Ultrasonic or Radiographic inspection?

Date 04-06-2004 16:38

Hello.

We have a technical discussion about the reliability to use Ultrasonic testing in ASTM A36 butt welds with 11 milimiters in thickness instead radiographic testing. The welds are located in main structural weldments and we are heard that is necesary use special techniques in order to obtain a good detection with UT in this thickness (AWS D1.1 allow use it in 8 mm). ¿Wich is the best method for this thickness, UT or RT?
Thanks for any help about it.

Jorge Giraldo
Medellín, Colombia

By jwright650 (*****)

Date 04-06-2004 17:31

What is your joint design? In my opinion, UT will find indications that RT won't, and visa versa. It really depends on the orientation of the indication(s), and the joint design may dictate which method to use to find what you are trying to detect. The key is to evaluate the weld with a source that is perpendicular to the orientation of the defect for best results.
John Wright

By vonash

Date 04-06-2004 17:49

I agree with John. RT is good for thin materials; UT is as good, if not better, depending on the technique, procedure, equipment, and ultimately, the expertise of the operator.
Regards,
VONASH

By NDTIII

Date 04-06-2004 19:30

If you're using a standard weld prep and a standard welding process, then either UT or RT can be used effectivley. The only difference from what I could see would be the cost.
When you get into your narrow joint designs and automatic processes, RT becomes less effective and UT more effective.

By thcqci

Date 04-07-2004 16:31

Sound advice above. One advantage to RT is the permanent record to demonstrate compliance and soundness (as long as radiographs meet minimum requirements). Whereas a less competent UT inspector may miss something, the radiograph will stand as a permanent record for others to interpret and verify also. Having dealt with an incompetent UT inspector here in the past, this is a sore point with me. Anyone can miss something sometimes, but repeated misses with poor technique doesn't get it. We don't use that company anymore; now I do my own. RT will cost more money though in addition to limited access around weldments during the exposure time.

By H. Chang (*)

Date 04-08-2004 03:17

A butt-welded joint of 11mm of SA-36 steel, RT will be the best choice as thcqci recommended, if cost is not your most important concern. In pressure vessel & boiler field, RT is mandatory, except that for joint configuration makes the RT impossible.