Reliability of AUT systems forthe inspection of girth welds during pipeline construction

摘要

As an alternative to radiography, a state-of-the-art system for mechanized ultrasonic Jrvnspection (more recently also called AUT - automated-ultrasonic testing), for pipeline girth welds is discussed. Called RTD Rotoscan, this system has been developed for inspection of girth welds during construction of long-distance pipelines, both on- and offshore. The system is characterized by a high inspection speed and instant recording of results. Unlike radiography, it provides immediate feedback to the welders. Progress in flaw sizing and recording allowed the application of rejection/acceptance criteria for weld defects based on fracture mechanics. The development and actual use of such modern acceptance criteria, first in Canada and later also in other countries, supported the introduction of AUT. RTD, after having been the first company to offer these services, was soon followed by other providers.