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# O-Ring Calculation

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## O-Ring Calculation

(OP)
Hy,
I'm using O-rings for the first time & my worry is that the bore diameter is very close to the ring OD, but the compression seems to be OK.
I'd appreciate if somebody with experience in those calculations can confirm if that is correct.

It's a piston type seal, 100 bar, NBR O-ring.
[/link]

ORing ID=Ø70 CS=4

stretch=2%
=> Groove Dia= ringID*(1+stretch)=70*1.02=71.4

compression=20%
0.5*(BoreDia-GrooveDia) = gland Height =ringCS*(1-compression)
=> BoreDia=77.8

GlandFill=75%
GlandCSArea*0.75=ringCSArea
=> GlandWidth=5.3

Thank you

(OP)

### RE: O-Ring Calculation

Looks right to me. Check your tolerances using same formulas, i.e. what is worst-case compression (or lack of it), and worst case gland fill. Are you sealing a fluid compatible with Nitrile, and/or do you expect any volume expansion due to temperature rise - these would be reasons to decrease the gland fill slightly.

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