of clearance, creep, insufficient or excess lubricant, excess load | Use a surface thermometer. |
| Reduction in accuracy | Raceway or rolling element broken by impurities, or insufficient lubricant | Lathe: stick-slip marks Grinder: wavy pattern Cold roll mill: occulting wave pattern |
| Contaminated lubricant | Poor lubrication, foreign matter, wear | |
| Unstable operation | Broken raceway, rolling element Foreign matter Excess clearance | Example: vibration |
Condition of Bearings & Prevention Methods
| (1) Premature Flaking | ||
| The repeated heavy stress cycle between the bearing raceway and rolling element surface results in fatigue cracks which become loosened from bearing materials. |  | |
| Causes | Counter Measures | |
| Abnormal axial load or excessive load caused by expanded shaft. | Clearance fit for the outer ring of one bearing to allow the floating end to move freely axially. | |
| Deflection or misalignment of shaft. | Correct alignment of shaft and bearing housing. | |
| Poor parallelism of inner and outer rings. | Improve mounting and alignment. | |
| Poor lubrication. | Carefully clean and handle shaft and housing. | |
| Rusting, Nicks, Galling from dirt, etc. | Review type and quantity of lubricant. | |
| (2) Seizure | ||
| Bearing is seized up by excessive heat. Discoloration, softening and fusion of raceway and rolling element. |  | |
| Causes | Counter Measures | |
| 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 | Counter Measures | |
| 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) Indentation | ||
| Brinelling, indentation and pear skin of bearing raceway and rolling |  | |
| element. | ||
| Causes | Counter Measures | |
| 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 conditions. | |
| (5) Fretting | ||
| Occurs when a small relative motion is repeatedly caused in non-rotating bearing. Fretting surface wear produces red colored particles at fitting surface. |  | |
| Causes | Counter Measures | |
| Vibration applied to bearing at rest (e.g. during shipment). | Fit 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) Scoring | ||
| Metal to metal contact of bearing raceway, flange face, rolling element and retainer due to destruction of oil film. |  | |
| Causes | Counter Measures | |
| Incorrect lubrication. | Review type and quantity of lubricant. | |
| Contamination by foreign matter. | Improve sealing and component cleaning. | |
| Deflection or misalignment of shaft. Excessive axial load. | Correct mounting errors. Review load conditions. | |
| Sharp speed increase at startup. | Change to smooth acceleration. | |
| (7) Smearing | ||
| Metal to metal contact due to the destruction of oil film. Sliding motion between outer/inner ring and rolling element. |  | |
| Causes | Counter Measures | |
| Excess axial load. | Correct mounting errors. | |
| Misalignment of bearing. | Review the load condition. | |
| Poor lubrication. | Select a proper lubricant, and feed it in proper quantity. | |
| Intrusion and galling caused by foreign matter. | Improve the sealing. | |
| High acceleration on start-up. | Clean shaft and housing. | |
| Avoid sharp acceleration. |
