O-Ring Calculation

[mirovyaneto]

Hi,
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.

O-Ring 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

 

[HPost]

There is specific 'O' ring housing dimensions and tolerances for both static and dynamic application all across the Internet.

http://www.parker.com/literature/ORD 5700 Parker_O-Ring_Handbook.pdf

For example

Have a look at this and see how the recommendations stack up against your figures.

HPost
CEng MIMechE

 

[Hidromar]

HI, mirovyaneto

You are right with your calculations.

Even the O-ring O.D. is pretty close to bore O.D. you avoid an excess of contact at this point. Doing this way, you avoid an early damage of the seal (more contact->more friction->more heat->more damage) Tests have been done showing that, ideally, a difference between 0% up to -2% raises best results on time (in this case).

Don't take care about this point because the O-Ring seal thanks to its automatic behave once compressed when installed on its housing.

http://www.hidromar.es