Meta to metal face seal

[asimpson]

I have been tasked to make a metal to metal static face seal for steel cycling between 20 and 900C to contain steam at maximum 5 bar.

No gaskets or extra sealing materials. Good contact between sealing faces for thermal conduction. About 100-150mm sqr. similar to flange or manifold and bolted together.

What sort of flatness would be required for a for a steam-tight seal?

I might be able to use soft metal gasket but it would have to make good thermal contact.

Any thoughts welcome?

Many thanks

 

[asimpson]

Still here. Just taking in ideas. I think most people understand the problem, judging their suggestions.

I would preferr not to use gasket and just have flat face contact of two steel flanges.

 

[SnTMan]

asimpson, yeah I believe that much was understood by all. BUT many things not known, among them:

How are sealing faces clamped together?
Approximately how much real estate is available to the seal?
What manufacturing processes are available?
Few pressure cycles or many?
Short service life or long?
Cheap or expensive?

So you get, for example, Hidromar brainstorming over ideas put forth by Europipe, bcd, ShaggyPE, to what end?

A problem well stated is a problem half solved

Regards,

Mike

 

[btrueblood]

Do you need to regularly break and re-make this seal? Then a steel-to-steel flange is not a good idea; the metal will diffusion bond under the clamp load at those temperatures. The use of a soft metal gasket is preferred, and the more noble (oxidation resistant) the better, and the more ductile the better (to resist fatigue due to thermal cycles). Thus people pointing you to copper, silver, gold. Realize that at those temperatures, there is likely to be bonding of those alloys to the steel also...but at least they are soft metals and easily* scraped/sanded/ground back to the parent material before re-make.

* relative to a diffusion-bonded bare steel joint.

 

[gadkinsj]

My corvair has an Aluminum to Steel interface in the combustion chamber. Gm saw fit to put .032in. Copper Gaskets between these 2 surfaces way back in 1960. If you could get good reliable metal on metal sealing that doesn't destroy itself with heat cycling, then we would have dispensed with gaskets in car engines long ago.

 

[KENAT]

Crazy suggestion that I haven't really thought through but...

Could you copper plate one or both of the mating surfaces thick enough to act as a gasket? Quick Google search suggested you could get at least .015" thick in the correct situation.

You might even be able to put a gold layer on top of this to address the diffusion bonding issue.

(Please note, I'm completely pulling this out of my a$$ and haven't thought it through or researched it at all.)

Posting guidelines faq731-376

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[dvd]

Steel at 900C and fastener at 900C? Is the steel actually stainless steel? What material are the fasteners? Seems like tension on the joint will be difficult to maintain due to thermal growth differences.

 

[asimpson]

Material will be stainless steel. Fasteners: superalloy.

Bonding not an issue

 

[SnTMan]

After only thirteen days of discussion we have now learned joint member materials and that it is bolted. We are making progress.

 

[asimpson]

I think I mentioned steel faces boled together in my first post.

 

[KENAT]

No, you mentioned bolted together but I don't' think you gave a material.

I wondered how you were going to get the fasteners to hold in mercury at those temps but let it slide.;-)

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[asimpson]

As far as I can judge the consensus seems to be a metal to metal seal for steel flat faces to contain steam seems to be a silly idea. Never the less my boss wants me to try it out. I will probably end up using a copper gasket . At least that has a good chance of working.


Thanks everyone.

 

[HDS]

http://www.parker.com/literature/Seal Group/CSS 5129.pdf

 

[saplanti]

Please note that you cannot call your flange connection metal-to-metal contact flange connection in case the metal-to-metal contact is not maintained during installation and tightening. I suggest you go through the following threads to understand:

http://www.eng-tips.com/viewthread.cfm?qid=313354

http://www.eng-tips.com/viewthread.cfm?qid=313472

Hope it helps.

Ibrahim Demir

 

[pierdesign]

Hi. I did something that might be similar, given your minimal description. The assembly was stainless steel, copper o-rings*, cobalt foil, polished 420 stainless steel. This assembly used dry gases at up to about 1800 psi, not steam.

*Copper o-rings were actually partially etched from contiguous copper shim. Multiple separate copper o-rings were too difficult and failed too often.

Metal bonding was not much of an issue, localized rusting of the stainless steel due to intimate copper contact was an issue.

Parts of this are patented.