PSI - Issue 79

Lazar Jeremić et al. / Procedia Structural Integrity 79 (2026) 117 – 123

119

3. NDT Inspection-Results The vessel 971 was inspected by 100% ultrasonic testing of 2 vertical and 3 circular welded joints, by USM 36XL Krautkramer device. Several unacceptable defects were found, the largest one marked as 1.1, located in the lower circular welded joint, Fig. 1b: length 180 mm, depth 32 mm (from 18-50 mm), positioned in the center of the weldment, reaching inner vessel surface. One should notice that MT did not reveal presence of this defect on the inner vessel surface. Results of the UT testing by combination of PAUT and TOFD applied to the same area and focused on the defect 1.1, are presented in Fig. 2. As one can see, there are two smaller indications instead of a large one obtained by conventional UT: the first one with length 53.1 mm and depth 16.7 mm (extending from 12.4 to 29.1 mm, denoted by AN1), and the second with length 18.8 mm, and depth 3.5 mm, from 46.9 to 50.4 mm, denoted by AN2. So, contrary to the conventional UT technique, two defects were found instead of one, indicating significant conservativism of conventional UT echo technique.

Fig. 2 Results of PAUT and TOFD for defect 1.1 in PV 971, [11]