PSI - Issue 81

Olha Zvirko et al. / Procedia Structural Integrity 81 (2026) 41–46

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Table 1 shows the results of the SIF calculations for the deepest point of the crack front on the inner surface of the pipe.

Table 1. SIF calculation results ( MPa √m ) for the deepest point of the surface semi-elliptical crack front Pressure P, MPa Depth a, mm Longitudinal direction Circumferential direction a/c = 1/3 a/c = 2/3 a/c = 1/3 a/c = 2/3 3.5 1 9.95 8.12 4.99 4.05 2 14.18 11.48 7.12 5.72 7.5 1 21.32 17.40 10.69 8.68 2 30.38 24.60 15.26 12.25

The calculated SIF values (Table 1) indicate that under the given loading conditions and crack geometry, they do not reach the critical value of 55 MPa·√m. This indicates the possibility of safe further operation of the pipe even with a crack length of 2 mm and a maximum pressure of 7.5 MPa. For the crack parameters for which the highest SIF was obtained (for P = 7.5 MPa, a = 2 mm and a/c = 1/3), SIF was additionally calculated for a = 3 mm, 38.29 MPa·√m. Therefore, it can be assumed that the SIF value for a deeper crack may be close to the limit, and the operation of a pipe with such a crack may be problematic. The analysis performed should be considered as the first stage in substantiating the safe operation of existing gas pipelines in the context of hydrogen transportation. 4. Conclusions Long-term operated pipeline steel is sensitive to hydrogen embrittlement in terms of fracture toughness, which is especially evident at low loading rates of specimens and high hydrogenation intensity. A criterion for the limit state of steels in terms of fracture toughness is proposed, determined experimentally using the J -integral method, accounting for hydrogenation conditions, gas pressure in the pipe, the presence of crack-like defects, and operational degradation. It is shown that, for the 17H1S pipeline steel, after long-term service, the fracture toughness can decrease to a limit value under certain hydrogenation regimes and low loading rates, indicating a loss of its suitability for further operation, particularly in conditions of hydrogen transportation. Calculations of the stress intensity factor for semi-elliptical cracks in a pipe demonstrated that, under the considered loading conditions and crack geometries, the SIF values do not reach the limit one, indicating the possibility of safe operation of pipes with defects up to 2 mm deep at pressures up to 7.5 MPa. The proposed approach can be used to assess the serviceability of steels of gas transit pipelines at their reprofiling for hydrogen transportation, as well as to develop criteria for their safe operation, taking into account the operational degradation of steels and the influence of hydrogen. Acknowledgements The research was carried out with partial financial support from the National Academy of Sciences of Ukraine under R&D project (Registration No. 0124U0000911) and the National Research Foundation of Ukraine under Project No 2022.01/0099. References API 579 - 1 / ASME FFS - 1, Fitness - For - Service. June, 2016. ASME B31.12. Hydrogen Piping & Pipelines. Digital Book. ASME, 2023. 268 р. ASTM E1820. Standard Test Method for Measurement of Fracture Toughness, 2018. Boukortt, H., Amara, M., Hadj Meliani, M., Bouledroua, O., Muthanna, B.G.N., Suleiman, R.K., Sorour, A.A., Pluvinage, G., 2018. Hydrogen embrittlement effect on the structural integrity of API 5L X52 steel pipeline. International Journal of Hydrogen Energy 43(42), 19615 – 19624. Campari, A., Ustolin, F., Alvaro, A., Paltrinieri, N., 2023. A review on hydrogen embrittlement and risk - based inspection of hydrogen technologies, International Journal of Hydrogen Energy 48(90), 35316 – 35346. Cao, J., 2024. Effect of hydrogen embrittlement on the safety assessment of low - strength hydrogen transmission pipeline. Engineering Failure Analysis 156, 107787. Chowdhury, M.F.W., Tapia - Bastidas, C.V., Hoschke, J., Venezuela, J., Atrens, A., 2025. A review of influence of hydrogen on fracture toughness and mechanical properties of gas transmission pipeline steels. International Journal of Hydrogen Energy 102, 181 – 221. Depover, T., Pérez Escobar, D., Wallaert, E., Zermout, Z., Verbeken, K., 2014. Effect of hydrogen charging on the mechanical properties of advanced high strength steels. International Journal of Hydrogen Energy 39(9), 4647 – 4656. Dubyk , Y., Seliverstova , I., 2019. Assessment of dents for gas pipelines. Procedia Structural Integrity, 18, 622 – 629. Hoschke, J., Chowdhury, M. F. W., Venezuela, J., Atrens, A., 2023. A review of hydrogen embrittlement in gas transmission pipeline steels. Corrosion Reviews 41(3), 277 – 317. Hrabovskyy, R., Kryzhanivskyy, Y., Tuts, O., Mandruk, O., Tyrlych, V., Artym, V., Sapuzhak, Y., 2024. Impact of long - term operation on reliability and durability of natural gas pipeline: potential environmental consequences of accidents. Procedia Structural Integrity 59, 112 – 119. Jack, T.A., Webb, M.A., Rahman, K.M.M., Fazeli, F., Szpunar, J., 2025. Hydrogen uptake and embrittlement behavior in pipeline steels: Insights from slow strain rate testing and synchrotron micro - CT imaging. Engineering Failure Analysis 172, 109419. Kappes, M. A., Perez, T., 2023. Hydrogen blending in existing natural gas transmission pipelines: a review of hydrogen embrittlement, governing codes, and life prediction methods. Corrosion Reviews 41(3), 319 – 347.