Is running the root pass from the inside of a pipe an essential variable?

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The weld I want to perform is within all the paramenters of the Welding Procedure Specification I want to use except I want to run the root pass from the inside of the pipe (the pipe is 42").  Is the orientation of the root pass (inside pipe) a variable covered by the WPS, and if so how is it covered?  Is it an essential or nonessential variable?  How can I prove this out one way or the other.My first post, THANKS.
Reply:If you are speaking of procedure qualification for SMAW with ASME Sec IX then no it is not. Some codes or project specifications may indicate otherwise.With Sec IX you can qualifiy a procedure for 1/2" Pipe welded from one side without backing on a flat piece of plate welded from both sides. Performance is different.AND WELCOME to the forumLast edited by gaustin; 11-07-2008 at 12:45 PM.Reason: Added Welcome commentHave a nice dayhttp://www.weldingdata.com/
Reply:Yes, it is ASME Sec IX I'm trying to meet.  My process is TIG (although I don't think it makes a difference).  Just so you can picture it, I'm talking about two 42" diameter pipes joined by a butt joint.  The weld is to be produced by going insider the pipe.  I think your answer might still be right, though, that this is not an essential variable.
Reply:Is it carbon or stainless?I'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.
Reply:I'll go with Gerald on this. ASME Sec IX this is fine unless the procedure prohibits it. Doesn't matter what material, etc. The only reasons I can think of for NOT permitting it would be if there was a particular atmosphere requirement on the back of the weld (inert purge; oxygen bearing; etc). In such a case, it could be quite difficult or impossible to meet the requirement.
Reply:It's stainless steel.
Reply:im not familiar with the specfication you're using (we get to weld to navy specs), but what is the pipe for and how clean do you need the weld?  doin a root pass from the outside with inert gas running through the pipe is usually for a clean weld all the way through.   If you do it from the inside you're probably goin to end up grinding or cleaning the backside oxidation because it was exposed to air.  Is that worth it on a 42 inch pipe?"Real power is an arcair hand torch with a piece of 3/4 inch carbon and 1500 amps.  You feel like Zeus throwing a lightning bolt."
Reply:Then  duel weld the root.  Someone on the inside doing the purge on a minimum heat around the 30-35 amp range and the person on the outside doing the main 'weld', it may pay to do the same for the next run as well if it's required.  What sch is it?   You may need to qualify the procedure but it's a very efficient way to do s/sI'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.
Reply:It's 3/16".  Is that sched 40?  This brings me to another question, if anyone can help.  Is there somewhere I can get a table that converts from schedule (and gauge) to inches for pipe.
Reply:http://www.allsteelpipe.com/Pipe-Dim...ghts-Chart.pdf
Reply:Imperial      3/16" sounds like sch 10.    Standard weight pipe (carbon) is sch 40 up to 16", from there up standard weight is sch 20, but don't quote me on the 16", the memory is a bit rough at times.I'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.