A riser forms the connection between the topside of an offshore platform and a pipeline on the sea bed. Increasingly, offshore operators are committed to protect the environment. Pipeline pigging and riser inspection will assist in determining the integrity of the line and the riser, in particular. In this article, a new approach for a full-coverage ultrasonic inspection of the riser only is described, based on the application of a compact umbilical-cable, tether-operated, tool. This requires the riser to be shutdown and filled with a liquid. The inspection tool providesan on-line presentation of results, for immediate evaluation. The system uses straight-beam ultrasonic sensors for a general corrosion survey of the pipe material, and the TOFD (time of flight diffraction) technique for additional inspection of the circumferential weld area.
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