Neale Consulting Engineers - Services - Failure Investigation - Cavitation Erosion

PLAIN BEARING FAILURE

Plain bearing failure index

4.0 Cavitation Erosion

Cavitation Erosion Index

4.3 Cavitation Erosion of White Metal Thrust Collar

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	Photograph a: cavitation erosion of white metal thrust face
	Photograph b: steel thrust collar with lubricant feed grooves on end of shaft
Main Characteristics	Photograph 'a' shows typical roughening of white metal caused by erosion.
Cause	Photograph 'b' shows the thrust collar associated with the cavitation damage shown in Photograph 'a'. This is an unusual arrangement with the radial oil grooves machined in the hard steel thrust collar, the reverse of the more normal arrangement with the grooves in the soft white metal.
Note
Possible Confusion with Other Types of Damage
Comment	The problem was caused by the sharp fall in pressure at the beginning of the grooves in the steel collar, followed by bubble collapse as the oil re-entered the high pressure region downstream of the groove. The problem was solved by changing to the more normal arrangement with the grooves in the white metal face.