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VibGuy~5

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Reply with quote  #1 
We took an oil sample from one of our centrifuges last week. The oil is food grade, so went in clear. After 2 months it came out black.
Oil analysis results came back with high concentrations of copper and zinc, in other words, brass.
Straight away I'm thinking cage defect and possible shaft lock of an 800 Kg bowl spinning at 6000 RPM.
Am I being too cautious? Anybody got any horror stories of centrifuge shaft lock?
I'll be able to take readings on it tomorrow.
OLi

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Reply with quote  #2 
If it is a vertical thing with a brand from around here some have a very special neck bearing mount that may reduce bearing fault signal path to the exterior, just so you know.
Maybe take a IR camera shot and compare with another? Sound one way or another should also be a possibility.
I only collected stories from botched balancing efforts on those machines where weights of considerable size was mounted in ways you don't believe and only rarely resulting in bowls spinning off in some undefined direction...... So be careful.
Only impressive things I recall was a condensate pump in my youth that I reported for alignment the day before and in the morning the 150mm diam shaft was bent 90 deg and the coupling was a bit further down and it was a bit black all around. Other one was a brake on a oh crane where the shaft in the gbx broke a steel melt went down and brake disc went thru the roof and ended on the tracks outside the railway station half a block away.

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VibGuy~5

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Reply with quote  #3 
The big question is if the bowl does spin off in some undefined direction, is the cover strong enough to contain it? Have they done their FEA impact analysis?
The brand is from a larger country to the South of you (it is vertical)

OLi

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Reply with quote  #4 
Oh it's the "other" brand, don't know about their neck design but they likely did some calculations at least.....
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MarkL

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Reply with quote  #5 
I’ve done some vibe work on those also and wondered if the same what’s the failure mode if they do fail.

They always run with a certain degree of unbalance either the vertical or horizontal variant, the vertical types come in either a belt drive or a worm gear type, seen brass gearing in the latter of one, was the Swedish variety I believe.
VibGuy~5

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Reply with quote  #6 
This one is a flat belt drive, motor and bowl vertically mounted. All stainless, so IR not much use and the bearings are buried anyway. Not that there would be much heat from a developing cage defect. I'll have a listen ultrasonically to a good one tomorrow

OLi

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Reply with quote  #7 
Maybe as a final old time test, compare current consumption when empty?
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Dan Timberlake

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Reply with quote  #8 
"After 2 months it came out black...."

I would be mighty suspicious.

Do they always to that?
VibGuy~5

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Reply with quote  #9 
No. Not at all. Turns out it was the cage. We caught it just in time.
Very happy to see predictions come true. Who isn't??[smile][smile]
VibGuy~5

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Reply with quote  #10 
20181203_143107.jpg  20181205_133115.jpg 

6000 RPM. 800 Kg axial load. Were we lucky?

OLi

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Reply with quote  #11 
Yes [smile] the luck that comes from experience? Was the sound like a disaster waiting to happen [rolleyes]?
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MarkL

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Reply with quote  #12 
Wow, that was a good catch.
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