Assessing the Use of Composite Materials in Reinforcing Offshore Risers and Pipelines

Abstract

Composite systems are a generally-accepted method for repairing corroded and mechanically-damaged onshore pipelines. The pipeline industry has arrived at this point after more than 15 years of research and investigation. Because the primary method of loading for onshore pipelines is in the circumferential direction due to internal pressure, most composite systems have been designed and developed to provide hoop strength reinforcement. On the other hand, offshore pipes (especially risers), unlike onshore pipelines, can experience significant tension and bending loads. As a result, there is a need to evaluate the current state of the art in terms of assessing the use of composite materials in repairing offshore pipelines and risers.The paper presents findings from a joint industry effort involving the Minerals Management Service, the Offshore Technology Research Center at Texas A&M University, Stress Engineering Services, Inc., and several composite repair manufacturers was undertaken to assess the state of the art using full-scale testing methods. Loads typical for offshore risers were used in the test program that integrated internal pressure, tension, and bending loads. This program is the first of its kind and likely to contribute significantly to the future of offshore riser repairs. It is anticipated that the findings of this program will foster future investigations involving operators by integrating their insights regarding the need for composite repair based on emerging technology. PROGRAM OVERVIEWThe program incorporated 8.625-inch x 0.406-inch, Grade X46 pipe test samples that were prepared with simulated corrosion by machining. The program destructively tested a total of 12 separate samples with three being repaired by each of the four manufacturers. The tests included a burst test (increasing pressure to failure), a tension-to-failure test (pressure held constant with increasing axial tension loads to failure), and a four-point bend test (pressure and tension held constant with increasing bending loads to achieve significant yielding in steel pipe) for each of the repair systems.The four-team Joint Industry Project (JIP) was formed to assess the current state of the art. Each repair system was evaluated considering a combination of pressure, tension, and bending loads. To maintain anonymity, each company's product was assigned a letter reference designation as noted below.

Marine Application of Fiber Reinforced Composites: A Review

“…The pre-cured layer technique consists of using pre-impregnated composites avoiding issues attributable to an underwater resin cure in a restricted and not easily accessible space. This method is mainly applied in case of damage localized on straight pipe sections [24,25].…”

“…Reinforcement architecture is not strictly longitudinal. Fibers are aligned in both longitudinal and circumferential directions, following a helix pattern, over the entire length of the riser [25,28,32].…”

Finite element analysis (FEA) modelling of fiber-reinforced polymer (FRP) repair in offshore risers

“…For the past 10 years, the use of composite materials in repairing onshore pipelines has been investigated extensively and improved and is now generally accepted as one of the principal repair techniques (Alexander, 2006;Patrick, 2004). However, the application of this technology in repairing offshore risers has not been validated technically.…”

Reinforcing Large Diameter Elbows Using Composite Materials Subjected to Extreme Bending and Internal Pressure Loading

“…Design and assessment of a carbon-epoxy system used to reinforce offshore risers subjected to combined loads using finite element modeling and full-scale destructive testing [12][13][14] The research programs in the above list served to provide valuable information and insights on the performance of composite repair technologies. The cumulative knowledge accumulated regarding the performance of composite repairs was important in completing the reported work and designing the system used in service.…”