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marksl

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Hi Guys,

As the subject says I'm seeing a raised 3x running speed at both motor and Pump DE male locations in an axial direction only. Motor is coupled to a Busch AC100 Vacuum Pump. I have been monitoring this pump since 8/2014 and the amplitudes in the latest survey are higher than we have seen in the historical data. The 3x was also of concern in the previous survey and we inspected the coupling and found no usual wear.
Any ideas would be greatly appreciated

Thanks

Mark 
Edwin

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Hi,
Did you also check alignment? 3X axial can be generated in the coupling due to an angular misalignment.

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Noknroll

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I've also seen 3X axial in severe looseness, shaft worn in bearing mounting area
marksl

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Thanks guys, I've scheduled another inspection of the coupling and alignment check
marksl

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Ok we carried out another inspection today and didn't find anything to explain the high axial 3x running speed.

1. The alignment was spot on
2. Displacement on motor side 0.1mm, while on the pump side it was measured at 0.4mm (is this excessive for this type of pump)
3. There are 6 separate rubber elements some of the corresponding jaws were shiny compared to others but there was no excessive wear noted.
4. There was some "roughness" noted when rotated by hand at the pump. The timing gears are located at the coupling end of the pump.

Any further ideas also interested if anyone has seen a coupling like this before? P1020553.JPG 

Edwin

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Reply with quote  #6 

Also checked the coupling for enough axial float?
If all is fine with the coupling you could:
1. Find out if any machine part is related to this 3X  (what type of unit is thsi exactly? 3X can come from the process itself)
2. Look very closely if it is exactly 3X at all times
3. See what is the relation between different locations and directions for this component
4. Check if there is any abnormals in acceleration spectra. Especially 3000 to 4000 Hz

Good luck


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Dave Reynolds

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Reply with quote  #7 
markSI,

Did your vibration data change after inspecting the coupling? What method are you using for alignment? Did you check the set screws on the coupling hubs? Are the rubber inserts hard due to age and temperature?

Looking at the image you provided, the axial face of the rubber inserts, there are "shiny" spots, it appears to me that there is uneven axial contact on the rubber inserts. At top dead center of your image it looks like the round pin is making contact with the cast surface of the coupling?

Dave
Walt Strong

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Change the coupling elastomer element, and I bet the 3X vibration goes away.

Walt
Noknroll

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I agree with Dave Reynolds wear marks on front face of rubber elements look like parallel misalignment, 10 oclock has biggest contact patch, 12 oclock smaller contact patch and 2 oclock has nothing. 
what do you mean by displacement of 0.1mm and 0.4mm? is this correction movements horizontal or vertical? if so, 0.4mm for me would be considered as misaligned.
marksl

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Quote:
Originally Posted by Noknroll
I agree with Dave Reynolds wear marks on front face of rubber elements look like parallel misalignment, 10 oclock has biggest contact patch, 12 oclock smaller contact patch and 2 oclock has nothing. My technicians didn't think the wear on the elements was anything significant
what do you mean by displacement of 0.1mm and 0.4mm? is this correction movements horizontal or vertical? if so, 0.4mm for me would be considered as misaligned.
We did a lift test on both shafts and measured the displacement using the laser alignment equipment. At the pump this measured 0.4mm
marksl

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Reply with quote  #11 
Quote:
Originally Posted by Walt Strong
Change the coupling elastomer element, and I bet the 3X vibration goes away.

Walt


I'm still trying to identify the coupling as the marking on the hub weren't much help. We've managed to determine it's a KTR Poly of unknown size at this stage.
MarkL

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Reply with quote  #12 
Mark we aKtr agents have you shaft sizes? I might be able to look it up for you.
Noknroll

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Reply with quote  #13 
a lift check showing 0.4mm for me would be out of tolerance unless its something like a big mother 300mm shaft rolling element bearing
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