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weller

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Reply with quote  #1 

Found a motor that has evidence of fluting in the vibration spectrum.
Has anyone had success at finding fluting with ultrasound? And if so, was it through contact or non contact? Also what  does the sound resemble?


Walt Strong

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Reply with quote  #2 
Yes with contact sensor. It should produce a high dB value and sound like a Buzz. May require firm press of sensor onto surface if high vibrations are present.

Walt
weller

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Reply with quote  #3 
 Thanks for the reply. Here are the sound files from the ultrasound meter. Any thoughts?

 
Attached Files
wav drive end.wav (45.04 KB, 27 views)
wav opposite drive end fluting.wav (45.04 KB, 23 views)

Danny Harvey

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Reply with quote  #4 
Can you measure for shaft current and voltage?

It sounds like fluting to me but that's a pretty subjective opinion. 

I have always been amazed at how long bearings will run with fluting. It is usually so loud that it gets everyone's attention right away.
MarkL

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Reply with quote  #5 
What meter are you using Weller?
I’ve a lot of dryer fans in milk powder factories that suffer with this.
Normally see the haystack in acceleration around 180kcpm
OLi

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Reply with quote  #6 
In some cases they don't live that long. I think the shortest cycle time I have seen is like 3 weeks, every time. I normally say that VFD caused fluting is the fastest way to destroy a bearing I have seen and that is a indication by itself, if indications pop up after a few hours after replacement, then you know.
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Walt Strong

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Reply with quote  #7 
You can put a Yellow Machine Condition Flag on Any machine with a VFD variable speed control without any measurements, because of these potential faults or fault conditions:
  1. Resonant lateral vibrations (amplifies unbalance and shaft misalignment)
  2. Resonant torsional vibrations (shaft cracks and coupling failure)
  3. Resonant pulsations (pumps)
  4. Motor overheating (poor cooling at low speed)
  5. Bearing and gear faults from stray current (Fluting)
  6. Electrical failure (VFD circuit components)
  7. Environmental Noise (community complaints)
  8. Environmental Vibrations (see resonant vibrations)
 
Did I forget anything?
 
Walt
 
weller

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Reply with quote  #8 
The ultrasonic meter used was a STD 270. This motor is not controlled by VFD but does have a soft starter . Definitely need to look further.
Walt Strong

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Reply with quote  #9 
"STD 270" I think you mean SDT!![biggrin]

Walt
weller

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Reply with quote  #10 
Yikes... you're right, Freudian slip..... i think.
weller

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Reply with quote  #11 
Interestingly enough the prints show the motor wired with a soft-starter, but that was changed later to VFD. Thank you for all the responses.
ruben

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Reply with quote  #12 
I have the SDT 270 and I´ve never used for fluting detection, but it´s relatively easy to detect by mechanical vibration:

Source: Usually Motor fed by VFD. 

Symptoms:
low frecuency: 1xBpfo till 3xbpfo more or less. I´ve seen that it´s common to find the first harmonic of line frecuency 1xLf even you are feeding with other electric frecuency (50Hz or 60 Hz). Harmonics of line frecuency also may appear.
High frecuency: 1xBpfo and a lot of harmonics.
fluting 1.jpg 
Why mainly Bpfo?? because it´s the best way for parasitic currents to get into the rotor from the stator (see the way in next photo).
fluting 2.jpg 

Consequences:
outer race "fluting" and rollings or balls opaque grey.
fluting 3.jpg 
Solutions:
1. Adjust Switching Frequency in the AFD to the lower possible Value.
2. Bearing and bearing house
3. Electrical motors till 100Hp to fit discharge ring rubbing against the shaft.
4. Electrical motors over 100Hp to fit discharge ring rubbing against the shaft on drive end plus isolated bearings over all on opposite motor drive end (free side).
5. Good mass connection between motor and earth.
6. Measure vibration before and after apply solutions in order to verify good job.



electricpete

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Reply with quote  #13 
Quote:
I´ve seen that it´s common to find the first harmonic of line frecuency 1xLf even you are feeding with other electric frecuency (50Hz or 60 Hz)

Do you (or anyone) consider this:
  1. an indication that fluting is occurring, or...
  2. an indication of drive malfunction, or...
  3. a somewhat normal/expected indication expected for some motors on vfd? 


OLi

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Reply with quote  #14 
2. Unless the VFD is set to the same as 1xLf only my experience and could be totally wrong
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ruben

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Reply with quote  #15 
.[CITA = OLi] 2. A menos que el VFD esté configurado como el 1xLf solo mi experiencia y podría estar totalmente equivocado [/ QUOTE]


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