13. Bearing failures and countermeasures
When a bearing is used under ideal conditions, it will only be damaged by rolling fatigue. Damage due to rolling fatigue may occur very early, however.
If damage is found on a bearing, it is important to examine the phenomenon properly and identify the causes, even if the damage is very small. In addition, it is essential to examine it comprehensively, checking not only the bearing but also the shaft, housing and lubricant.
To identify the cause of the bearing damage, it is required to have sufficient knowledge and expertise regarding bearings and lubrication, to be familiar with the characteristics of the application machine, and to be well informed of the conditions under which the bearing is installed and of the past records of the machine operation.


1. Flaking
Failures Damages Causes Countermeasures
[Flaking]

Flaking is a phenomenon when material is removed in flakes from a surface layer of the bearing raceways or rolling elements due to rolling fatigue.
This phenomenon is generally attributed to the approaching end of bearing service life. However, if flaking occurs at early stages of bearing service life, it is necessary to determine causes and adopt countermeasures.

[Reference; Pitting]
Pitting is another type of failure caused by rolling fatigue, in which minute holes of approx.0.1 mm in depth are generated on the raceway surface.
Flaking occurring at an incipient stage
Too small internal clearance
Improper or insufficient lubricant
Too much load
Rust
Provide proper internal clearance.
Select proper lubricating method or lubricant.
Flaking on one side of radial bearing raceway
Extraordinarily large axial load
Fitting between outer ring on the free side and housing should be changed to clearance fit.
Symmetrical flaking along circumference of raceway
Inaccurate housing roundness
Correct processing accuracy of housing bore.
  (Especially for split housings, care should be taken to ensure processing accuracy.)
Slanted flaking on the radial ball bearing raceway
Improper mounting
Shaft deflection
Inaccuracy of the shaft and housing
Correct centering.
Widen bearing internal clearance.
Correct squareness of shaft or housing shoulder.
Flaking occurring near the edge of the raceway or rolling contact surface of roller bearings
Flaking on the raceway surface at the same interval as rolling element spacing
Heavy impact load during mounting
A flaw of cylindrical roller bearings or tapered roller bearings caused when they are mounted.
Rust gathered while out of operation.
Improve mounting procedure.
Provide rust prevention treatment before long cessation of operation.