Plain Bearing Failure - Wear - Scoring damage of white metal thrust pad by dirt

PLAIN BEARING FAILURE

Plain bearing failure index

2.0 Wear

2.1 Scoring damage of white metal thrust pad by dirt

Click on photograph to enlarge
	Scoring of thrust pad by dirt in oil.
Main Characteristics	Score marks follow the direction of motion in the bearing, like the grooves in a gramophone record. The score marks start where the dirt particle bridges the film and form a continuous mark up to the end of the bearing surface, the trailing edge on the right of the pad in the Photograph, or stop with an embedded particle (see following example). Scoring is an example of abrasive wear; adhesive wear gives discontinuous tears rather than clear uninterrupted scores.
Cause	Contamination of the lubricant with hard particles small enough to enter the oil film at the point of maximum film thickness, but too large to pass right through without bridging the film. See also in the photograph how the soft white metal has been dragged over the trailing edge of the pad. See wear summary for further information on causes and actions.
Note	Since the embedded particles can be identified using laboratory methods the source of the contamination can readily be determined.
Possible Confusion with Other Types of Damage	Scoring can lead to a roughening of the bearing surface profile resulting in a potential loss of hydrodynamic film leading to wiping (adhesive wear) which then masks the original source of the problem.
Comment	Scoring damage indicates inadequate filtration of the oil or failure to change the oil filter when necessary.