The nozzle type and depth of groove welds are used to determine the required weld thicknesses and failure paths for the nozzle. If the nozzle is welded to the outside of the vessel wall, it is abutting the vessel wall. If the hole in the vessel is bigger than the nozzle OD and the nozzle is welded into the hole, it is inserted. Figure UW-16.1 in the code shows typical insert and abutting nozzles.