Session: DA-21-01 Design and Analysis of Hydrogen Pressure Equipment - 1

Paper Number: 101664

101664 - Numerical Analysis of Hydrogen Diffusion and Distribution at Corrosion Defect on Aged Pipelines for Hydrogen Service 

Repurposing existing natural gas pipelines for hydrogen transport is continuously attracting a wide and strong curiosity and enthusiasm. However, the corrosion defects present on these aged pipelines can affect hydrogen (H) atom accumulation, potentially causing hydrogen embrittlement occurrence due to a detrimental effect of hydrogen on the degeneration of pipeline steel. It is very critical to assess the hydrogen concentration when converting the existing pipelines for hydrogen service. In this work, a finite element-based model was developed by coupling solid mechanics and H atom diffusion fields to simulate and investigate the H atom distribution in interstitial sites and in trapping sites, which are assumed to be two kinds of H distribution locations, at a corrosion defect on steel pipe under applied longitudinal tensile strain. The tensile strain applied on the pipe causes local stress (both Mises stress and hydrostatic stress) and equivalent plastic strain concentrations at the corrosion defect, changing the H atom diffusion and distribution. In the absence of the tensile strain, the H atoms, once entering the interior of pipe, diffuse uniformly into the steel pipe along the radial direction driven by a concentration gradient. When a tensile strain is applied on the pipe, the H atom diffusion is also driven by hydrostatic stress. The maximum H atom concentrations exceed the initial boundary concentration of H atoms entering the steel pipe, indicating the H atom accumulation occurring at the corrosion defect. The applied tensile strain also affects the location where the maximum H atom concentration is recorded. And the H distributions and concentrations in interstitial sites and trapping sites are remarkably different. The proposed model can be used to determine whether the local H atom concentration exceeds a threshold value under given stress conditions and help pipeline operators evaluate and predict the potential occurrence of pipeline HE and the cracking locations.

Presenting Author: Shiwen Guo China University of Petroleum-Beijing

Presenting Author Biography: Shiwen Guo, Ph.D, July 6th 1995, Department of Safety and Ocean, China University of Petroleum-Beijing

Authors:

Shiwen Guo China University of Petroleum-Beijing
Shaohua Dong China University of Petroleum-Beijing
Frank Cheng University of Calgary