Study on the lowest CO content to inhibit hydrogen embrittlement of hydrogen-blended gas transmission pipeline

Author of the article:WANG Qin1, LI Wenhao2, WU Yi1, WANG Wenchen2, XIE Ping1, LI Xiaoshuang2, ZHAO Weimin2

Author's Workplace：1. Pipe Network Group (Xinjiang) United Pipeline Co., Ltd., Urumqi, Xinjiang, 830013, China 2. College of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, Shandong, 266580, China

Key Words：Hydrogen; Pipeline; X80 steel weld; Hydrogen embrittlement; CO inhibitors

Abstract：In the process of hydrogen-blended natural gas transmission, the hydrogen embrittlement (HE) of steel pipeline is a problem to be solved in engineering safety management, and CO as a gas inhibitor can effectively prevent the HE-induced failure of the pipeline. As the dangerous area prone to hydrogen embrittlement in X80 steel pipeline, the weld was selected as the research object, nitrogen was used instead of methane, and the slow strain rate tensile tests were carried out under the environments of “N2”,“N2+H2” and “N2+H2+CO”. By adjusting the hydrogen and CO proportion, the HE index under different gas environments was calculated. Thereafter, mathematical relation model between the HE index and CO concentration was established under the different hydrogen proportion. Taking the HE index not more than 10% as the critical value of safe operation of the pipeline, the mathematical relation model between the minimum amount of CO addition and hydrogen proportion was established, so as to provide safety guidance for avoiding HE-induced failure in hydrogen-blended gas transmission pipeline.