Welding to Section VIII Div 1. Butt welds only?

Some type of small fittings are allowed to be attached using fillet weld from one side only, see UW-16(f)

There are rules for both in certain circumstances. Nozzles may be attached by fillet welds only following Code rules.

Gavin_UK said:

Can some one help me with understanding what welds are permitted in a pressure vessel to Section VIII, Div 1. (I am looking at 2023 version)
UW-9 a Seems to pretty clear state only Butt welds can be used for retaining pressure....
"Only butt-type joints may be used with the permitted welding processes in UW-27 that include the application of pressure"
But then later, in UW-13.1 it shows fillet welds being used to attach Heads to shells.
If these fillet welds are retaining pressure what is?

Any help appreciated.

Gavin

Click to expand...

For common attachments you may refer to UW-13 figures
For nozzles you may refer to UW-16 figures
For tube to tubesheet joints you may refer UW-20 figures

Kindly note is your job is U-Stamp you have to draw figures and mention the appropriate figure numbers in your drawings

In UW-9, "with the permitted welding processes in UW-27 that include the application of pressure" means that the welding processes themselves include application of pressure to the joint as part of making the weld. Processes like resistance welding, flash welding, and friction welding that involve heating the faying surfaces of the joint to welding temperature and then forcing the parts together (i.e. applying pressure) to achieve fusion. So for example you would be allowed to use one of these processes to attach a head to a shell using a butt joint, but not to attach a nozzle to the side of a vessel with a T or corner joint.

It is not referring to welds that are SUBJECT to pressure during operation, of which there are any number of non-butt joints permitted for various purposes (as you noted one example).