Abstract
The safe hydrogen transport requires an evaluation of existing natural gas pipelines to ensure the integ-rity and reliability of the infrastructure. Material degradation due to hydrogen embrittlement must be considered when assessing the compatibility of pipeline steel in contact with hydrogen. The aim of this work is to study the effect of hydrogen on the fracture mechanical properties and to evaluate the exist-ing natural gas pipeline for repurposing to the transport of hydrogen using a fracture mechanics ap-proach. The paper is divided into experimental and analytical parts. The first section presents the results of experimental investigations carried out on samples taken from two in-operation industrial pipelines (steel grade X70) used to transport natural gas. Fracture mechanics tests were carried out on both base materials and weld metals under monotonic and cyclic loading in both air and hydrogen environments. The second part addresses the question of whether a representative natural gas pipeline can be safely used for hydrogen transport. The analyses were carried out for a hypothetical surface crack axially ori-ented on the inside of the pipe. The crack was subjected to gas pressure fluctuations recorded over three years of operation of the natural gas pipeline. Parameter studies show the effect of fracture me-chanical properties and residual stresses on the service life of the pipeline.
