Thanks for the answers.
The combustor is a basically a type of pulse jet engine we have developed for large scale heating applications, combustion chamber and tail pipe is 321, inlet sections are 316L, its basically all a sheet metal fabrication job of rolled tubes and cones, one of the cones is made by metal spinning from 16 gauge all other parts are 22 gauge.
We build the engine from scratch, so flat sheet cut up to profiles then rolled and formed, sections welded up and also some bosses added for fuel lines and spark plug, a complete fabrication job if that answers your question:-)
Theres a few pictures on our web site www.glc-inc.ca we have made all the production jigs for forming parts but only as yet made a simple assembly jig to line up the major parts, no we are not using any jigs for parts weld up, but now you mention it I just had a Doh! moment:-)
Problems we are having is crappy looking welds with oxidization and some burn through problems, bigest problem is the back side of the weld that looks like the surface of the moon, thats the main issue as the gas velocity is high in certain sections of the engine.
edge preperation is just making them straight and square so they align, no beveling was required we thought on 22 gauge?
filler is 347 with argon and current range from 30 40 amps depending on the section being welded.
Changing to MIG is a big step yes but it was just an idea:-) since then and this post I discoverd the basic mistake I was making (Doh!) I did not clean off the oxide layer before welding! Ok I know in hindsight this was a big one but my welding experiance is limited and 321 is a hard one as I have found out:-(
Any suggestions on fixtures jigs would be appriciated or any other tips, purgeing seems to use a lot of gas any suggestions on that?
Viv