Enhancement of weld coverage and localization of defect through geometrical modeling for ultrasound inspection of TKY weld

While inspecting on tubular TKY joints, ultrasound travels into the weld cross section from an elliptical surface whose profile changes along the weld seam. The complex geometries of the scanning profile cause two challenging issues for ultrasound inspection: existence of dead zones and localization of a defect. This paper derives the parametric formulations to systematically model the weld cross section profiles. With the established models, the profiles are constructed to visualize ultrasound beam simulation in order to maximize weld coverage. Simulation on typical positions along a Y joint is conducted using 5MHz, 16 and 64-elements phased array transducers. Transducer placement has been simulated and adjusted to determine scanning strategies. 98~100% of the weld can be covered mainly from the branch pipe side, while at some locations supplemented scanning from the main pipe side is necessary. Sectorial scanning data on a real Y weld is analyzed and then overlaid with the built weld cross section profile enabling intuitive defect localization. Defects are identified at two different locations and their depth and height is also estimated.