TOFD instead of RT 3

[shahdadf]

dear friends,
our vendor is insisting on this matter that for Cr-Mo steel material he uses TOFD instead of RT..is it possible and acceptable???
thanks a lot,

 

[metengr]

TOFD is a form of ultrasonic examination. It is an acceptable form of volumetric examination for most Codes and Standards, provided all parties are in agreement as to acceptance criteria and technique. The TOFD method is more sensitive in comparison to RT for radial/planar flaws in welds and base materials.

 

[SJones]

1. Make sure that the company has a good level 3 NDT qualified to ISO 9712 and not ASNT and that they, and all the level 2 personnel, have documented training and experience on the system concerned.

2. Acceptance criteria can be very tricky. There is an ASME VIII Code case (2336 perhaps ??) that can give you guidance. There may be a very recent EN standard which will probably be superior as it is based on a lot of collaborative research.

3. If you are deploying inspectors, make sure that they know what they are doing with TOFD.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[0707]

TOFD and RT being different NDT are used to detect different defects one can not honestly say that he can use one instead of the other they are some times complimentary.

The skill operator’s exigency is grater for the TOFD than for RT operators.

When you request a TOFD service you should be aware of the skills and experience of the operator to have the right output from the test and interpretation of the results.

Luis

 

[UltrasonicMan]

2235 is the code case for TOFD for Pressure Vessels only. Also must be sure thcikness is greater than .500". Keep in mind that TOFD has "Blind Zones" at both the ID and OD, and as such, must be combined with shear wave probes, two aimed at the root, two at the cap, usually 45 and 60 deg respectivly. In my opinion, it is far better to combine RT with TOFD.

Regards