metal to metal joint seal

[jeffreyperria]

hey, i was wondering if anyone could help with a project i have been working on for a couple of weeks. here it is. i need a aluminum metal to metal zero or no leak joint. that will with stand a small molecule like r-134a. i would like to wring those two connections together without a gasket or o-ring. Would i looking at a situation like a gauge block surface, or would i have to go less rough.

if you could point me in the right direction i would greatly appreciate it

 

[patprimmer]

Have you tried the google feature on the site.

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[jeffreyperria]

yes i have been doing a google search for about two weeks now. basically i am wondering if any one here has any knowledge of wringing and the wringability of specific materials like aluminum

 

[dgallup]

Zero is a pretty small number. What pressure are you sealing? Typical lapped surfaces on a fuel injector have an Ra of .01 microns and leak less than .5 cc/min N2 at 3 bar, usually an order of magnitude less. That is a pretty small leak for some things, huge for others. Never tried aluminum.

 

[patprimmer]

I have used Loctite 515 for metal to metal joints, but It was mostly on magnesium or aluminium crankcases and only needed to seal oil at up to 80 psi.

It also works well as a thread seal for oil, water and fuel.

I expect they will have compatibility charts for refrigerant gasses.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[iepeulas]

What kind of connection are you working with? Threaded? Bolted flanges? Could you use pipe thread or a fitting?

There is no such thing as a zero leakage joint, there will always be some finite leak rate, especially with small molecule gasses.

I actually work for a metal seal company that makes seals with a leak rate down to 1E-10 cc per min He, which is pretty darn tight. (1E-5 is bubble tight) Typically are parts have a surface finsh of 16 microinches rms or better. Naturally the smoother the surface finish, the less leakage you will experience.

You also need to take load into account to form a metal to metal seal. The more resiliant the interface the less load you will need. A typical sealing load for metal to metal seals is 250lbs per linear inch of sealing interface.

 

[EdStainless]

Is this a connection that you have to be able to break, or is it permanent?

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