Greetings,
I am working on qualification of some PJP Single-V-groove and Single-bevel-groove butt joints for an upcoming project using 304 3,4, and 6 inch schedule 40 pipe using GMAW-P with 308 filler metal and rotating the pipe so all welds are in the 1G position.
I was told by a "knowledgeable" individual that I can prequalify these using D1.6 joints BC-P2 and BTC-P4 but I see these joints are both listed as "Nontubular". Clause 5.13 spells out the details of tubular connection requirements stating D1.6 does not address T-, Y-, or K-, connections and lists the PJP joints that are acceptable for prequalification, none of which are the joints I am looking to qualify. D1.6 defines tubular connection as "a connection in the portion of a structure that contains two or more 'intersecting members', at least one of which is a tubular member". The term "intersecting" I suppose could be interpreted as T-, Y-, or K- connections? Maybe the butt joints can be prequalified?
Looking at D1.1 clause 9.10.1 I see that "PJP tubular groove welds, other than T-, Y-, and K- connections" may be prequalified so if this were not stainless I could easily prequalify what I need to but the base and filler materials are beyond the scope of D1.1.
So I suppose my questions are can I prequalify or do I just need to do the proper PQR testing? Why would D1.1 allow prequalification of the joints in question but D1.6 would not?

D1.6 is far from perfect.

The majority of structures fabricated and erected are either carbon steel or high strength low alloy steels. As a result (my opinion), the structural committee put most of their time into D1.1, the structural code for steel. It is more extensive and more detailed than any of the other structural welding codes. Many of the other structural welding codes are modeled after D1.1 and in the case of D1.6 it leans heavily on D1.1. A welder qualified in accordance with D1.1 may be accepted by the engineer to weld the stainless steels covered by D1.6.

One of the key conditions of being prequalified is that the CJP groove weld must be made with backing or the second side must be back gouged before welding the second side. If a double sided groove weld is not back gouged, it is considered to be a partial joint penetration groove weld. In my opinion, the same approach can be applied to groove welds that must comply with D1.6. In short, if the groove complies with the configuration of a prequalified joint per D1.6 it is prequalified as long as the other considerations are compliant, i.e., listed base metal, matching filler metal, etc., are used.

In your case, you want to write a WPS for PJP groove welds. Again, in my opinion if the groove detail is or complies with a PJP depicted in D1.6 and if all the other conditions are met, there is not need to qualify the WPS by testing.

The copy of D1.6 I have is 2007. Clause 3.20 states that the joint details included in Figure 3.4 and Figure 3.5 are prequalified without the need to perform the tests included in clause 4. Prequalified T, Y, and K weld details are shown in Figure 3.6. I consider all the joint details depicted in Figures 3.4 and 3.5 to be applicable to both nontubular and tubular connections because D1.6 does not include a separate section on tubular joints or specific prohibitions.

Is there something I'm overlooking in your post?

Al