Maybe share a sketch of what the plan is?

In my mind, the need for NDT is driven by risk. A weld in a highly stressed area will need NDT, the only question is method. Since you refer to wide flanges the material is probably thick enough for UT.

Cheers, Alan

 

I think there are processes that can achieve “CJP” without open root, back gouging, or backing. Those I think are in factories that make tubing with welded seams, things were the joints are very controlled. I am aware of a process in which seams in plate up to a half inch thick are welded with sub arc from both sides with the square edges of the plates butted together. This consistently passes ndt. Even with this, though, the first pass uses a flux bed for backing just in case it penetrates too much. This is a developed process, though. To my knowledge a code book does not specify weld processes. They are pretty vague about the actual process used. It is up to the manufacturer to prove the weld process meets specs. Where i am employed the engineers wouldn’t come out to a welder and say there’s some sort of process to do this job we have, can’t tell you what, but it exists. If a new princess was needed for a job that would be taken care of king before i saw a job. Also sometimes what a customer or engineer specs is just impossible.

 

You can UT all day long, but without acceptance criteria the whole enchilada is FUBAR. If the print says CJP with back gouge as one of the steps, then do so.

Other factors are thickness of the base material, and if thin enough CJP can be achieved without bevel or gap, and backing just gets in the way. But then print says back gouge. So do it. I don't know what backing plates have to do with it, especially if the job calls for back gouge.

I weld many CJP joints without backing, bevels, or gaps. I have also had to qualify a host of CJP square bevel joints that prohibit backing, bevels, or gaps. PJPs qualified with CJP testing require macros to supplement and justify procedures. It's all in the book.

 

which weld symbol is on the drawing?

 

You can achieve the CJP by using a broader root face (if you have other side access) weld followed by root side grinding to a sound weld metal. Perform a PT before welding from back side. Otherwise you can use ceramic backing strips. If you can share the joint details, it will be more clear to advise.
For recommended joint designs, you can refer to the AWS d1.1 code figure 5.1 (there are many joint configurations).
This info will be helpful also- CJP, PJP Weld meaning, Symbol, differences and examples

 

I'm now suspecting a 'bot.