TomX: High-Energy Tomographic X-Ray for In-Service Inspection of Flexible Pipeline Systems

Abstract

The applications of flexible pipes are increasing, and so is the demand for good inspection methods and integrity assessment tools, both from Operators and Authorities. Leakage or damage to the pipe on topsides could lead to an increased safety risk, uncontrolled shutdowns, longer system downtime and major financial loss. For several years, the Norwegian oil company, Statoil, has investigated the feasibility of developing x-ray computed tomography (CT) systems for on-site inspection of flexible pipelines. Special consideration has been given to the end fitting area on topsides. The development led to the foundation of the company TomX AS in 2001. With contributions from Statoil, Aker Kvaerner and NUI, the company has focused on studies and tests to confirm the feasibility of CT technology for inspection of flexible pipes. Much effort has been concentrated on proving that it is possible to get high quality CT images of flexible pipes and end fittings on topsides. The detection criteria are defined as flaws in the pressure barrier, as defined by the Statoil R&D group. The flaw size gives an estimate of the remaining lifetime of the flexible pipes. Until now, no non-destructive, non-intrusive inspection method has been able to inspect the pressure barrier. Tests with computed tomography show that this can become a unique way of getting reliable information about all layers in a flexible pipe, including the pressure barrier. Results from these tests are presented and discussed in this paper. Furthermore, possible analysis methods are introduced. ACT inspection tool is made up of a high-energy x-ray source, a detector array and a highly accurate mechanical system. Limited access on offshore installations, high demands for accuracy and radiation safety put strict requirements on the design of the tool. Prototype design for offshore inspection and inspection in conjunction with the Factory Acceptance Test (FAT) of the flexible pipe end fitting is presented and operational challenges are assessed.