UT weld Testing to Replace RT Testing

[humanengr]

I have a client spec. that requires RT Testing of CJP welds, and a fabricator who wants to
use UT Testing instead? I'm wondering if anyone has feedback regarding the reliability of UT testing as compared with RT. Will UT testing miss flaws that would be detected by RT?
Have you had issues with lack of permanent hard copy record from UT Testing?

The application is general structural steel fabrication inspection.

Thanks

 

[fegenbush]

AWS D1.1 6.13.3.1 (2010 Edition) relates to UT as an alternate to RT. You have not mentioned to which code you are working, but I believe that would be a good place to start.

Although the above reference allows UT of 5/16" thick material, I do not recommend its use below 3/8", as I have found the results to be inconsistent.

 

[Ron]

UT can be as effective as RT. UT can detect flaws in orientations that are not amenable to RT. RT is limited to a "straight through" approach to flaws, meaning that if the flaw is a crack that is parallel to the path of the radiographic beam, it will not be detected. UT does not have this limitation as it can detect lamellar as well as other cracks. Further, there are more limitations on joint geometry with RT than UT.

Any method is operator dependant. Make sure that the person doing the testing is certified. In the US, that certification would typically be at least a Level II ASNT certification.

The reason that there is usually no "hard copy" of the UT results is that it is the operator's interpretation of an oscilliscope image. If you were give an RT film would you be able to interpret that in accordance with the applicable code? Probably not unless you were experienced and certified for RT. You can request a screen shot of the UT image...but it won't tell you much.

UT is much more common and readily available than UT for general structural work. I would have no hesitation to use either for the appropriate application.

Background....former Certified Welding Inspector, ASNT Level 1 UT, ASNT Level 3 radiographer.

 

[Eldorado]

I concur with Ron's final words.. "I would have no hesitation to use either for the appropriate application." As he stated, each method has it's limitation. Welds come in different flavors: full penetration, fillet, plug, etc. Basically, use the right tool for the right job.