• Over / Under lubrication
• Misalignment
• Improper fit or mounting that causes vibration, creep / scuffing
• Shaft burrs
• Improper bearings selection based on speed , operating temperature or improper seals
• Debris and dust contamination from the environment or in lubricant
• Improper grease / lubricant selection
• Water contamination
• Improper handling ( Bearings will show hitting scar, pressing scar and breaking scars if they are used carelessly and struck forcefully )
• Poor or irregular maintenance

You can learn a lot about a bearings just from its part number.

A typical bearings is the 6203ZZ bearings. This part number can be divided into its components:

62203ZZ which means:

• Suffix
• Bore
• Series
• Type Code

Suffix (62203ZZ)

The last letters indicate something’s special about the bearings, through the suffix. For example:

Bore (62203ZZ)

The last two digits (if there is a suffix, then the digits before it), give details of the bore of the bearings.

For the last two digits being 00, 01, 02, or 03 following are the bore sizes.

• 00 10 mm
• 01 12 mm
• 02 15 mm
• 03 17 mm

For digits beyond 03, the bore size is simply five times the last two digits together.

e.g., if the last two digits are 06 (as in 6206), then the bore size is 06×5=30mm.

If there is no fourth digit – for example, a 608 bearings, a common roller skate bearing – then the size is the last digit in mm. i.e. bore size bearings 608 is 8 mm

Series (62203ZZ)

The digit before the indicating number (the third digit from end), represents the series, which reflects the robustness of the bearings. The series are, from lightest to heaviest:

8 Extra thin section (e.g.6806)

9 Very thin section (e.g.6906)

0 Extra light (e.g.6006)

1 Extra light thrust (e.g.51106)

2 Light (e.g.6206)

3 Medium (e.g.6306)

4 Heavy (e.g.6406)

Type Code (62203ZZ)

The type code indicates the type of bearings. Each manufacturer uses their own numbers. They could be single or double digits or alphabets.

Once a damaged bearing is removed from the machine part, it has to be analyzed to check for the failure so that future mishaps can be avoided. However, it has to be noted that simply inspecting the damaged bearing is not sufficient. A detailed study, inspection, and analysis should be done on mating parts, sealing and the amount of lubrication done.

A proper systematic process should be in place that ensures good removal, making it secure and better for inspection. Following are the steps that need to be taken when a bearing damage occurs:

1. Determining the Operational Data.
2. Evaluating records and the charts from bearing monitoring devices
3. Extracting the lubricant samples.
4. Assessing the bearing mounted conditions
5. Dismount the bearing
6. Make the marking on bearings and its parts
7. Check beating seats
8. Assessment of the complete bearing.

The above is the process for complete damage assessment of the bearing, but wouldn’t be too effective in case the damage is excessive. So early signs of abnormal functioning of the machines should be considered to take proper steps.