Bearing spalling 1

[nawlins]

Maintenance man has a double row spherical roller bearing. Inner race bore is 9" The inner race looks to be in good shape but the outer race has heavy spalling about a quarter of the way around it's inner circumference. The cage is 2 pieces and is made of Al. One of the cages has a crack right through in about the middle of where the roller ends touch it. I guess it is called the pocket. My question is would this be too much axial loads? If it is why wouldn't both races have spalling? Thanks Mates.

 

[MikeHalloran]

Have you tried reverse-engineering the bearing against whatever loads you can measure or estimate?




Mike Halloran
Pembroke Pines, FL, USA

 

[Tmoose]

Have you looked at the various bearing failure analysis documents available on line ? Most every bearing manufacturer has at least one.

This is one of my favorites -

http://www.pheltom.pl/katalogi/FAG uszkodzenia lozysk.pdf

Cage damage (wear) is often a result of poor lubrication.
Busted cages can result from misaligned running.
Localized race damage can result from poor bearing housing geometry.

Spalling is can be the natural end-of-life failure. How long was the bearing in service.

 

[electricpete]

Busted cages can result from misaligned running.

Does that apply to spherical roller bearings? (I wouldn't think so)

. One of the cages has a crack right through in about the middle of where the roller ends touch it.

So if I read that right, the cage was still doing it's job to control the position of the rolling elements. In that case IF we assume the two symptoms are related (not necessarily a good assumption), the spalling may have increased stress on the cage.

Got any pictures. ?


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(2B)+(2B)' ?

 

[Tmoose]

Hi Epete, I hope you are doing well.

Yeah, despite what Sam used to say, spherical rollers can self align to compensate nicely for a degree or so of static misalignment, like results when the bearing pedestals are of different heights (as they always are) or if a uniform shaft carrying a fat center hung impeller bows to a consistent sway backed state in operation.

http://www.skf.com/binary/30-143712/1011%200024%20-%2010000_tcm_12-143712.png

or page 4 here -

http://www.skf.com/binary/21-148465/6100_EN.pdf

But sometimes the shaft abutment shoulders are not machined square on the shaft, or the tapered adapter is jammed kind of like this -

https://cdn.flii.by/image/ok886sbrd64.jpg,

That creates dynamic misalignment as is discussed a little on page 35 in the SKF link.

http://www.skf.com/binary/21-148465/6100_EN.pdf

Then the inner race moves back and forth axially like a swash plate, and the rollers have to weave back and forth across the outer race which involves some sliding, which the cages try to control.

Also page 125 (127?) here -

http://www.skf.com/binary/tcm:12-114679/140-710 BIMG 11_2012_tcm_12-114679.pdf

Until the OP posts a useful amount of background info the discussion will remain mighty ethereal.

Maybe next time.

 

[electricpete]

Hi Dan! Thanks for the response. Good point about dynamic misalignment.
I liked your photo of jammed tapered adapter although it may have been a little over my head.

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(2B)+(2B)' ?

 

[nawlins]

I have looked online at the resources available. Nothing is cast in stone so to speak. Too many things can be caused by too many variables. Like what came first the chicken or the egg.

 

[Tmoose]

" Too many things can be caused by too many variables. "

Careful assembly of the history, etc , plus confirmation of shaft and housing geometry, and thorough evaluation of the bearing just as it was removed including wear debris and old lubrication , and evaluation of operating conditions and resulting loading can often whittle away nearly all the variables.

Anything less is, well, less.

If the bearing did not attain a reasonable life, the root cause really needs to be sought out if better performance is desired.

If someone is just curious, but not so curious as to make the effort to root out the facts, then that's OK too.