Mechanical Properties and Hydrogen Embrittlement Resistance of API 5L X60 Pipeline Steel in Welded and Seamless Grades
Faculty Sponsor
Dr. Patrick Ferro
ferrop@gonzaga.edu
Session Type
Poster Presentation
Research Project Abstract
API 5L X60 pipeline steel is used in pipelines such as the Keystone XL pipeline in North America. Pipeline steel is offered in seamless and welded grade, with minor chemistry differences between the two. In general, pipeline steel chemistry is engineered for performance life, fabricability, cost and resistance to hydrogen embrittlement. A section of the pipeline steel was obtained for chemical and mechanical analysis, and comparison with other alloys. To study the hydrogen embrittlement resistance, dogbone tensile bars will be extracted from the sample by milling or electrodischarge machining (EDM). The dogbones will be subjected to a range of hydrogen exposure conditions. The bars will be tensile tested to failure at different strain rates. The data will be compared with mechanical properties data for other alloys. Future investigations will include studying the effect of heat treatment on mitigation of hydrogen embrittlement-caused failure. Pipeline steel can be on the order of 36 inches in diameter and 0.625 inch nominal wall thickness. A typical installation of such a pipeline can be up to one mile in length, such as that which may be installed underneath a river. For the transportation of hydrocarbons, whether it be crude or natural gas, the entire pipeline will be constructed of an API (American Petroleum Institute) 5L X## series steel. The last two numbers X## (e.g. 60, 70, 80) correlate with the yield strength of the pipeline (so an API 5L X60, would have a 60,000 psi rating). In addition to this type of steel to stabilize the material at normal conditions, i.e. mitigate hydrogen embrittlement), an external coating is applied to the pipeline at the time of manufacturing (extruded, spiral welded). This coating is referred to as FBE (Fusion Bonded Epoxy) and is typically applied with various thickness depending on the specification. This coating is external, therefore not in direct contact with the hydrocarbon being transported. It is applied via a powder coating operation, and the coat protects the pipeline from external corrosion that it might find once buried. Additionally, for many trenchless operations (including Direct Pipe & Horizontal Directional Drilling) an additional coat is applied known as ARO (Abrasion Resistant Overcoat), which is sprayed on to a thickness depending on the specifications. This coat does not protect the pipeline from corrosion. It protects it from geotechnical formation through which it might be pulled when being installed. Nonetheless, the hydrocarbon does not come in contact with either coat because it travels inside the pipe. For this reason, the research is focused on the API 5L X## series.
Session Number
PS2
Location
HUB Multipurpose Room
Abstract Number
PS2-q
Mechanical Properties and Hydrogen Embrittlement Resistance of API 5L X60 Pipeline Steel in Welded and Seamless Grades
HUB Multipurpose Room
API 5L X60 pipeline steel is used in pipelines such as the Keystone XL pipeline in North America. Pipeline steel is offered in seamless and welded grade, with minor chemistry differences between the two. In general, pipeline steel chemistry is engineered for performance life, fabricability, cost and resistance to hydrogen embrittlement. A section of the pipeline steel was obtained for chemical and mechanical analysis, and comparison with other alloys. To study the hydrogen embrittlement resistance, dogbone tensile bars will be extracted from the sample by milling or electrodischarge machining (EDM). The dogbones will be subjected to a range of hydrogen exposure conditions. The bars will be tensile tested to failure at different strain rates. The data will be compared with mechanical properties data for other alloys. Future investigations will include studying the effect of heat treatment on mitigation of hydrogen embrittlement-caused failure. Pipeline steel can be on the order of 36 inches in diameter and 0.625 inch nominal wall thickness. A typical installation of such a pipeline can be up to one mile in length, such as that which may be installed underneath a river. For the transportation of hydrocarbons, whether it be crude or natural gas, the entire pipeline will be constructed of an API (American Petroleum Institute) 5L X## series steel. The last two numbers X## (e.g. 60, 70, 80) correlate with the yield strength of the pipeline (so an API 5L X60, would have a 60,000 psi rating). In addition to this type of steel to stabilize the material at normal conditions, i.e. mitigate hydrogen embrittlement), an external coating is applied to the pipeline at the time of manufacturing (extruded, spiral welded). This coating is referred to as FBE (Fusion Bonded Epoxy) and is typically applied with various thickness depending on the specification. This coating is external, therefore not in direct contact with the hydrocarbon being transported. It is applied via a powder coating operation, and the coat protects the pipeline from external corrosion that it might find once buried. Additionally, for many trenchless operations (including Direct Pipe & Horizontal Directional Drilling) an additional coat is applied known as ARO (Abrasion Resistant Overcoat), which is sprayed on to a thickness depending on the specifications. This coat does not protect the pipeline from corrosion. It protects it from geotechnical formation through which it might be pulled when being installed. Nonetheless, the hydrocarbon does not come in contact with either coat because it travels inside the pipe. For this reason, the research is focused on the API 5L X## series.
