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MarkL

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I do work on some Piller MVR  blowers/fan and recently was informed that the fan bearings are not basic rolling element bearing setups as I initially thought, they are fitted with a Hybrid fluid film rolling element bearing I had never heard of before 'SQUEEZE OIL DAMPER BEARING' See images attached.
Squeezeoil2.jpg  squeezeoil3.jpg 
 
 

Image result for SQUEEZE OIL DAMPER BEARING squeezeoilbearing.jpg 

Has anyone come across them and how do you monitor them? I take readings on both units for over 2 years now and they run as smooth as a sewing machine.
Last Friday the OEM tech was onsite at one of them and comment that the displacement probe they fit was in alarm(about to go to shutdown level) but the velocity and acceleration system we have fitted wasn't showing anything of concern. The system fitted is using a 4-20 ma micron level trending displacement system.

Many thanks, guys.


John from PA

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You may wish to review the "Notes" on the concept at https://rotorlab.tamu.edu/me626/Notes_pdf/Notes13%20Squeeze%20Film%20Dampers.pdf

I have encountered the design on numerous occasions and actually designed squeeze film damper of sorts into a machine as a quick temporary solution.

A squeeze film damper is a method to introduce damping into the system. In fluid film bearings this is often accomplished by o-rings in the outside diameter of the bearings, or actually mounting the bearings in a clearance on the outside diameter that is filled with oil. In the case of rolling element bearings, since it is difficult to machine the OD of the outer race, often o-ring grooves are machined in the housing bore, and the bore is sized so that the bearing actually rides on the o-rings.  This approach is not to be taken lightly, some analysis should be done prior to proceeding unless this is something that is easy to accomplish and reversible.

For example, many years ago I worked on a gearbox designed by a consultant, not a typical gearbox manufacturer. The machine operated at 15000 RPM (+/-) and the pinion was quite violent passing through a critical speed. Because I could get o-ring grooves machined into the bearing cartridge in a few hours and this was reversible (a simple replacement cartridge could be made) we went ahead with modification without doing any analysis. This was a small bearing, probably a couple of inches on the OD. We machined two o-ring grooves, one at each end of the bearing and provided about 5 mils compression of the o-rings. The bore was oversize by a few mils with respect to the bearing OD.  This enabled the machine to run quite well, although long term another solution was desirable. Actually this company, which tested aircraft engines, used this temporary fix for about six months. Ultimately the gearbox was replaced with one that had fluid film bearings (and manufactured by my former employer, who knew what they were doing, unlike the consultant).
OLi

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Reply with quote  #3 

I have only seen this term on turbine bearings where they are used to cure bearing instability so that is another story.
I have customers in hydropower that think they can monitor bearing clearance in hydro turbines by only looking at
peak value from a eddy probe using the original corroded and rough iron shaft. I repeatedly tell them it is not so easy
and they don't like to pay for a system that get closer to doing that and they repeatedly get surprised that the data is a few times higher
than the physical clearance measured.
So as I guess you know, if the supplier knows the things it may be a good indicator as they use it, would it then be that the bearing that is worn
out of tolerance? Or the usual, scratched shaft, electrical etc. If bearing is just worn there may be no bearing condition data since there are no damage?
I guess the damper oil film would reduce the signal from the bearing so it is a problem with normal monitoring.
There used to be systems for slow speed bearings where you measured with the eddy probe against the ball bearing outer ring when mounted
and then from the eddy probe detected any hi frequency ringing from the outer ring that indicated bearing damage. I still try to find a case
where I could apply and test that. Just to use a eddy probe on a ball bearing that would be fun.

 

 


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electricpete

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I understand why someone might loosely call it  “Hybrid fluid film rolling element bearing”.  However I just wanted to point out that it carries none of the characteristics of a sliding fluid film bearing since the outer ring cannot rotate to develop a hydrodynamic oil wedge (anti-rotation pin).  But it is a rolling bearing with damping added (squeeze film damping as you said).  Sorry if I’m stating the obvious.  I have zero experience with any beast like that. 

MarkL

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Thanks for the information John. I read on the DNA makers site the reasons where to avoid the critical as you mentioned and seemingly these units work at they're optimum around 3500-3800rpm.

OLi you have me thinking, there's a locating pin at the vertical of bearing, unsure if its contact with bearing housing is loose or relatively stiff, might test it this morning and see if I get any useful data from it.

Pete
Ron Stiemsma

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Reply with quote  #6 
What is the displacement probe looking at?  If it is the journal movement is it there to ensure the machine has not lost the anti-rotation pin function.  I have never worked on one of these so I am just guessing. 
OLi

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Reply with quote  #7 
I just got  a old case revived with pretension bearings and a sort of grinder and it seems that in a similar way it is not a explicit bearing damage that give problems in operation but the wear of the bearings that generate to hi bearing clearance. So maybe we should be looking at the noise level and maybe in both cases a lowering of the noise as the bearing clearance increase since we maybe can't wait until the normal speed multiples pop up. I may have a chance to test the theory in April when they build a new machine set for testing. In your case it may be a good idea as you described to measure close to the locking pin and see if there are any data to be found.
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