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JKozlo

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Reply with quote  #16 
The last recorded clearances I've been able to find for this bearing were 0.0146" in the vertical and 0.0184" in the horizontal, shaft diameter averaging 10.9986".
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John from PA

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Reply with quote  #17 
Quote:
Originally Posted by JKozlo
The last recorded clearances I've been able to find for this bearing were 0.0146" in the vertical and 0.0184" in the horizontal, shaft diameter averaging 10.9986".


Reasonable for an 11 inch (nominal) shaft.  All the more reason to get that System 1 set up to acquire shutdown data.  You can get a feel for shaft position within the bearing clearance.
George D

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Reply with quote  #18 
My concern would be less for the shaft vibration and more for the elevated casing values.  If you choose to accept ISO 10816-7, shaft vibration up to 50% of the internal diametral clearance is acceptable for unrestricted long-term operation.  That would be about 7 mils p-p in your case... which you are well within.  I agree with John, and would be interested in seeing the transient data?  Data from your last coastdown may be available in your System1 archive?  Recommend that you make sure to select all data sources... trend, alarm, and transient if data was stored and hasn't rolled off yet?  That may help validate whether you are riding close to a critical that may be reflected in casing vibration?

I noticed that you did not specify whether the velocity data was RMS, or Peak?  A friend uses an Entek box, and explained that one of the options for display is "true-peak", which, I believe, would pull the absolute highest peak off the time-domain and represent that as the velocity reading.  Other Entek users, please verify?  I think many of us use either RMS, or "derived peak" which is a calculated peak from each bin of the spectra.  I'm not going to champion whether that is right or wrong, good or bad... only recommend that you verify the units you are looking at?  I believe true-peak may display a higher value than would otherwise be expected from a derived peak or RMS.

If you have 0.45 ips velocity, that's kinda high?  Further changes may represent a change in the integrity of the structural support?



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