Figure 3.4 of AWS D1.1 only shows the prequalified full penetration groove welds. If you want to use a full penetration groove weld joint design that is not shown there, you can if you qualify it.

I have also noticed that AWS D1.1 has much more strict guidelines in some areas than ASME IX. I can't tell you why, but I'm sure that a lot of the newer & stricter guidelines came out of the Northridge Earthquake failures that were studied.

G. Roberts

In part reply to Question 1:

According to ASME VIII, single sided welding that results in the same quality of weld without back gouging, as you will obtain with back gouging is considdered to be the same a double sided weld.

In ASME VIII, while the quality of the weld is a contributing factor to the joint efficiency of a weld, it is primarily determined by the extent of the radiography.

In reply to your last question:

I believe that D1.1 when taken as a whole, is much more "lenient" than ASME IX. (General use of pre-qualified procedures etc.) Because this more lenient aspect of the welding section of D1.1 is used most widely, it does not address all the issues that ASME IX does with respect to the qualification of procedures.

Regards
Niekie Jooste

So far nobody has answered Question 2, so I'll give you my opinion. If it's wrong, someone please correct me.
ASME IX is directed primarily (although not exclusively) to pipe and plate welding. AWS D.1 is directed primarily (although not exlusively) to structural steel welding.
You've mentioned mixed welding, i.e., that employing E6010 for the first pass and E7018 for the subsequent ones. This is a technique I have used extensively back in my days of erector engineer for welding carbon steel pipe, especially (although not exclusively) when welding oil and gas pipelines. Why? Because those welds are subjected to radiographic inspection and E7018 is the indicated electrode. However, E7018 has poor penetration properties, so the first pass is given with E6010 (or E7010) whose penetration is excellent. Once you've got the proper penetration, the subsequent passes may be given with E7018.
On the other hand, AWS D.1 is for structural steel, where most weldings are fillet ones, which are not radiographed, so you can use directly E6010. When you have butt welds, such as for joining two steel shapes (H, or channel, or T, or angle) together, you can weld from both sides of the steel to assure good penetration, which obviously you can't do in a pipe.
So, when welding structural steel you don't need to use the mixed welding technique, and that's why AWS D.1 doesn't take it into consideration. On the other hand, as ASME IX applies to pipe, where the mixed welding technique is extensively used, it's taken into account in that Code, and also, although you havn't mentioned it, in API 1104.
Giovanni S. Crisi
Sao Paulo - Brazil

Part 2 of question 1: If the weld meets the acceptance criteria of UW-35 and is proven by RT examination - yes. Otherwise, if you look at Table UW-12, it seems the answer to your question is no. 0.60 is the highest efficiency you may get from a single welded butt joint without backing (type 3 joint). I believe the intent of Section VIII is require RT before you may consider the efficiency 1. Bear in mind that you must have a qualified procedure with open root.

Part 2 of question 2: As long as you have a PQR to support each of the filler metals/base metal combinations you may combine procedures. You are limited by base metal thickness for each PQR (reference in QW-200.4 to QW-451), and for deposited weld thickness. We have one PQR that includes 6010 for the root & hot passes and 7018 for the remainder. It eliminates the need to become an ASME lawyer. If you are interested, there is an ASME Section IX guide that helps explain some of the confusion: CASTI Guidebook to Sec. IX, author Mike Houle. May be purchased by calling (780) 424-2552.

Question 3: Pressure parts have more uniquely defined stresses as compared to structural welds. There is a lot of readily available engineering to contemplate. Unfortunately, the welding industry has created a pecking order with structural welders at the bottom and pipe/tube welders at the top. True, pressure vessels contain potential energy and lethal products, but I think we can all agree that fracture critical bridge members can be just as deadly if a weld fails (as a boiler). I used to think structural members were "less important" than pressure part welds. That belief was based on my own ignorance. To answer the question, perhaps AWS is aware of the hierarchy that puts structural welders low on the pole and because of that, they set the acceptance standards higher in an attempt to weed the worse welders out. Sorry for the soap box, Charles Hall