welding performance of less than 3/8'' and without backing

Date 07-14-2020 09:31

Hi all,

I was wondering - we are starting a project that includes plates ranging from 6 to 8mm (0.25-0.325''),
where most of the grooves are single bevel without backing.

I saw that D1.1 states that the minimum thickness for welder qualification is 3/8'' - which doesn't make a a lot of sense -
buying a thicker plate only for the qualification.

Moreover, table 4.11 refers to figures 4.20 & 4.21 which shows 3/8'' plates been welded with a 45 deg. V groove & a backing plate,
If I would do so - according to table 4.12 - the ommision of backing (which is my case exactly) - won't qualify the welders.

does anyone has an idea what should I do for the WPQR?
use a 3/8'' plate? make a groove instead of bevel groove? use a backing plate?

Thanks.
Shay

By welderbrent (*****)

Date 07-14-2020 13:32

Good Day Shay,

The standard welder qualification test is different from some things you will run into in production.

Once the standard test is taken the welder is qualified to weld 1/8" to 3/4". The 1" test will qualify them for unlimited thickness.

But, looking at the preapproved joints in Clause 3 Figures, you will notice that open root, single bevel, with no backing is not a preapproved joint. This is because of the stats that were used when setting up the program. In an effort to assure the highest probability of success in welding, certain materials, joints, processes, and other restrictions were arrived at that have been used and proven successful for a long time.

Now, per your query, not using backing is not an issue if there is backgouging involved. But, if you are only welding from one side you need to perform a PQR to prove your process and technique will work. Then, the welders would have to be tested to the WPS developed from the successful PQR. But, your welders still need to be tested and qualified per the standard test from Clause 4 (Clause 6 in the 2020) of D1.1.

Now, following that train of thought, if you use the standard test, and the welders are welding from one side of a joint, but backgouging is used to finish the weld, they are good to go. Everything else only applies when no backgouging and welding is done from the second side.

The answer to your final questions cannot just be a judgement call that we make for you. You must decide exactly what is needed and how the production welds are to be done. Giving us more information will help us to give you any more guidance that may help you to go the direction you need to go.

Have a Great Day, Brent

By 803056

Date 07-14-2020 16:34

What is the governing code? If D1.1 is your governing document, you need to do what it says or ask the Owner to approve something as an alternative.

Perhaps your customer would be satisfied if your welders were qualified in accordance with AWS B2.1, but you would also need to qualify a WPS that was open root in order to qualify your welders without backing. That is, unless your client would be satisfied with a "mock-up" which could be evaluated to meet the Owner's (customer's) needs. The customer (through his engineer) holds the cards in this game.

You didn't say exactly what you were building. That could play a part in deciding what route to take and whether or not your customer would agree to accept an alternative.

Al

By ShayKe

Date 07-15-2020 14:19

Thanks Brent & Al,

The governing code is indeed AWS D1.1 - but the steel is european - S690 QL.
I'm going to qualify the process - and by that qualifying one of the welders. but I won't do it for all of the welders..

The process qualification will use a 0.25'' plate with a bevel groove (with around 0.05'' root face with zero root opening),
welded from one side only, without backgouging.
It is similar to the design and to what I believe is the most difficult welding situation we have in the project .

correct me if I'm wrong - the code gives me the following options:
1. prequalified situation - not going to happen for european steel.
2. qualify the welder using the procedure qualification.
3. qualify using D1.1 figures 4.20 & 4.21 (using the parameters listed) - and qualify the welders to weld with backing.
4. qualify using D1.1 figures 4.20 & 4.21 (using the parameters listed) - without backing plate and qualify the welders to weld with backgouging.
the last 2 won't help because we won't be able to backgouge or to put a backing plate in the actual work.

Why isn't there an option like in figure 4.17 - to use a configuration of a qulified WPS?

Maybe addressing the owner (engineer) is the way out as if it was B2.1 -
asking him to allow the welders qulification to be based on the qualified WPS.

Thanks again.