The LF weld flanges have a nice machined weld lip, generally used to interface with a relatively thin walled piece of pipe. The weld should be placed on the inside, right where the hemisphere (or pipe, if you're cylindrically inclined) hits the weld lip. Just for grins, I yanked out two pieces of LF hardware (a flange-flange adapter and an LF160 nipple) to look at the welds. Both are as Joe describes them. On the flange-to- flange adapter, the match between pipe and flange is so good, you can't tell where the pipe leaves off and the weld lip on the flange begins. On the nipple, the tubing is relatively thick-walled, so it sticks out a bit beyond the weld lip. Again, the weld was placed right at the contact point between the flange weld lip and the pipe. In neither case is there any evidence of splatter, with just a little bit of wire wheel work done to touch up the finish.
Good luck - it sounds like you are on the way to a tasty system. I'd be going that way myself, but some of the things I want to try are more easily done with a cylindrical geometry. More on that later, as time and opportunity permit.
Created on Tuesday, May 08, 2001 2:20 AM EDT by Richard L. Hester