UT Shearwave of Dissimilar thickness (Butt Joints)

By FThomas Date 10-03-2008 13:38

This is the first time that I have used this forum and I'm hoping that someone may be able to answer my question.
For the past 4 years I haven't been using the D1.1 code for some time and resently I've stumbled upon something that doesn't just have me stupped. Here's the lay out;
Butt joint weld (B-U5a) welded in the GMAW process, the A1 side (bevel side) with a flange thickness of 2.5 inch and the A2 side (squared) with a 2.0 inch thickness. UT shearwave with a 72 degree probe on the A1 side (thicker side) reveals an indication at .658 deep with a severity class of -7 per AWS table 6.2. On the A2 side (thinner side) reveals the same indication but with a severity class of +3. The A1 side has full skip distance the A2 side is limited Leg 1 and the weld face is in the as welded condition both indications in Leg 1.
Here's the problem; the fabrication shop claims that I half to "evaluate" the indication from the thinner side (A2 side) basing their opinion on Table 6.2 note "a" which states "Weld size in butt joints shall be the nominal thickness of the thinner of the two parts being joined".
I disagree.. reason being- If I were to have a thickness of 2 inch's joining to 2.625 inch's and referencing AWS table 6.2 I would have 2 different accept/reject criteria, In this case I would use the thinner of the two for my acceptance criteria based upon note "a" which would be column 2 (1.5 to 2.5 inch). I'm not able to find anywhere that tells me to "evaluate" from the thinner side plus I have in my head paraghaph 6.26.6.2 (UT Butt Joint) that states each side of the weld axis shall be tested.

I've been doing UT shearwave for about 10 years and I'm also an ACCP ASNT level II and I think that anybody that performs UT knows that flaw orientation to the sound beam is critical in finding indications and as faw as the UT goes the fab shop doesn't disagree that the indication's are there. I just need some clarification as to which side I'm to evaluate the indication based upon the interpretation of the AWS Code.
Thanks for your time and any further information on this matter will be greatly appreciated.

By hogan

Date 10-03-2008 13:54

You mention your inspection angle as 72deg. If I'm looking at table 6.7 (testing angle) correctly, you need to follow procedure 1G (note 6)or 4 with F also noted. This would allow some options for UT. Unless the weld is ground flush then you should also use a 60deg. Note F also allows for further evaluation with 70, 60, 45, whichever is nearest to perpendicular. I would want to evaluate from face A ground flush, both sides of face A in the same plane, best to get it in the first leg.

By FThomas Date 10-03-2008 14:02

That's correct, I used No.4 but the 60 degree is for the top quarter the indication lye's at .658 middle half. Plust the 60 degree showed an acceptable rating, the 72 degree is the optimal angle. For the sake of the design criteria grinding the weld face flush is not an option.

By hogan

Date 10-03-2008 15:18

I think you would still be allowed to use note F for other angles. Also, have you looked at commentary c-table 6.7 for intent?

By kipman

Date 10-03-2008 17:23

Mr. Thomas,
I agree with your take on this. You are required to scan from both sides (per 6.26.6.2) and per Table 6.2 Note a you must use the thinner of the two materials to determine the acceptance criteria (moot point anyway as both 2" and 2.5" are in the same column of Table 6.2).
Regarding the evaluation of the indication, look also at 6.26.6.3. In my opinion, where it talks about "the maximum attainable indication" is referring to the max screen height. If I have to scan from both sides of the joint and one side shows the same discontinuity with higher amplitude, that is the side that has to be used for evaluation.
Mankenberg

By FThomas Date 10-03-2008 18:56

Reading 6.26.6.3, I agree it does indicate the "maxium attainable indication height". I've spoke with the contractor and they have agreed to grind the weld face flush in the area of the indication and I'm going to explore the area with a 45 degree from the A2 side and try to pick it up in Leg 1. I feel confident that the 45 degree will "nail it".

Thank you all for your help.

By hogan

Date 10-03-2008 19:48

I agree. the 45 would match the bevel face. Did you mention your X location. Is the indication at the bevel face or at the A1-A2 interface?

By Bill M

Date 10-06-2008 15:16

(B-U5a) is for SMAW. Did you mean B-5Ua-GF?

In a side view, is the thinner plate centered on the thicker plate or is one surface of the two plates parallel?

Is Face A1 & A2 on the same plane? (or is B1 and B2 on the same plane?)