Speaker
Description
The repurposing of existing subsea natural gas pipelines for hydrogen transport may reduce infrastructure costs in the low-carbon energy transition, but hydrogen exposure can degrade pipeline steels through embrittlement and reduced fatigue resistance. This study assesses the structural integrity and remaining fatigue life of a representative subsea pipeline converted to hydrogen service, focusing on free-spanning sections subjected to cyclic hydrodynamic loading. A two-stage numerical framework was applied. A global OrcaFlex model of a 29 km route identified 43 free spans, with a maximum unsupported length of 30 m. This critical span was then analysed in ANSYS Mechanical using static, modal and harmonic response analyses. At an estimated vortex-shedding frequency of 0.46 Hz, the nominal axial stress range was 15.52 MPa. Fatigue assessment using the stress-life approach showed a reduction in life from 309 years for the natural gas baseline to 94 years using DNV-RP-C203 Curve F and 26 years using a modified BS7608:2015 F-curve. After 30 years of prior operation and applying a design fatigue factor of 6, remaining hydrogen service life decreased to 14 and 4 years, respectively. Pressure derating and free-span correction significantly improved fatigue life, supporting hydrogen repurposing under controlled integrity-management conditions.
| Topic Area | Fatigue, Corrosion and Structural Integrity of Engineering Structures and Mechanical Systems |
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