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JuddJones

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Reply with quote  #16 
I will add one to your list. Incorrect keystock length on new motor installation. Always trying to do the best they could, our millwrights liked to install the new full length keystock. It didn't matter how many times we discussed sizing them appropriately. I began stealing the new ones when no one was looking so they had to install the old one that was the correct length.
Sledder2

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Reply with quote  #17 
Rusty,
Is this a vertical shaft motor? You mentioned it is a flange mount.

It seems like what is causing this condition is getting worse. Could it be a cracked shaft? I wonder what the shaft TIR was when it went in for the first repair and for the warranty fix?

fburgos

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Reply with quote  #18 
Quote:
Originally Posted by JuddJones
I will add one to your list. Incorrect keystock length on new motor installation. Always trying to do the best they could, our millwrights liked to install the new full length keystock. It didn't matter how many times we discussed sizing them appropriately. I began stealing the new ones when no one was looking so they had to install the old one that was the correct length.


[rofl]

Isnt there a balancing convention for key, in my old work we use to calculete the void and balancing with half "key"
OLi

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Reply with quote  #19 
Half key is the correct according to ISO but some do still have a sticker on the motor "balanced with full key" for historical reasons likely. I think the half key standard was introduced 40+ years ago so it's quite new.
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MarkL

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Reply with quote  #20 
Quote:
Originally Posted by JuddJones
I will add one to your list. Incorrect keystock length on new motor installation. Always trying to do the best they could, our millwrights liked to install the new full length keystock. It didn't matter how many times we discussed sizing them appropriately. I began stealing the new ones when no one was looking so they had to install the old one that was the correct length.


Judd, Thats like something I would do.

Sometimes 'Change management' of culture is a hard thing to do. 
RustyCas

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Reply with quote  #21 
Pete, the "report" shown was done recently after I suggested the motor be evaluated.  This motor ran fine for about 4-1/2 years and then a high 1X showed up.  They sent it out for repair (?) and when it came back the 1X was even higher than it had been.  They sent it back to the shop, when the "report" was then generated.
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newvibe

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Reply with quote  #22 
We had 2 large chiller motors (flange mounted, coupling, compressor gearbox) sent away for bearings replacement before.

When 1st one came back, 1x at the motor end was much higher than before repair. We asked the vendor to come in and check. The vendor agreed that 1x was high but say the rotor was balanced in the work shop, winding checked, laser aligned (cold and hot) etc. We insisted something need to be done as we paid a lot of money for the repair and we want it to be right. In the end, the vendor balance the rotor onsite by adding weight to the NDE of the motor. That brought the 1x down.

When the 2nd came back, after the cold alignment, all readings were good. But then after they carried out hot alignment, 1x at the motor end jumped up. Same again, the vendor agreed that 1x was high but say the rotor was balanced in the work shop, winding checked, laser aligned (cold and hot) etc. We insisted something need to be done as we paid a lot of money for the repair and we want it to be right. In the end, the vendor balance the rotor onsite by adding weight to the NDE of the motor. That brought the 1x down.
Wes

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Reply with quote  #23 
WOW, I can't wait to see the after install reading. any time there is a changing peak at 1X and no other data, shows something is deteriorating. (if there is no other changes going on either with the load or mounting). It is difficult to pick the actual frequency. Even changes to balance should simply jump to a new steady amplitude.
Going to watch this one play out.
RustyCas

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Reply with quote  #24 
Had a large chiller motor once (3600 rpm) that saw a steady increase in 1X vibration of the motor, but not the chiller.  I called this out as a "probable broken rotor bar, or bar loose at the end ring".  They sent the motor out to be refurbished.  Shop said they saw no evidence of imbalance.  Motor was reinstalled, and when I was next onsite I checked it.  It had been in normal operation a couple of weeks, and the vibration was the same as when I called it.  "I still think you have a rotor bar issue."  "Shop said it was OK."  "Well, it's your motor."  A couple of weeks later the rotor bar ended up in the windings.

A cold rotor can look quite normal when it's inspected, cold.  When then "refurbished" (cleaned, new bearings, heavy coat of paint on the outside) and run in the shop with no load, it may seem fine. But it may not be fine.

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OLi

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Reply with quote  #25 
This motor will fail shortly. It doesn't matter it is a rental........ Larger vacuum pump motor stops the papermachine until replaced, It did fail,, shortly.
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Danny Harvey

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Reply with quote  #26 
Rusty,

WRT the report, it looks like it was performed by someone who knows how to load a data collector, collect some data from a database that was built for their shop use, and print out enough graphs to call it a report. I doubt if it meant as much to them as it does to us (which is not really all that much).
RustyCas

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Reply with quote  #27 
They sent the motor back to the motor shop. Apparently they had put a new shaft in the rotor and it was “too big” (whatever that means), so they put another shaft in it. I checked it late Friday, and the vibration looked the same, except it was higher than before! I asked them to shut it down over the weekend so I could check it “cold” today. That didn’t happen. It’s off now and hopefully it will cool down by the end of my day here.
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Sledder2

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Reply with quote  #28 
If they manufactured a new shaft they might have missed a bearing shoulder measurement when they printed the shaft. That's what it sounds like to me if it's "too big".

Another thought :
Could it be the rotor fit to the shaft be loose? You should check out the old shaft and see if there are signs of fretting on the shaft from movement of the rotor stack. Maybe when the rotor heats up it loosens up and gives you an un-balance.
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