Root cause analysis of cracking in buried X80 natural gas pipelines.

In 2021, cracks formed in an onshore buried X80 natural gas pipeline with a diameter of 1219 mm. The present study investigated the cause of this failure through environmental and operational assessment, metallurgical evaluation, mechanical testing, material testing, stress analysis, and hydrogen embrittlement (HE) sensitivity testing. The results indicated that the failure was primarily attributable to hydrogen-induced cracking (HIC). The main factors contributing to this failure were identified as excessive material hardness and strength, which resulted in a high sensitivity to HE, even within the normal cathodic protection range. In addition, the mechanical damage that occurred during the construction process resulted in the destruction of the coating, causing stress concentration on the pipe body and further facilitating HIC. • This may be the first hydrogen-related failure in a long-distance X80 pipeline. • The pipeline's excessive strength and hardness led to its failure due to hydrogen embrittlement. • Mechanical gouges led to coating damage, stress concentration, and hydrogen accumulation. • The hardness and strength of the pipeline, and the quality of construction should be strictly controlled. • Regular inspections and prompt repairs or replacements are recommended for pipeline hardness and coating conditions. [ABSTRACT FROM AUTHOR]