estimating sealing force

[Ivan Silva]

Folks, I've been surfacing on the internet trying to find any guide line on how to predict how much force is required to seal an device with o ring. The matters is I need to design a pneumatic cylinder to exert the desired amount of force to seal the device but everything I find until now is the force per linear inch data... Someone could gently help me?

 

[IRstuff]

?? multiply force/inch by circumference.

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[Ivan Silva]

You mean by the perimeter? I have been thinking about it. It's works just like an spring? Could I use the Hooke's Law

 

[3DDave]

What would you use Hooke's Law for in this case?

 

[Ivan Silva]

I don't know if it's right but by what IRstuff said and the unit of force per linear inch data range (pounds per inch)I've deduced that Hooke's Law could be used...

 

[3DDave]

It's like estimating how much the o-ring weighs based on the weight per linear inch, not on the deflection, which isn't mentioned. Makers of o-rings publish the required force to establish a seal for each cross-section on a per-linear-inch for each material, so the length * force-per-linear-inch gives the force required. The o-rings are compressed a fixed amount.

 

[desertfox]

Don’t know whether this might help

https://www.applerubber.com/hot-topics-for-engineers/forces-needed-to-compress-seals/

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[IRstuff]

I wouldn't have used circumference if I meant something else.

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[saplanti]

I think it depends on the hardness. The best is to test the o-ring in the groove until the flanges come to the face-to-face contact.
Some of the manufacturers can probably give you guidance about the force required.
In the large flanges with o-ring seal the sealing forces mainly ignored since it is to low against the tightening for pressure.

 

[hydtools]

Per Parker book use oring midline circumference multiplied by force per inch.

What irstuff said.

https://promo.parker.com/promotionsite/oring-ehandbook/us/ehome/ci.O–Ring-Compression-Force,EN.EN

Ted

 

[saplanti]

For preliminary estimate you can follow hydtool’s recommendation. However the Parker guide does not give how these graphs derived, in/out of grooves, with/without back-up rings. Elastomer o-rings can change their shape, fill the cavity they are in under pressure. There are large number of factors for the pressure loads which may effect the friction force.

In case you are designing one or two cylinders for special purpose the guide above is sufficient. If you are targeting to reduce or find the exact piston driving force required for large number production you need perhaps do the test, document it and convince yourself.