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marksl

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Reply with quote  #1 
I'm wondering how many others have had the situation where you just know there is a problem with a machine (strange noises, high temperatures etc) but the VA shows nothing noteworthy !!!!!
Danny Harvey

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Reply with quote  #2 
Yes, but there has almost always been a reason such as improper collection, bearings missing cages, etc.

It's up to us to figure out why nothing shows in our data and alter the way we collect and analyze it to suit the particular situation.

It's made more challenging if you are a consultant because follow-up data is more difficult to come by. That makes it much more important that the perceived problems are resolved at data collection.

It's not easy and I don't claim to do this every time. I share in the frustration.

But we always try to collect additional data when we perceive a problem that doesn't show in our route set-up.  I would like a two-way note system where notes like that could be passed between analysts and data collector but with CSI 2130 and AMS it's only a one-way system.

JuddJones

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Reply with quote  #3 
My biggest frustration is our continuous monitoring equipment (IFM), and my route based data collector (Enpac2500) rarely agree. I tend to trust the Enpac more, but it sucks taking readings on something with a handheld that is wired with 8 channels already.
OLi

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Reply with quote  #4 
If there are no balls left in the bearing you get no bearing inddicaion... been there done that.
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Shurafa

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Reply with quote  #5 
Quote:
Originally Posted by marksl
I'm wondering how many others have had the situation where you just know there is a problem with a machine (strange noises, high temperatures etc) but the VA shows nothing noteworthy !!!!!


I guess not all problems and/or failure modes are detectable by vibration data collection. Some detectable failure modes are missed because data is not measured in the correct "way".

When you put your hands on the machine, do you "feel" the vibration is really low and constant?

If, in your specific case, you hear an abnormal noise and can feel high temperatures, use ultrasound and thermography, if you can. Also, take vibration data using different configurations.

Why not share more details?

Regards- Ali M. Al-Shurafa
Beatnik

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Reply with quote  #6 
Quote:
Originally Posted by marksl
I'm wondering how many others have had the situation where you just know there is a problem with a machine (strange noises, high temperatures etc) but the VA shows nothing noteworthy !!!!!


It happens to me on fluid drives. There is no good ways for the vibration to travel between collection points and the bearings.

But really all I care about is the reliability and once I can hear a fault I call it and the replacement is made before failure.

I have a couple of frustrating cases. A vacuum pump that is very loud and the vibrations increased a lot but I have no idea what the problem is. All the frequencies increased (big noise floor and all the harmonics usually there are higher)). No sure if it's the timing, looseness creating contact between the lobes or something else. An expert will come soon and open it.

I have a gearbox that I hate, I got it replaced and repaired 3 times immediately after installation (over 5 years because each time they sent it to repair and then it stays a while in the warehouse) and it still knock at low speed shaft frequencies. Now that I realized it I'll make sure they replace the low speed gear next time but it brings me to my frustration #1: Not being able to have any contacts with the people rebuilding our equipements. So they have no idea why they receive the  gearbox, pulley or pump and I have no idea if my call was good and what work has been done.





Walt Strong

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Reply with quote  #7 
If "contact between the lobes" actually occurs, then the Expert won't get there fast enough! Perhaps something else is the cause of vibrations. What are the machine and vibration/sound details?

Walt
Beatnik

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Reply with quote  #8 
Quote:
Originally Posted by Walt Strong
If "contact between the lobes" actually occurs, then the Expert won't get there fast enough! Perhaps something else is the cause of vibrations. What are the machine and vibration/sound details?

Walt


I locked the pump, it cannot be used. We had one that exploded a couple of years ago and almost killed people and they are able to produce with the others so no one questioned my choice to shut it down.

One of my problem is that my online monitoring program is down so I can only compare to old data I took manually last year. Also since I almost never used this route, it's poorly programmed, it's the route created by MHM.  

I attached some spectrums and the pump manual. Mine is a horizontal one so the plan is at page 27. they are 2 lobes kind. The noise is not regular and not modulated, it does'nt sound like a bad bearing or a bad gear but I guess it could be the looseness created by wear on the gears or bearing...

 
Attached Files
docx PV7-6.docx (157.43 KB, 16 views)
pdf roots.pdf (4.46 MB, 39 views)

Danny Harvey

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Reply with quote  #9 
My experience is that these are prone to material buildup on the lobes which closes the clearance and causes the 2 x ts impacting.

Wear in the timing gears is also a possibility.
Beatnik

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Reply with quote  #10 
Thank you Danny. We'll open it with the OEM guy next week, if we are not on strike by then, I'll post the results.
Danny Harvey

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Reply with quote  #11 
I hope to hear from you soon and not by seeing your resume here!
RickP330

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Reply with quote  #12 
I have a machine I was sure I would find something, but according to VA it is as smooth as a mouse.  It almost sounds like cavitation by ear, but it's clear it is non periodic.  So I thought the FFT wiped it out.  But I don't see anything in the time waveform either.  Not sure what to make of this motor yet...
RP
Walt Strong

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Reply with quote  #13 
Cavitation typically appears in the vibration spectrum between 1000 and 5000 Hz, and is best seen with acceleration units. Typically eight or more spectral averages are needed to see a mound of energy, not a discrete peak, in the spectrum. Cavitation appears as sharp peaks in the time waveform that occur randomly. If you can hear the sound (like stones passing through the pump) of cavitation, then it should be measurable with vibration with the appropriate measurement point, accelerometer mounting and instrument settings. A lot of topics fall into the Frustration category, but you should really start a new topic for this discussion.

Walt
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