Hi moseley,
I understand what you're saying and I might be a little rusty on Sec IX but am I not correct in the answer to his question? He didn't ask how to test his welders, he asked-
"to qualify a welder for 1" thru 8" diameter pipe with W.T. ranges of 0.188" to 0.500"
He didn't ask what would be the easiest or best diameter to test with nor did he give any indication as to what process(s) he was using to perform them or what materials he had on hand to used as coupons. I would believe he was looking for some accurate, but general info rather then precise because of not noting his particular circumstances or conditions.
If he had asked for advice as to which diameter, regardless of process he should use , I would have advised him to use either 11/2 or 2" sch 160 if he can get it. One set of tests with unlimited diameter qualifications over 3/4" NPS (1" OD) and wall thickness limitations to 688". I realize in some industries the 6" test is standard but not necessarily in the chemical, possibly because of the variety of smaller pipe sizes used. If he can't get the heavy wall then he'll have to do something similar to your suggestion.
With your scenerio I believe he has to take at least two different sets of qualification tests just because of the 6" diameter test restriction of 2 1/2" NPS. On top of it all, it's common knowledge that the skill level to successfully pass a qualification test goes up as test coupon diameter goes down. The old excuse I've heard a lot over the years about welders using 6" coupons was that they use more filler to that must means they have more opportunity for error. Sure you use more filler to do the 6" and it is only an excuse in my opinion because there's not the twist of the wrist you need to successfully complete a 2" or similar diameter test with the 6". In addition, with the smaller diameters, radiography is preferred rather then strapping and bending, which from my experience is far and away the best way to critique a test weld unless it's a GMAW(SC) test of course. I've seen more then enough 6" qualified welders (stapped & bent) over the years that couldn't concistently pass a B31.3, Normal Fluid Service criteria radiograph to save their souls, let alone pass a 2" qualification test that is radiographed!
Regardless of what rick028 does or what we think he should/could do, let me pass on an old adage that was given to me as sage advise almost 40 years ago and has never failed me- "A welders qualification test is only a license to make his first production weld on your job, after that it's your job to see if he keeps it " Seldom
"There's no such thing as a welding problem, there are only welding puzzles of assorted sizes!"
