AWS
AWS D1.1
Structural Welding Code — Steel
The structural welding code, and on a piping project it governs the steelwork rather than the pipe - supports, racks, trunnion attachments to structure. Knowing where the boundary falls matters, because a weld on the pressure boundary is B31.3 and Section IX however structural it looks, and a procedure qualified to D1.1 does not cover it.
This is an explanation, not the standard. PipingInspector is not affiliated with AWS and reproduces no part of the document. Always work to the current edition of the standard itself and to your project specification.