A new requirement was added to the 2019 Edition of the ASME Code in paragraph UHX-4(h), concerning openings adjacent to tube sheets. In exchangers where the tube sheet is welded to the shell, the stresses in the shell are increased near the tube sheet. The code now specifies a minimum distance that nozzles must be located from the tube sheet, to avoid this higher stress area. The requirement also applies to nozzles in channels that are welded to tube sheets. Smaller sized nozzles are exempt from the requirement.
