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Acceptable Clearance with Backup Ring

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bryansonnier

Mechanical
Dec 20, 2011
80
TLDR: Is there a standard or literature that covers what the limit is on clearance to seal WITH a backup ring.

Okay, so there is tons of literature about o-ring extrusion gap clearances and the durometer needed for each (could be parker did it and everyone copied but its widely published). In ALL and i mean !!ALL!! the literature they say "if you're extrusion gap is to the right of this curve then you need to use a backup ring". So okay i have a high torque 1 rpm application that i have to seal to 5000 psi. The torque is driven by a bevel gear and i have bronze bushings (CD955) to keep the rotating part inline. My current extrusion gap is a little on the high side but within standard o-ring tolerances however after only a couple thousand cycles the bushings have worn to the point where the rotating part is rubbing metal to metal at the area where the o-rings are (because of the close tolerance).

Here is the question: Is there a standard or literature of any sort (i'll even take disreputable at this point) that covers what the limit is on clearance to seal WITH a backup ring.

I would like to push my clearance which is currently 0.004" to about 0.010" to give more room for part wear and extend cycle life.
 
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