Abstract
In recent years, many synthetic natural gas demonstration projects have been put into operation all over the world, and hydrogen is usually contained in synthetic natural gas. X80 is the most commonly used high-grade pipeline steel in the construction of natural gas pipelines. The compatibility between high-grade pipeline steel and hydrogen directly affects safety and reliability of long-distance pipelines. Therefore, in order to study the effect of hydrogen content on fatigue properties of high-grade pipeline steel, fatigue specimens were taken from base metal, spiral welds, and girth weld of submerged arc spiral welded pipes, respectively. Specifically, the total pressure was 12 MPa and hydrogen content was from 0 to 5vol%. Experimental results indicate that the hydrogen significantly increases the fatigue crack growth rate for both base metal, spiral weld, and heat-affected zone of X80 pipeline steel for about ten times compared with reference environment nitrogen, hydrogen would greatly reduce the fatigue life of the X80 pipeline steel, and the fatigue lifetime would decrease with the increase in hydrogen volume fraction. In order to ensure the safe operation of SNG pipeline, the hydrogen content should be controlled as low as possible.
Highlights
With the substantial increase in energy demand, many countries have increased the exploitation of oil and gas resources to meet the demands of the market
This study studied the base metal and spiral weld and girth weld [8, 9]
It can be concluded that hydrogen greatly reduces the fatigue life of the X80 base metal, and the fatigue life would decrease with the increase in hydrogen volume fraction
Summary
With the substantial increase in energy demand, many countries have increased the exploitation of oil and gas resources to meet the demands of the market. China has planned some large-scale coal-gasification projects, and pipelines such as Xinjiang-Guangdong-Zhejiang synthetic natural gas pipeline project have been constructed to transport SNG. In order to prevent pipeline failure caused by hydrogen and ensure the service safety of synthetic natural gas (SNG) transmission, some scholars have begun to study the effect of hydrogen on the mechanical properties of pipeline steel. The research on girth weld is relatively limited, and in recent years, girth weld is the most vulnerable part of failure in the pipeline system due to structure and other factors. In this regard, this study studied the base metal and spiral weld and girth weld [8, 9]. The composition and microstructure of X80 pipeline steel have changed greatly. erefore, the most typical X80 pipeline steel for pipeline construction is adopted as the research object in this paper
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