D1.1 UT question

Date 06-21-2009 02:16 Edited 06-21-2009 04:40

I have a few questions concerning UT of double bevel groove welds.

The joint is a double bevel groove T joint with 1 3/4" plate (continuity plate) welded to a column flange and web.

D1.1 table 6.7 directs you to use procedure # 4 which has you use a 60 degree probe for the top quarter of the weld and a 70 degree probe for the middle half and bottom quarter.

Question 1.) What determines which face is face a and b if the bevels of prep are of equal depth? In the table 6.7 legend the note at "A Face" says the face of the material
which initial scanning is done. This is a bit ambiguous to me.

Question 2.) If you are unable to determine which face is face A then how do you know which area of the weld to scan with the 60 degree probe? In this case it would be
the "top" quarter of weld thickness. I am of the opinion that flaws in the area of the weld thickness indicated in the procedure legend should be evaluated with the
indicated probe angle.

Question 3.) Is it acceptable to use a 70 degree probe in the first leg from both faces A and B? Seeing how that is the angle preferred by AWS for flaw detection.

I feel that table 6.7 is not as clear as it could be and that in procedure #4 the use of a 60 degree probe for the top quarter of weld thickness is intended for scanning joints of that thickness from one side due to the 60 having a shorter sound path, which makes sense. Or am I just approaching this wrong and should one scan welds from one face only?

By Taintedhalo (*)

Date 06-22-2009 16:56

If you are able to scan from 2 diffrent faces then you should. Some times the discontiuity is at a angle that does not reflect the sound that well from one face but from the other face it makes a good reflector. Think of a slash mark(/), That is why you should scan from 2 diffrent faces. The easiest way to figure out wich side is which is to locate a starting point (end of part) then usually the upper part is "A" and lower is "B", the T-Joint you are asking about it would be the top side of the plate that is beveled would be "A", and if it is a butt weld then "X" will be you center line of the weld then it works the same "A" will be above "X" and "B" will be below "X".

The reason for the smaller angle transducer on thicker material is so you don't have to travel as far away from the weld to reach the top of the weld. To see this draw a rectangle on a piece of paper and then pick a spot on the upper line towards one of the edns of the rectangle and mark with a "X". Then draw a line at 70deg from that "X", we will call that the sound path. Next from that same "X" draw a line at 60deg., now notice that the 60deg sound path is shorter then the 70deg sound path. That is why then want you to use a smaller degree transducer for thicker material, you can stay closer to the weld and not loose sensitivity due to long sound paths.

Hope this helps and if I am wrong then someone will correct me. (I hope).

By mroach

Date 06-23-2009 04:30

trapdoor, Your right, with a double bevel tee joint, face "A" is your call. Just make sure that which ever side you pick is consistant for traceability. Look at the testing angle general notes, particularly the 1st and 3rd. At 1 3/4" thickness you are right at the border of procedure legend 1 or 4. Either way full examination of that joint on the 1st leg from one face, considering weld profile and the distance from the index point of the shoe to the end of the shoe, is not possible with either the 70 or the 60. Now considering testing angle general note 3, full coverage of the weld from one face is attainable by evaluation from the second leg. Bear in mind though if this is a cyclically loaded tension joint then testing angle general note 5 comes into play. Considering your planning on using procedure legend 4 on this thickness full examination coverage is possible. Just figure out at where the top, middle and bottom quarter depths are at. The middle and bottom will be evaluated with the 70 on the first leg, however the upper quarter with the 60 will be on the second leg. I agree with taintedhalo, depending on the orientation of the reflective surface, the indication may reflect higher from the opposite face. Seen that many times. Thats why I would emphasize to be consistant in identifying face "A" so results are consistant. Best of luck MR

By trapdoor (**)

Date 06-24-2009 00:23

I forgot to mention that some of the plates are 2 1/4 as well.

By mroach

Date 06-26-2009 21:07

2 1/4" would be procedure 4. Since you are setting up on that for the thicker material anyhow, why not just scan the 1 3/4" the same way. The 70 evaluation will still be the middle half and bottom quarter on the 1st leg and the 60 evaluation in the upper quarter on the second leg. Might not hurt to map out the joint profile so you can tell where the fusion surfaces are at. Depending on the type of material, the midline grain will play havoc with the 70 scan considering how much gain you will need to add. The straight beam scan should indicate, to some degree, what kind of noise to expect. Thats a big Tee joint, good luck! MR