Applying Case 1: Pipeline testing Lack of Fusion in the Girth Weld of a Newly Constructed Long-Distance Natural Gas Transmission Pipeline Background:
An X70 long-distance transmission pipeline, DN800, wall thickness 16 mm. The girth welds were inspected by PAUT and TOFD. Method:
Phased Array Ultrasonic Testing (PAUT) and Time-of-Flight Diffraction (TOFD), supplemented by random Radiographic Testing (RT). Findings:
Root lack of fusion (root LOF) was detected in one girth weld. The defect length was 12 mm, and the depth was 2–3 mm. The defect height measured by TOFD was 1.8 mm. The indication was not clearly visible on the RT film. Conclusion:
The weld was judged unacceptable in accordance with API 1104. Disposition:
After repair, the weld passed re-inspection by PAUT and TOFD. Subsequent welds made by the same welder were subjected to additional inspection.
|
