We as RTD have experience with al these techniques we booked good results with the eddy current system to detect corrosion under isolation and we have also have digital RT available to detect CUI there is also an other solution to detect CUI that is with long range ultrasonic.
for extra...
If you check RTD website we have Pipeline inpection tool we can check online (pig goes in and we look real live on the screen if there are any feature)we a have lots of exeprience with riser inspection. and its no problem to detect/find this 3mm feature
http://www.rtd-group.com/
We did lots of test to compare RT with tofd (time of flight diffraction) and we found that tofd has a POD of more then 90% (RT 60%). But TOFD has also it limitations a wall thickness below 1/3 of an inch RT has better results. For carbon steel it is the ideal replacement for RT in the feature...
