Non destructive testing of the internal weld of large diameter seamless steel pipe: because the pipe belongs to super large steel pipe in the water supply project, especially the steel pipe with a thickness of t=30 mm is used as a pipe bridge, which not only bears the internal water pressure, but also bears the bending moment formed by the dead weight of the steel pipe and the water body, so the requirements for welding quality are very high.
For the t=30mm thick steel pipe used for large-diameter seamless steel pipe bridge, its longitudinal seam and circumferential seam belong to Class I weld, and 100% X-ray radiography and 100% ultrasonic flaw detection are required; For buried steel pipes with a thickness of t=24mm, the longitudinal joints belong to Class I welding, and 20% X-ray examination and 50% ultrasonic flaw detection shall be carried out.