I presume this is an in-service repair versus new construction? If yes, then pending the review by a registered Professional Engineer (experienced in pressure vessel design) and in accordance with the requirements of ASME Section VIII, Div III, welding can be performed following the rules in the NBIC.
Thanks. This is what I was assuming, but it was always "drilled" into our head that no welding was ever permitted. I think this was more to prevent anyone from simply "tacking" on a bracket or something that might jeopardize the vessel's integrity.