L51525 Sizing of Girth Weld Defects Using Focused Ultrasonic Beams

This project was produced to evaluate the performance of focused beams in sizing and positioning defects in pipeline girth welds. The sound beams from standard flat transducers were focused using acoustic lenses. Two types of plastics, having different sound velocities are used in the design of these lenses. One is used for the lens and the other for the wedge. The profile of the lens/wedge boundary was designed to focus the sound at a selected depth. The design takes into account the beam angle, beam diameter, focal point and working range required. The effects of test surface curvature were also incorporated into the design. This project was conducted in three phases using sample welds containing real defects, such as root cracks, slag and lack of sidewall fusion. In Phase III the individual defect size predictions were compared to the actual defects found during destructive examination. Only the readings where the signal sources could be positively identified as defects by breaking open or sectioning were included. All measurements were made to the nearest 0.5 mm (0.02 inches).