In Situ Radiographic Inspection for Non-Destructive Examination of Subsea Flexible Risers

Abstract

Abstract One of the most significant subsea inspection issues has been the inability to date to obtain high resolution images of the internal layers of complex products such as flexible risers, in situ. This has significant implications for asset integrity, life, and resultant review of design. The radiographic technology, and riser integrity expertise, of CIT and BPP, have been combined with the subsea inspection design and development capabilities of Subsea 7 to develop a groundbreaking subsea NDE inspection service. This allows operators to detect a wide range of riser issues for the first time by providing high resolution images of all the various flexible riser layers (not just the outermost tensile armour). The technology being developed can unambiguously and practicably identify defects on in-service flexible risers and thereby assist resolution by intervention. This paper describes the radiographic technology used and how it is integrated into the subsea NDE tool. Technical aspects discussed compare the technology as implemented with what has otherwise been available to date. It is now possible with the radiographic technology developed to readily measure breakage of metallic layers, corrosion even when unflooded, as well as detecting loss of interlock. Fine control can also be applied to usefully view the non-metallic layers. Reference is made to Ultrasonic, Eddy Current, MAPS, and Acoustic Emission NDE techniques, and considers how these can most reasonably be used with existing and future assets.