METHOD AND APPARATUS FOR PRECISE DETERMINATION OF GIRTH WELD DEFECTS

摘要

- 16 -ABSTRACT OF THE DISCLOSUREPulses of accoustic energy are transmitted atnormal incidence to the wall of a welded pipe, and also atan oblique angle thereto, wherein such transmissions, fromrespective transducers, occur immediately adjacent a girthweld. Reflected pulses are then received and processed toanalyze the radial extent of the girth weld at each inter-face between the pipe and the weld material. By thesemeans, undercuts or cracks in the weld are detected andanalyzed as to their depth and profile. The energy trans-mitted normal to the pipe wall determines the distancebetween the pipe and the pulse transducers, and a signalis then generated to simulate a reflection from the innerwall of the pipe with relation to an obliquely-directedpulse. The transducers are then moved axially of the pipeand towards the weld, in small increments, in order tocause the oblique transmission of pulses finally tointercept the weld, thereby producing reflected pulse datawhen cracks or undercuts are encountered. The heads arealso moved circumferentially of the pipe in order todetermine the circumferential extent of any undercut orcrack.