Development of a 3D Ultrasonic Inspection Device for Pipeline Girth Welds

Quality requirements for girth welded joints in gas pipelines necessitate adequate penetration to the inner surface and no harmful defects. Toho Gas has completed development of the world’s first inspection system applying the ultrasonic synthetic aperture method for welds in steel pipes used to carry gas (external diameter 200mm, pipe wall thickness 5.8mm). In recent years, ultrasonic phased-array technology and ultrasonic TOFD methods etc. have attracted attention. However, the ultrasonic synthetic aperture method is an imaging technology that is superior to these, as it can synthesize several thousands of wave form data at high speed, its image clarity is the best in the world. The four features of the system are (1) the ability to provide an image of the interior of a weld, (2) the ability to quantity incomplete root bead penetration, (3) automatic high speed collection of data, and (4) data base management capability. The ultrasonic synthetic aperture method simplifies defect judgments because it does not require that operators possess special qualifications and training. It can produce three-dimensional high picture quality data. It can be handled easily at work sites because it is portable. This report describes the ultrasonic inspection system development process and the results of trial inspections.