PAUT+TOFD inspection qualification and application of girth welds of submarine pipelines

The qualification of Probability of Detection (POD) and repeatability test needs to be carried out for the phased array ultrasonic+time of flight diffraction (PAUT+TOFD) testing of the girth welds of submarine pipelines to evaluate the reliability and stability of the application of PAUT testing technology. The submarine pipeline standard requires the use of Workmanship for acceptance, and the POD value should not be greater than 1 mm. A series of welding defects of different types and sizes were made. PAUT +TOFD testing and macro sectioning were carried out respectively. All the data of defects were recorded. Using statistical analysis methods, it was determined that the POD value under the condition of 30% evaluation threshold 90% detection rate and 95% confidence was 0.9 mm, test results showed that the PAUT+TOFD testing method met the requirements of the submarine pipeline standard DNV-ST-F101-2017 "Submarine Pipeline System" and provided reliability support for engineering applications.