Hi friends.........could someone help me?.......Why when I made UT scanning on butt welds, I had performace in both sides of welds? HAZ should be inspected too? where there is something written about that? Where I can to get anything written about that? Is important to do UT both sides of butt welds with shear wave? why?
There are fairly simple basic books and manuals on ultrasonic testing of welds and they will give you more information. I would just give you a few simple answers: Since the butt weld has two sides and any side can have lack of fusion, ut scanning is required from both sides. Shear waves are used because their wavelength is less for a given frequency and thus the sensitivity for detection of defects is better. Also, since both longitudinal and shear componenets of the ultrasonic wave are present (mode conversion) and since both have different velocities in a given material, we need to eliminate one of them so that interference between the two echoes is avoided. It is easier to eliminate the longitudinal waves (use between the first and second critical angles).
Usually the volume required to be examined is stated in the applicable code. The applicable code usually will tell you what specification you use to examine the material. For example, ASME directs you to ASME Section V. Section V, article 4 states "The angle beam shall be directed at approximate right angles to the weld axis from both sides of the weld (i.e., from two directions) on the same surface when possible."
I am glad to see you ask these types of questions as you obviously want to improve your knowledge! I am quite curious as to why you are scanning welds if you don't already know this information? Are you working under the direct supervision of a qualified level II? Or is this comment purely for training purposes?
Maybe Adalbert is in the same boat is I was many moons ago. I knew the technique to inspect weld, but didn't quite understood all the theory behind it. I got a job working for someone who believe that if you have the ticket in your pocket, you know everything. Believe me, I for one never believed it and after coming to this forum for the past three years, it confirmed it. Even more, doesn't matter who is out there, if anyone believe they know everything; think again. And many times, the code will tell you what to do i.e. scan from both side, but I still haven'e seem a code that tell you why you should. Like a lot of things it is "assume" and we all know what happen when we "assume".
Now for Adalberto, as previously stated by Swamy and William, other reasons for inspecting weld in this manner are: Longitudinal Wave of the HAZ for the detection of delaminations. If not detected, the calculation for any indication found during your shearwave inspection would be out. The other one is like Swamy said, regarding the lack of wall fusion. Basically the defect that will have the best detectability is one that is perpendicular to your sound beam. So, if you have a "V" or "Double V" weld prep, a defect may or may not show on one side of your scan.
Good day Adalberto,
Codes & standards demand to conduct Angle Probe UT Scan on both sides of butt welds. The reasons for this:
1. As the guys said; you expect to have defects at either side of the weld fusion zones. To make sure you do not miss any defect, you have to check from both sides.
2. In some cases to identify the defects and distinguish between them, you check defect signal echo from both sides; ex. Misalignment will give you large signal from one side whereas no echo from the other side.
For HAZ; Scan is not limited to HAZ. It is actually required to cover with Compression Probe the parent metal either sides of the weld to full skip distance for the highest angle probe used. To check for lamination that may interfere with your Angle Probe signals, as well as to identify the thickness; this is needed for Angle Beam calculations.