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fburgos

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Reply with quote  #16 
agree, 3:1 is very daring (or brave I dont have the right word with me) to suspect resonance,  for me is at least 6:1, I think text book sugest 10:1
Danny Harvey

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Reply with quote  #17 
I'm not sure if anyone pointed this out but if you suspect that it is resonance, the best of the five ways to correct it is to remove the exciting force. If it is believed to be misaligned, align it and you will remove the exciting force. You might want to carry the alignment beyond the tightest of standards to minimize the exciting force.

Imbalance is going to be harder to remove because it can only be corrected to a small degree with static adjustments and operation at or near the natural frequency of some component to balance it becomes difficult when signal amplification is occurring.

Depending on the signal amplification, by removing the exciting force, the natural frequency might not matter and instead of adding mass, stiffness, damping or a passive damper, you might fix it with just an hour of alignment.

Your amplitude is the velocity spectrum is not that bad but it looks more like imbalance to me too. Your enveloped spectrum has some things of interest, but I couldn't really say much about it other than those peaks COULD indicate some bearing issue. You need the bearing ID and the shaft speed to determine if it is a bearing defect. Then you need to look at the amplitude in the twf to determine the severity.

Anyway, my opinion is that you should try to remove the exciting forces and not worry about whether it is resonance or not.



Vibe-Rater

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Reply with quote  #18 
I agree with you Danny, best to remove driving force as best as possible. After that it often is down to structural stiffness coinciding with the remaining driving force.  It gets exciting then! - Excuse the pun. And a whole lot more complicated.  I detected a half times dryer cylinder speed condensate sloshing vibration which shook an entire floor on a paper machine once.  That was solved with several Million dollars and replacement of all siphon tubes converting them to stationary. T'was at Sinsk's mill well before he set foot there.  I also find that fan manufacturers are generally poor supporting frame designers.  They just give a pile of metal to a wleder and they go for it. Then selecting the wrong spring mounts which don't allow even weight distribution.  Oh well.  keeps us in a job. rgds
OLi

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Reply with quote  #19 
Most cost effective and long term stable solution if you suspect resonance and exiting force is speed dependent would be to change the speed, 10% may be enough and if the vibration peak before current operating speed you should increase and if you are not experiencing that peak you should lower the speed, if it is possible that is. You should balance and align to normal standards anyway. By the way, my rule of thumb to indicate a resonance requiring attention is a H/V reading factor of "more than 3". So higher than that special if V is higher as normally H is the higher would be a strong indication of resonance in my book.
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Ralph Stewart

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Reply with quote  #20 
Quote:
mikusp

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 #6 
 
what information is needed?


Hello mikusp,

Just wondering where you are? [smile]

Thanks and Have a Great Day,
Ralph

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RustyCas

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Reply with quote  #21 
Perhaps we should just pause our efforts to help someone who isn't checking in, and not taking the time to provide any information.  Must not be much of a problem.
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Curran919

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Reply with quote  #22 
Quote:
Originally Posted by RustyCas
Perhaps we should just pause our efforts to help someone who isn't checking in, and not taking the time to provide any information.  Must not be much of a problem.


I think it was clear from the first post that they weren't really looking for the analysis we would want to give.
Ralph Stewart

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Reply with quote  #23 
Quote:
RustyCas

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 #21 
 
Perhaps we should just pause our efforts to help someone who isn't checking in, and not taking the time to provide any information.  Must not be much of a problem.
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Curran919

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 #22 
 
Quote:
Originally Posted by RustyCas
Perhaps we should just pause our efforts to help someone who isn't checking in, and not taking the time to provide any information.  Must not be much of a problem.


I think it was clear from the first post that they weren't really looking for the analysis we would want to give.



You guys might be right, but it could be, since he described himself as "New diagnostic",  he was feeling a little bit intimidated by such an array of experience displayed within the few positive replies he received. [smile]

I hope he realizes that there is a very, very huge possibility that none of the members knows everything about everything, and some of us need to ask questions in order to get a better picture of what might be going on, before we say very much about the original posting's question(s). [confused]

Just my opinion and I could be totally wrong.

Thanks and Have a Safe and Great Day,
Ralph

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Danny Harvey

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Reply with quote  #24 
I suspect that Ralph is right.

We may have overwhelmed him with questions he didn't have the answers to.

If he comes back, we can probably help him get the answer he needs.
fburgos

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Reply with quote  #25 

I think a common misconception for the rookie in vibration (and managers) is that a one spectrum gives you enough information for diagnostics, and this idea is often encouraged by seller.

He might felt overwhelmed or just he is just busy, I hope he come back with feedback

MarkL

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Reply with quote  #26 
Hopefully, isn't the last we see of the guy but it happens and was always something I hated in the old site, I would find a great question or article..and no response...or worse a few decent comments and then the OP doesn't bother responding or feeding back information and the thread died, always smacked of 'they got a vague answer and ran with it' Probably using it in theyre diagnosis????? As Ferdy says, There are far too many nuances in diagnosing a fault, not just single spectra and some lacklustre details on the machine.







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