4.2 UT TOFD
The use of UT TOFD, figure 16, has given the opportunity to dimension precisely the height of the discontinuities detected by conventional UT, figure 17. Additionally UT TOFD has shown that the large discontinuities by conventional UT in fact were groups of small discontinuities close to each other. Fracture mechanics studies based on discontinuities dimensions obtained by UT TOFD has proven that they are on a safe region of FAD diagram (not need of repair). As a secure recommendation the most relevant discontinuities have been time by time monitored to verify the almost improbable increasing.
Figure 16 –UT TOFD on turret weld.
Figure 17 – Example of UT TOFD result on some defect.
4.3 UT Phased Array
The use of UT Phased Array, figure 18, as TOFD, has permitted precisely obtain discontinuities characteristics (position, orientation and dimensions) previously detected by manual UT, figure 19. As the others new techniques (ACFM and UT TOFD) UT phased Array has been periodically used to ascertain that the defects are not growing.