WIPING OF BEARING SURFACES
A wiped bearing surface is where surface rubbing, melting and smearing is evident. This is usually due to inadequate running clearance with consequent surface overheating, or may be due to inadequate oil supply, or both these causes.
A wiped surface may follow disruption of the oil film due to extreme loading; and shaft vibrations due to excessive imbalance or journal instability are other causes.
Fig. 32 - Whitemetal-lined turbine bearing, wiped in both top and bottom halves due to inadequate clearance.
Fig. 33 - Overlay-plated copper lead bearing wiped due to barrelled journal.
If lightly wiped, re-fit bearing after cleaning surface to remove any loose metal, providing the clearance can be tolerated. If cracked, fit new bearing and increase the clearance when fitting. If vibration present,
(a) synchronous with shaft rotational frequency; check balance of rotor, alignment of couplings etc.
(b) vibration frequency at half shaft speed or less; fit anti-whirl bearings.
TILTING PAD THRUST BEARINGS
Fig. 34 - Surface wiping of whitemetal-lined pad, in successive thin layers, due to excessive steady load at start-up.
Fit new pads. Improve lubrication at start-up, possibly by using jacking oil system. If possible reduce loading at start-up.
|Scoring Due to Foreign Matter or "Dirt"
|Damage Caused by Faulty Assembly
|Black Scab / Wire Wool Damage
|Pitting Due to Electrical Discharge
|Wiping of Bearing Surfaces
|Fretting Damage from Vibration
|Damage Due to Oveheating
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