Calculating Required Minimum Load for Cylindrical Roller Bearings

Large sliding is generated on the contact surface of a cylindrical roller bearing that is operating under very light loads due to the lack of effective contact surface pressure between the rolling elements and raceways.

Such sliding damage, which acts upon the raceway, ultimately results in bearing seizure.

In order to ensure proper bearing operating conditions, NSK recommends applying a minimum load (Frm or higher amount) to the bearing during operations.

The required minimum load (Frm) is based on the relationbetween frictional force generated on the contact surface of the bearing’s rolling elements and the resistance force of oil lubricant.

Figure below illustrates the required minimum load for an NU208ET cylindrical roller bearing.

Figure Required minimum load for NU208ET cylindrical roller bearing

Cautionary Notes

Do not use the calculated minimum load discussed above for cylindrical roller bearings that meet any of the following conditions:

     1. Bearings with a bore diameter exceeding 130 mm.

     2. Bearings not having a normal clearance (CN).

     3. Bearings not mounted in stationary housing or not mounted on a horizontal rotating shaft.

     4. High-speed operations exceed limiting speeds.

     5. Bearings are subjected to axial loads.

     6. Oil level does not reach the center of the rolling element in the lowest position under oil-bath lubrication.

     7. Lubrication is not oil-bath or forced-circulation oil lubrication (i.e. grease lubrication, drip-feed lubrication, oil-splash lubrication, oil-mist lubrication).

     8. Drainage is insufficient under forced-circulation oil lubrication.

     9. Bearing or lubricant is contaminated with water or particles of degraded lubricant.

     10. Bearings are exposed to excessive vibrations.

     11. A large misalignment exists between the bearing’s inner and outer rings.

     12. Bearings are suffering from abnormal wear, corrosion, electric erosion, etc.