In service monitoring of flexible risers using submarine X-ray computed tomography

Fouchard, Alexandre; CyXplus; France

Decroux, A.; CyXplus, Research and Development; France
Fouchard, A.; CyXplus, Research and Development; France
Nicolas, Y.; TechnipFMC; France
Philippe, J-R.; CyXplus, Research and Development; France

ID: ECNDT-0131-2018
Session: CT-Applications 4
Room: G3
Date: 2018-06-13
Time: 15:20 - 15:40

The mastering of the whole life cycle of oilfields is a major challenge for oil companies. To enable predictive and remedial maintenance for offshore installations, in situ nondestructive techniques are required. TechnipFMC and CyXplus have then undergone developments to provide an in-service riser inspection system (IRIS). While the overall tele-operated machine will feature ultrasound, electromagnetic and X-ray inspection capabilities, the focus in this study will be put on the latter.
A dedicated X-ray acquisition chain was first set up in ambient air to benchmark the imaging potential. This included a linear accelerator able to supply high energy X-rays to penetrate double-walled metallic samples. A specific rotation plate was designed to sustain 5 ton weights and deliver mechanical positioning precisions compatible with tomography requirements; its programmable logic controller interfaced with a flat panel detector, making the platform quite versatile. Numerical simulations and experimental benchmarks were conducted on representative samples presenting voluntarily induced flaws within the different inner layers of the pipe structure. Specific developments were also undertaken in terms of signal processing, to provide a multi-resolution display, automatic defect recognition and classification.
Reference tomographies were obtained, enabling to compare and refine numerical models in terms of signal to noise ratio and contrast to noise ratio. These figures of merit were used to optimize the acquisition conditions, e.g. geometry, emission and detector parameters. Signal processing algorithms enabled to correctly detect, localize and quantify flaws. These results allowed to study the adaptation of the acquisition material to the in situ operational requirements, e.g. size, pressure and remote control.
Submarine computed tomography will be used to confirm the anomalies detected by electromagnetic or ultrasound. It will also assess the innermost layers of the pipe structure, providing an unparalleled means of in-situ inspection. The first working prototype including X-ray tomography is expected early 2019.