Hydrogen-induced buckling degradation response of subsea defective hydrogen mixed transmission natural gas pipeline

To illustrate the hydrogen-induced buckling failure mechanism of subsea hydrogen mixed transmission natural gas pipeline, a safety assessment method with initial defects is proposed by combining experiments and numerical simulation. Considering the characteristics of material property degradation due to hydrogen-induced, the high-pressure vapor-phase in-situ hydrogen charging slow strain tensile test are carried out to study on the hydrogen-induced behavior of in-service pipelines. Non-linear buckling analysis is used to analyze the ultimate load carrying capacity under the combined bending-pressure effect based on the experimental data. Additionally, a sensitivity analysis is conducted to investigate the buckling instability behavior under different hydrogen contents, loads and defect depths. The results show that the hydrogen filled has a significant effect on the buckling instability response of the pipeline structure when the hydrogen content exceeds 25%. When the hydrogen content is 0%–25%, the buckling resistance of the pipeline only reduced by 4%–9%. When the hydrogen content increases to 50%, the buckling resistance can be reduced by about 20%. This study could provide engineering references for the design and application of hydrogen-mixed natural gas pipeline.