B31.1 weld prep 1

[rymojo]

I have a weld prep that must comply to B31.1, but is not on round pipe, but on a 2'x6' rectangular duct made of 3/4" low carbon plate. The pressure is less than 300#.
What I want to do is to prep the weld with a square cut (no bevel) on one side, and a 45 degree bevel on the other. 1/16" gap, with a 1/2" backing strip. The backing will remain in place, and the weld is full penetration.
The big difference is that the bevel will be ground on one side only instead of symmetrical. Can anyone think of a provision in the code that prevents this prep?

 

[metengr]

As long as you qualify the welding procedure specification (WPS) with this joint configuration and it is full penetration, you have met the requirements of B31.1 (see Paragraphs 127.3. (A).2 and 127.4.2 (A)).

 

[tig360]

A 1/16 inch root opening is pretty small for a single bevel butt weld using a backing strip, you might want to consider opening up the root to 1/4" or 3/8". A slightly larger root opening will help to avoid penetration and fusion problems in the root.

 

[rymojo]

Good idea. The extra clearance in raising the new expansion joint would be welcome, too. The weld engineers at this site have accepted my suggestion for the single bevel. Thanks to metengr for the documentation to back up my argument. The total cost savings for this weld is about $18,000, and 400 mrem in dose. Now all I have to do is manage 408 inches of 3/4" weld into an 8 day window!