Inspection of Offshore Flexible Risers With Electromagnetic and Radiographic Techniques

Abstract

Bureau Veritas, CEA and IFP studied the feasibility of on-site inspection of metal layers in the upper part of flexible risers (link between seabed and surface) used by the offshore petroleum industry. The upper part of the flexible pipe is currently the one that is the most subjected to constraints, particularly inside the stiffener. Unexpected events added to operational strain may cause cracking and breaking of these layers. Until now, no device was available to check the integrity of the various layers of the flexible risers. The authors developed electromagnetic and radioscopic techniques to inspect the upper parts of the risers. They determined the possibilities and the limits of these techniques in the detection of breaks. Inside the stiffener, at the end of the riser, the method is intrusive. Outside the stiffener, for the current length of the riser, the method is either intrusive, either non-intrusive. An internal instrumentation carrier was built for laboratory tests and an external carrier was designed for instruments positioning. This last carrier is able to move along the pipe step by step and to rotate the source and the detector around the flexible pipe on more than 360°.