Updated CRN Requirements for Flange Welds

File:PVE-4711, Last Updated: Jan 11/2011, By: LB

Per section UW-21 of VIII-1 all standard slip-on and socket-weld flanges need larger welds on the outside. The larger weld size is not required if there is no room for it on the hub.

UW-21 FLANGE TO NOZZLE NECK WELDS

UW-21(a) ASME B16.5 socket-weld flanges shall be welded to a nozzle neck using an external fillet weld. The minimum fillet weld throat dimension shall be the lesser of the nozzle wall thickness or 0.7 times the hub thickness of the socket-weld flange. See Fig. UW-21, illustration (4). UW-21(b) ASME B 16.5 slip-on flanges shall be welded to a nozzle neck using an internal and an external weld. See Fig. UW-21, illustrations (1), (2), and (3).

Fig_UW-21

VIII-1 Fig UW-21 – flange attachment weld size 

The weld size change is mandatory, but do you need to update your CRN? That depends, at the present time Manitoba and Saskatchewan say yes, Ontario says no.