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RustyCas

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Reply with quote  #1 
I'm sure that many of you are familiar with this coupling.  I have a large customer that uses a ton of these on their water pumps.  Don't know the exact size, but it's the larger 2-piece element with the metal ring.

Something I see too often when a new element is installed is high 2X vibration due to the element being "pinched" between the hubs.  The installation manual states:
Quote:
Slide back the unfastened flange and install the sleeve. The sleeve should be seated against both flanges but not compressed.


I've always been of the opinion there should be some axial clearance between the hubs and the element because the element twists under load and (in my mind) expands the element axially. I'd like to give the mechanics an actual procedure for installing the elements but I'm not sure how much clearance to allow.  Do you think an 1/8" is sufficient?  I didn't measure the one I found pinched the other day, but it looked like the hub flanges overlapped the element flanges by a good 1/4-5/16".

Do any of you have direct experience with this?

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Danny Harvey

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Reply with quote  #2 
Rusty,

They specify hub spacing in the manual.

Most will use Type S flanges with the Type E Sleeve that you describe.  Type SC would be the type S flanges bolted to spacer hubs. Type J would be small cheap stuff. I'm not sure about Type B and C but you can look them up in a catalog if need be.


 
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RustyCas

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Quote:
  4. Position the flanges on the shafts to approximately achieve the G1 dimension shown in Table 1, with an equal length of shaft extending into each flange. Note: minimum shaft engagement is 0.85 * shaft diameter. Tighten set screw(s) of one flange to values in Table 2 using a torque wrench.

5. Slide back the unfastened flange and install the sleeve. The sleeve should be seated against both flanges but not compressed.


My reading of this says the G dimension is to get the shafts properly positioned within the hubs, and they are not allowing any axial clearance  I watched an installation video also and no clearance was allowed. This was by a distributor (?) so not sure it's accurate, but it's in line with the instructions above.


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Walt Strong

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Reply with quote  #4 
My thought is simply this: the coupling cannot transmit full torque unless the elastomer element teeth is fully engaged with the hub teeth. The manual specifies a G-dimension that causes the hubs to be snug, but not tight/compressed with the hubs. I have been working on gas compressors (300 hp 3590 rpm) with TB Woods Side-10 coupling. The compressor service technician left nearly 3/8" gap. I did not speak to him, but plant technician said that was his "practice" without technical reason! The coupling element had taken a permanent sheared shape that was contributing to unbalance and misalignment forces causing high vibrations. My recommendation is to follow the coupling OEM manual, unless you have a really-really good reason to deviate!

Walt
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