Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Cryogenic Sealing

Cryogenic Sealing

Cryogenic Sealing

I need some help/advice on the methods used in cryogenic sealing.  I am in the process of designing a cryogenic connector (40 bar) for use with liquid oxygen, nitrogen and argon, and need some advice on the best sealing interface to use.  My all brass connector has a 'nut' on a series of ball bearings being pulled up on a flange via a special spanner.  At present i have used an equilateral triangle cross section virgin ptfe seal clamped between two taper's which works ok at ambient but leaks at cryogenic - when the seal gets cold!! What other cross sections are used in cryogenic sealing to better allow for the shrinkage and are there any other materials i can use?  Are there standard seals out there that i can incorporate into my design?

RE: Cryogenic Sealing

I take it you're refering to some kind of piping connection, ie: tube to tube or pipe to pipe joint?  Or are your refering to something else?  I'm confused by the part about ball bearings.  How large is the connector?

It sounds like you're using a triangular Teflon gasket, probably inside a gland, similar to an O-ring gland.  Is this correct?  If so, I'd suggest using a copper gasket.  Anneal it first.  Ensure contact stress is on the order of 10,000 - 15,000 psi so that the copper gasket deforms when installed.  That's just a rough number, something well above the 6000 psi yield strength of annealed copper.  You'll have to calculate pressure loads and bolt forces of course.  The contact width should be about 0.030" to 0.050", and be tapered so it's only that thin right where it makes contact with the flanges, but gets thicker behind this contact face.

Another option is to use a spring loaded Teflon U-cup seal.

If it's pipe, you can use pipe threads.

For tubing, most tube fittings are acceptable, ie: Swagelok, Parker, Flared fittings, etc...  

Hope that helps.  Perhaps a bit more info would help me to understand what you're doing.


Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close