Mechanized UT now can replace RT on girth welds during pipeline construction
- Roentgen Technische Dienst bv, Rotterdam (Netherlands). Development and Systems Dept.
As an alternative to radiography, a field-proven mechanized ultrasonic inspection system is discussed. Called Rotoscan, this system has been developed for inspection of girth welds during construction of long-distance pipelines, both on- and offshore. Rotoscan is characterized by high inspection speed and instant recording of results. Unlike radiography, it provides immediate feedback to the welders. Recent technical improvements in flaw sizing and recording have allowed the application of rejection/acceptance criteria of weld defects based on fracture mechanics. The development and actual use of such modern acceptance criteria, particularly in Canada, supported the introduction of Rotoscan. Commercial applications in Canada and Germany proved that, contrary to expectations, ultrasonic inspection in combination with mechanized welding does not lead to higher weld repair rates than radiography does. Between early 1989 and the summer of 1994, over 3,000 km of pipeline (200,000 welds) were inspected. Recent introduction of Rotomap enabled the system to cope with most existing UT procedures and acceptance criteria, because of its capability to detect and quantify volumetric defects. Moreover, the integrated TOFD option enables defect height sizing. The present Rotoscan is capable of achieving a high Probability Of Detection (POD) together with a low false call rate, appropriate flaw sizing capabilities and transparent recording of results. In the meantime, Rotoscan has been qualified in various countries, for different customers and for a variety of weld processes and wall thicknesses. Because of its features, the now mature Rotoscan has demonstrated its capabilities for use on lay barges as an alternative to high-speed radiography.
- Research Organization:
- Roentgen Technische Dienst NV, Rotterdam (Netherlands)
- Sponsoring Organization:
- American Gas Association, Inc., Arlington, VA (United States)
- OSTI ID:
- 446399
- Report Number(s):
- CONF-9509277--1; ON: TI97003375
- Country of Publication:
- United States
- Language:
- English
Similar Records
Toward practical 3D radiography of pipeline girth welds
Evaluation of pipeline girth welds using low-frequency horizontally polarized waves