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Danny Harvey

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The attached photo is the load zone of the outer race of a Timken/Torrington 22244 K YM W33 C3 bearing that was on the head pulley of the boom conveyor on a stacker/reclaimer.  We know we had contamination with water and coal dust and thus corrosion etching in the outer race but this groovy pattern has me shaking my head.

You can actually feel these grooves in this wavy pattern that is seen in the photo.  There is some serious etching and it appear that this roll sat for a while because there are some rollers that have that etched axial pattern that looks like they sat in mild sulfuric acid for a while which is probably what they did.  They had this equipment down for an extensive rebuild and it may have sat in one position long enough for the rollers to get etched.

But the wavy pattern is something I've never seen in a bearing.  I've seen it in things like the wear ring of vertical roller mills but never a bearing.

We also know that the pulley exceeds the specified runout of .015" tir but I don't know by how much.

I plan to place a flexible tape measurer on the outer race, mark off 10" and count the number of waves.  Then I'll play around with bearing geometry and see if I can figure out what this twf means.

Any suggestions?

...well it looks like you can't edit a typo in the title so this is now a grooby bearing.

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jpeg groovy bearing.jpg (44.51 KB, 35 views)

Noknroll

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Reply with quote  #2 
Well to kick off suggestions......and a stab in the dark.......maybe 2 instances of false brinneling? Like ran after once brinnelled then ran and parked in a slightly different rolling element position and false brinnelled again.
JuddJones

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Reply with quote  #3 
First thing I thought of as well. Either sat for a looooong time in a high vibration area and this is false brinelling, or your corrosion theory. Wouldn't there be more rust in the worn areas if that were the case? In the photo the "grooby" areas look polished in the race on the right.
Sinski

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Reply with quote  #4 
A thought I had would be some sort of condition where the rollers were maybe stop/starting through the load zone and are maybe intermittently skidding. I do not know what would cause that as its just a thought. What lubricant is used and what condition was it in if known?
Curran919

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Reply with quote  #5 
Quote:
Originally Posted by Noknroll
Well to kick off suggestions......and a stab in the dark.......maybe 2 instances of false brinneling? Like ran after once brinnelled then ran and parked in a slightly different rolling element position and false brinnelled again.


From my gut, it looks like the grooves have a much higher pitch than just twice the ball pitch. It would be too perfect to have the angle line up 3-4 times to give such perfectly spaced grooves. With false brinneling, how much do you see the grooves weaken as you go out of the load zone?
Danny Harvey

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Reply with quote  #6 
Nok,

Two instances of false brinelling is possible but I would consider two or more instances of etching more likely.  The outage was something like two months which I don't consider long enough to have created false brinelling like Big J alluded to. In addition, the during the outage, everything on the Stacker/Reclaimer was down so I don't thing there would have been sufficient ambient vibrations.

Big J,

The grease was badly contaminated with coal and water so any traces of rust were possibly polished away by the sulfuric acid and dirt.

Sinski,

Skidding is another possibility. I'm wondering if it could be caused by loading and unloading of the bearing due to the pulley eccentricity.  I have asked for the measurements but haven't gotten them yet.

Curran,

Wouldn't there by definition be a hardening at the brinelled areas? Or are you talking about the areas immediately adjacent to the dents?


I'm hoping to try to figure out what it all means in the next couple of days but I'm not sure I'll have time.  So far I have measured 21 waves in 11 inches of outer race, I know the bearing geometry and know that the shaft turns 107 rpm.  It's a starting point.

Walt Strong

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Reply with quote  #7 
Is it possible to have electrical static discharge through the bearing? I recognize that the pattern does not fit the classic bearing ESD. I also don't know whether these types of belts typically have any form of grounding brushes.

A quick search indicates a possibility of ESD: coal belt conveyor static electricity
https://www.bing.com/search?q=coal+belt+conveyor+static+electricity&form=EDGTCT&qs=PF&cvid=503de421c10e4b479ca8bdfe88c6b1e0&cc=US&setlang=en-US&elv=AY3%21uAY7tbNNZGZ2yiGNjfNLd9SRHRk5UeAkc1jeL**MunnKTLGJUGa0Wx1os5ZASSASKG%21JJoXdItY2lBYqywabHk7EKp5UYd8oFnbpeydZ

Walt
Danny Harvey

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Reply with quote  #8 
Walt,

They have some sort of grounding in place but that doesn't mean that it's not the case.  These folks are exceptionally good at taking care of their stuff, though.

I doesn't have the machined appearance of traditional fluting but I suppose it could have been polished by the lube just like I described above.

It's on the list of things to check out.

Thanks to all
Rang

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Reply with quote  #9 
That very much looks like "scalloping" caused by smearing or skidding, which in turn could be from excessive Radial Internal Clearance (RIC) during bearing installation or an out or round housing. I've seen this on slow speed pulley bearings during factory acceptance testing. You'll see it in Peakvue data and hear it in your listening device. Autocorrelation can help by looking at the correlation factor.

EDIT: SKF refer to this as "roller shuttle" or "roller correction", others call it "skew". An article talks about metal to metal contact occurring, inducing "orthogonal sheer stress".

So if you do see or hear similar things during commissioning or base-line....well there's a place to start.
Curran919

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Reply with quote  #10 
Quote:
Originally Posted by Danny Harvey

Curran,

Wouldn't there by definition be a hardening at the brinelled areas? Or are you talking about the areas immediately adjacent to the dents?



Sorry, badly phrased. It doesn't matter now, but I meant:

I would expect the brinelled areas to be 'deepest' in the load zone and then to be 'shallower' at the opposite end. On the contrary, the groobiness appears to be the same around the circumference.
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