Skrinkage of S.S. flange

By les Date 04-17-2002 19:00

I fision welded an 8" S.S. knife edge flange onto a 6" tube. After welding, the copper seal doesn't fit. I didn't try the seal on the flange before welding so now I don't know if the flange shrunk or if it never was big enough. The flange is now about .020" too small for the seal and it is no longer round. The out of roundness most certainly comes from the welding but that much shrinkage puzzles me. The whole chamber was to be annealed after being put together, is there any hope that annealing will allow the flange to open up? That is of course assuming that it did shrink.

Thanks

Les Lorenz

By Niekie3 (***)

Date 04-18-2002 17:40

I don't quite understand the term "knife edge flange". I assume you are referring to a butt-weld flange? If so, then I can not believe that you experienced any significant distortion on the flange face. I have certainly never seen this happen.

If I am misinterpreting the "knife edge flange" term, then please give an explanation for this term.

Regards
Niekie

By les Date 04-18-2002 20:28

I think you got it right. A knife-edge flange is a flange that instead of using an o-ring to seal, it uses a sharp edge that bites into a flat copper washer. This gives a better seal for high vacuum chambers. I have talked to other people about this problem and it was the consensus of all that the flange would not have changed that much in welding. So I'm going to assume that the counter bore for the copper ring on the flange was made too small.

Thanks for the reponse.

Les