Thoughts turning to pipe-welding - but only scratching at the surface.
Obtained tuition (a long-held ambition). SMA (MMA / "stick") welding of carbon-steel pipe all-Basic in all recognised pipe-weld configurations - 1G, 2G, 5G, 6G
Explanation of those terms - you'd do much better looking on the Internet for the various explanations offered. This is the spec for the highest-properties welds you can get from SMA welding. However, the Basic-flux electrodes are not necessarily the easiest to run... The pipe positions mean: horizontal you can roll the pipe as you weld; vertical; horizontal the pipe is fixed; the pipe is inclined at 45degrees and is fixed - respectively.
So here I am practicing to try to make the techniques of the tuition come naturally. Pipe is 140mm dia and 10mm wall-thickness, while all preps are 37.5degree half-angle done manually with an angle-grinder.
Detailed issue - the weldpool appearance in Basic (7016) root pipe-welding
Considerable improvement with SMA C-stl 5G pipe root by obtaining and controlling fully-formed fluid weld-pool.
I'm a welding engineer now and I'm seeing a lot of welding procedures for TIG welding of pipe. Much of it stainless steel - a significant proportion of that being duplex stainless steel - duplex "2205" and superduplex "2507".
Time to go learn TIG welding of pipe myself so I can knowledgably evaluate such welding procedures. So here in December 2012, heading down Structural and Weld Testing Services Ltd in Sittingbourne, Kent (South-East England). Quick journey out of London Kings Cross on the "Javelin" train, BTW.
Comment and pictures on some early themes