Figure 18 –UT Phased Array application on turret weld.
Figure 19 – Example of UT Phased Array result on some defect.
The use of new NDT: ACFM, UT TOFD and UT Phased Array, gives chance that discontinuities, which are detected by conventional methods (MPI and UT), were better evaluated (position, dimensions and orientation). No doubts that discontinuities severity and the real need of weld repair obtained by ECA (Engineering Crack Assessment) were better obtained with the use of the new NDT methods.
Some studies indicate the use of an expensive repair procedure without full reliability of success, if done in location (open sea). Docking the ship in a shipyard or in a calm bay, to make reliable weld repair, implies in interrupt the production and astronomic costs.
Because ECA studies indicates that all discontinuities are not critical the inspection recommendation was remove the minors surface discontinuities and apply regular non- destructive examination on internal defects to guarantee that discontinuities are not increasing. This procedure implies in an alternative economic and safe to FPSO operation.