Neale Consulting Engineers - Services - Failure Investigation - Cavitation Erosion

PLAIN BEARING FAILURE

Plain bearing failure index

4.0 Cavitation Erosion

Cavitation Erosion Index

4.4 Cavitation Damage Caused by Bearing Instability

Click on photograph to enlarge
	Photograph a: cavitation erosion damage to white metal journal bearing in high-speed refrigeration compressor subject to instability
	Photograph b: part of Photograph 'a' at higher magnification
Main Characteristics	This is another aspect of cavitation erosion damage, in this case the bearing of a high-speed (25,000 rev/min) refrigeration compressor that was subject to a synchronous vibration. The higher magnification Photograph 'b' shows erosion damage resembling the effect of wave action on a sandy shore.
Cause	The refrigerant was Refrigerant R12 that was in contact with the lubricating oil. Because of the vibration, the refrigerant came out of solution in the oil as the shaft moved away from the bearing, only to go back into solution as the pressure increased as the shaft approached the bearing.
Note	This was a case of gaseous cavitation, giving a less energetic bubble collapse, but sufficiently energetic to cause cavitation damage to the bearings.
Possible Confusion with Other Types of Damage
Comment	For another example where gaseous cavitation was involved, see Section 6 "Copper Deposit on Thrust bearing".