Effect of glass fiber composite structure on external crack arrest performance of CO₂ pipeline

Objective Carbon Capture, Utilization, and Storage (CCUS) is regarded as a key technology essential for China to achieve its “carbon peaking and carbon neutrality” objectives. CO₂ pipeline transportation is considered an important element in realizing large-scale CCUS. However, due to various defects in CO₂ pipelines, the unique decompression characteristics of CO₂, and the influence of internal pipeline pressure, these pipelines face significantly elevated hazards of defects evolving into initial cracks and leading to ductile propagation, which poses a serious threat to the safety of pipeline transportation. Methods Aimed at achieving effective crack arrest for CO₂ pipelines, a model of external crack arrest structures made from glass fiber composites was developed using the finite element software ANSYS. The reliability of this model was verified using the J-integral theory formula developed by the Electric Power Research Institute (EPRI) and the stress distribution theory formula. Subsequently, the effects of various factors on the crack arrest performance of these external structures were analyzed, including paving angle, paving thickness, paving length, pipe diameter-to-thickness ratio, and crack size. Additionally, the developed model was evaluated for Pipeline L21, which is intended for the transportation of 400×10⁴ t/a of supercritical CO₂ in the Yanchang Oilfield. Results The external crack arrest structures made from glass fiber composites were identified as effective in transferring and bearing stress on the pipeline, thereby mitigating the risk of ductile fracture. Paving thickness, paving length, pipe diameter-to-thickness ratio, and crack size were found to be positively correlated with crack arrest performance, while an optimal paving angle was consistently observed. Among various factors contributing to crack arrest performance, paving thickness had the greatest effect, whereas paving angle had the least impact. The optimal configurations for performance included a paving thickness equal to the pipe wall thickness, a paving length of 0.8 times the outer diameter of the pipe, and a paving angle of 60°. Conclusion Paving external crack arrest structures with a thickness of 12 mm and a length of 326 mm can effectively prevent ductile fracture in Pipeline L21. These research findings provide a theoretical basis and practical examples for the design of external crack arrest structures.