Bearing landing deterioration

[behar]

Hi!
we have a fractionator bottoms between bearing pump whose service temperature 750 deg F, anti friction bearings have lube mist lubrication,the shaft is of 416SS material, we noticed on the shaft at the area under the bearing seat of both the IB & OB appears to have some kind of "attack", similiar to corrosion.Can anyone offer possible causes for this?

 

[sprintcar]

Rolling element bearings are high grade carbon steel while the shaft is stainless steel. Given electric current potential of the driver (motor) or other local sources, you may have galvanic corrosion.

"If A equals success, then the formula is: A = X + Y + Z, X is work. Y is play. Z is keep your mouth shut."
-- by Albert Einstein

 

[jet1749]

Difficult to diagnose without a picture, maybe fretting corrosion due to loose fit of bearings?

 

[JJPellin]

There may also be fretting corrosion because of a loose fit between the bearing and shaft. It might also be possible that the oil mist is contributing to the problem. This mist is carried in with air. So you are continually introducing oxygen to the bearing housing. If any moisture is present or if there is a galvanic reaction taking place, the mist is feeding it oxygen.

 

[Artisi]

I seen to recall (vaguely) a comment once that an environment devoid of oxygen can be very corrosive to S.S. A bearing housing at this temp. completely filled with oil mist could well be lacking oxygen.
Just a thought and maybe a good posting in the materials / corrosion forum.

Naresuan University
Phitsanulok
Thailand

 

[sairaj]

It may be corrossion or false mishandling in prior maintenance jobs,The condition monitoring people will usually check the vibration causes and abnormalities before dismantling the equipments and it may reveal the causes behind the deterioration

Regards
sairaj

 

[electricpete]

Without a picture it's anyone's guess. (even with would still be tough). I tend to agree with jet about fretting. Check the shaft fits.

=====================================
Eng-tips forums: The best place on the web for engineering discussions.