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Meta to metal face seal

Meta to metal face seal

Meta to metal face seal

(OP)
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

RE: Meta to metal face seal

Like copper?

RE: Meta to metal face seal

Sounds difficult.  

A picture would be helpful.

 

RE: Meta to metal face seal

Indium will not stay put at 900C.  You'll want copper, or even gold if you could afford it.  Copper will tend to bond to steel at those temp's., gold not so much, and gold will survive more temp. cycles before it fatigues.

RE: Meta to metal face seal

you can try loctite 504.  I've used it for sealing water piping flanges.  Its made for low pressure seals.   It was checked for leaks at 125 psi without any problems.  Not sure about conductivity.  I'm sure there are several types of loctite formulas that might fit your application

RE: Meta to metal face seal

I don't think any loctite (or any polymer for that matter) will stay in place a 900C either.   

RE: Meta to metal face seal

whoops, didn't see that you don't want sealing materials  

RE: Meta to metal face seal

You need about 0.002 inch maximum over the contact surface' length and width. Surface finish is no less than 16 Ra. I suggest flashing an electroless nickel coat of 0.00050 inch depth.

Good luck with it. Standard valve problem, gate valves.

Regards,
Cockroach

RE: Meta to metal face seal

Hi!

Why not considering a single metal o-ring? this one will be good enough to make a good sealing, working at these temperatures wouldn't be any problem, and also it's a "soft solution" (because deformation) to don't worry about torque pressures

On the other hand, ceramic based seals will work also on such a low pressure

http://www.hidromar.es

RE: Meta to metal face seal

he metal to metal seals I have done was having one side with an angle that when you screw the 2 parts together, the angle meshes together to form the seal. The is how a swageloc works. I always use an oring unless its just not possible due to size or space issues. I believe the part was 17-4 ss and the part with the angle and thredas were 360brass. It was just a fitting type adapter. I didnt believe that the brass would hold up to 10,000 psi, but it did. I would have to go back and make sure it was brass. If you have room, use an oring.  

RE: Meta to metal face seal

arounhere

The point with these seals (as far as I hardly know them) is that these seals are not prepared to work under these conditions, I mean, being face seal.

Swageloc system is good while fitting 2 parts (tubes...)

http://www.hidromar.es

RE: Meta to metal face seal

Why not spiral wound gasket?

RE: Meta to metal face seal

Is there a pressure vessel seal that would work? Some of them use stainless or copper gaskets. There is probably a nuclear part that does this.

Silver plating gaskets is a good idea at these temperatures.

RE: Meta to metal face seal

I believe Flexitallic makes Thermiculite gasket material which is rated to even higher temperatures

RE: Meta to metal face seal

The ultra high vacuum industry uses a seal methodology called conflat.  Have a look a at www.mdcvacuum.com  MDC calls the flange Del Seal.

-Dustin
Professional Engineer
Pretty good with SolidWorks

RE: Meta to metal face seal

Hi!

Just like "brainstorming" (not to be critical)

Europipe: Spiral wound gasket will be good as far as maintenance will be considered, but, I think, this system would be "no maintenance". At the same time, torque tend to be higher, and temperature is a point to take care about. Regarding temperature, you'll need ceramic or metal "wound" but, on both cases, maintenance will be needed.

bcd: Thermiculite, as far a I know, is a "paper gasket" and, even withstanding such a high temperature is a "different" kind of gasket, I think, that the one needed just because it's asking good thermal conduction, and, as far as I know, this seal trend to issolate. By the way, it's a cheap solution (also to take care about)

ShaggyPE: I don't know this one, but, after taking a look at their web site, it seems to be, again, a "copper washer" working as seal. Isn't it?

Have a good day! happy shades

http://www.hidromar.es

RE: Meta to metal face seal

Well, as so often happens the OP has disappeared, leaving the rest to speculate on solutions to a problem the details of which are unknown.

Something to do, I suppose:)  

RE: Meta to metal face seal

(OP)
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.

 

RE: Meta to metal face seal

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  

RE: Meta to metal face seal

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.

RE: Meta to metal face seal

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.

RE: Meta to metal face seal

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: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Meta to metal face seal

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.  

RE: Meta to metal face seal

(OP)
Material will be stainless steel.  Fasteners: superalloy.

Bonding not an issue

RE: Meta to metal face seal

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

RE: Meta to metal face seal

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

RE: Meta to metal face seal

(OP)
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.

RE: Meta to metal face seal

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.

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