Nice drawing!!!, Bill Jepson.  Thanks - picture's worth a thousand words.

 

When I asked the question, I was thinking about welding, for example, a 1 foot piece of pipe to another 1 foot piece of pipe.  Had totally missed that the discussion was "pipe-to-flange".

 

Thanks to all for clarification.

 

David

Always happy to help when I can David. FWIW I work in the semiconductor and vacuum industry and they have these super trick orbital pipe welders that mechanically rotate around a tube making a perfect full penetration joint. These would work for headers too. They wouldn't have a problem with stainless as that is what all their piping is made from. Usually 304 or 316, 321 welds easier than 316 if I read the books right. They need about 3/8 of straight on either side of the weld. You can't believe how perfect these welds are. You would have to have the tubes cut to length, but these can be done for surprisingly reasonable money. They have to have PERFECT reliability too as they often carry pyrophoric gasses, (They catch fire on contact with air), and any leak would be disastrous!

 

Bill Jepson