Are you addressing small sized tubing (perhaps 1/2-inch OD and smaller) where orbital welding is considered in lieu of manual welding? I have seens Swagelok reference AWS D10.4 and D18.1 in addition to ASME section IX of the BPVC, B31.1 and B31.3.
Perhaps you can clarify your question with some sizing or functional considerations. For example, when speaking of tubulars with offshore structural engineers they might assume that your use of tubular components applies to the "main steel". Typically the main steel would be carbon not stainless.
