Method and apparatus for precise determination of girth weld defects

摘要

Pulses of accoustic energy are transmitted at normal incidence to the wall of a welded pipe, and also at an oblique angle thereto, wherein such transmissions, from respective transducers, occur immediately adjacent a girth weld. Reflected pulses are then received and processed to analyze the radial extent of the girth weld at each interface between the pipe and the weld material. By these means, undercuts or cracks in the weld are detected and analyzed as to their depth and profile. The energy transmitted normal to the pipe wall determines the distance between the pipe and the pulse transducers, and a signal is then generated to simulate a reflection from the inner wall of the pipe with relation to an obliquely-directed pulse. The transducers are then moved axially of the pipe and towards the weld, in small increments, in order to cause the oblique transmission of pulses finally to intercept the weld, thereby producing reflected pulse data when cracks or undercuts are encountered. The heads are also moved circumferentially of the pipe in order to determine the circumferential extent of any undercut or crack.