Compared to conventional ultrasonic pulse-echo (UT-PE), the combined UT-TOFD / PA technology allows greater visibility of flaws, as well as accuracy of the flaws size determination. The TOFD technique works on the basis of diffraction. Diffraction waves are formed at the tips of the surface and volume flaws, regardless of their position in the weld. Therefore, this technique can also detect pores and slags for which the classical UT-PE technique is not that suitable.
Near the surface, the UT-TOFD technique is less sensitive. This weakness is well compensated by the parallel UT-PA testing. In this way, flaws near the surface are also easily recognizable. The UT-PA technique is testing with a wider range of angles, allowing optimal incidence of the sound waves into the irregularities in the material. With the combined UT-TOFD / PA control technology, the weld scan can be displayed in several different image views, which can be documented electronically.