Hi,I need to find a suitable material for o-rings for my rocket.

[Aki]

Hi,

I need to find a suitable material for o-rings for my rocket. It will be used in the mounting of a stainless steel combustion chamber, so I need the o-ring to be able to withstand high temperature and pressure. Any suggestions?

Thanks

 

[Gokul43201]

Do you have numbers for the temperature & pressure?

 

[Q_Goest]

Hi Aki,
The pressure an O-ring is good for is dependant on something called the "extrusion gap". That's the gap between two parts on the low pressure side of the seal and into which the O-ring is forced (extruded) by the pressure. This gap distance is a function of the O-ring's hardness. The harder the material, the larger the extrusion gap can be. Here's a chart that gives that information: http://www.marcorubber.com/msg-fig6.htm
(They call extrusion gap the "clearance gap" on this web page. And the hardness of the O-ring increases as you go from 60 to 90 shore A.)

If pressure is too high, a backup ring can be used. I've not seen any good sources for this, but I've seen O-rings used up to extremely high pressure with backup rings or with essentially zero extrusion gap.

Regarding materials, Parker is debatably the leading O-ring manufacturer in the world. They have a material compatibility chart here:
http://www.parker.com/o-ring/fcg/fcg.asp

Parker also has a designer handbook available on the net here:
http://www.parker.com/o-ring/Literature/ORD5700.pdf

Visit their website for O-rings here:
http://www.parker.com/ead/cm2.asp?cmid=3106
(they make a vast variety of hydraulic and pneumatic equipment, so you may suddenly find yourself on a different division's web site.)

Take a look on the third line down (black first line, grey second line, white third line) where it has the headings:
O-ring
Products> Services> Literature> Markets> Applications>

And click on Literature which opens up a drop down menu. Each listing takes you to another web page with a bunch of different information on O-rings.

If you have specific questions, I'll try and answer them. As Gokul has suggested, you need to be specific. Pressure and temperature is needed, along with what fluid you're sealing, and if it's a static or dynamic application, a rough sketch of what you're trying to do would help. We might then be able to steer you toward a gland design that would fit your application.

 

[FredGarvin]

If it's in a rocket, it's going to be a static application I would assume. The only real question is it going to be a female or male gland or is it a face seal. If it's high temperature, Viton is most likely going to be your best bet. Q has already given you a wealth of o-ring information. Any designer or engineer should have a copy of that Parker reference. It is very informative. Give the pressure and temp numbers along with the geometry of the seal and we'll get you going.

 

[chemisttree]

Most exhaust gas temperatures are fairly hot... like glowing hot.
I don't think there are any Parker o-rings that would hold up to that for very long. A better application would be to redesign the gland design to accommodate a Flexitallic gasket that is filled with vermiculite that expands upon heating to provide a positive seal.

more info here...
http://www.beltpower.com/images/flexitallic/pdfs/LiteratureHot.pdf

 

[FredGarvin]

It all depends on where the o-ring is placed. The entire vehicle will not be at that temperature.