The technique for automated ultrasonic inspection of pipeline girth welds is based on the so-called zonal discrimination approach, commonly used today in the oil and gas industry. For each project, qualification of the inspection equipment and procedure according to DNV standards (DNV OS F101, DNV recommended practice: DNV RP F118) and TOTAL internal specifications, is required to ensure inspection performance. Some of the qualification tests based on the inspection of defective welds are costly and time consuming. Moreover these tests don’t provide the opportunity to thoroughly investigate the influence of several parameters such as wall thickness variations, sound properties, beam characteristics, and defect orientation on the probability of detection (PoD) and sizing accuracy. For these reasons, introducing modeling into the qualification work to replace part of the tests currently performed and add other relevant tests that would otherwise be excluded brings added value to the qualification process. The first stage of the project was to qualify the use of a modeling tool to simulate phased-array UT inspections performed with the PipeWizard system. To do so, results of qualification tests performed for a project on pipe welded sections exhibiting both machined (typically notches and flat bottom holes) and real weld defects (typically lack of fusion, lack of penetration, porosities, etc.) were used. EXTENDE modeled the qualification mock-ups and the UT inspection procedure with CIVA software. Then, calculations were performed to compare simulations and experiments. The results of this first study are a promising beginning to the use of CIVA calculations in the qualification process of UT inspection of pipeline girth-welds, particularly for PoD and sizing accuracy evaluations.

Related Publications