Automated Ultrasonic testing of Pipeline Girth Welds, its Present Status and Future Developments

抄録

Mechanized or Automated Ultrasonic Testing of pipeline girth welds is now in common use in the on - and offshore industry. Automated ultrasonic testing (AUT) is globally seen as more than just an alternative to the standard radiographic inspection technique not only because it does not poses safety hazards but also because it is faster, more reliable and has better detection capabilities of critical Lack of Fusion defects in pipeline girth welds. One of the reasons to use the AUT technique is due to its possibility to use acceptance criteria which are based upon ECA (Engineering Critical Assessment) instead of the so-called "Good Workmanship". Usually the AUT systems are mounted on a band strapped around the pipe. From the weld, ultrasonic data is collected from which the defect sizes and positions can be determined by experienced operators using dedicated software algorithms. This paper discusses the RTD Rotoscan system, which is the first worldwide AUT inspection system for new construction pipeline girth welds. The principles of AUT, the conventional RTD Rotoscan as well as the RTD phased array Rotoscan and its advantages in comparison with conventional (multi probe) AUT are discussed. Furthermore challenges regarding the use of AUT on Austenitic welding having a corrosion-resistant alloy layer are presented. This paper describes also latest improvements made on AUT during the last years in order to optimize inspection philosophy and minimize the system's "Uncertainties". In addition a brand new method, RTD IWEX, is briefly described that allows the detection and sizing of weld imperfections in 3D.