Abstract
Future energy needs along with efforts to combat climate change worldwide will result in the need for a sufficient network of transmission pipeline systems. This network of transmission pipelines must be designed to be able to move various forms of energy consisting of natural gas, high pressure gaseous hydrogen, blended high pressure hydrogen/natural gas along with carbon capture of CO2 both safely and economically. Safely means optimum through thickness crack arrest characteristics which comes from the ductility of the through thickness microstructure. Economically means higher operating pressures, potentially up to 10–13.8 MPa (1500–2000 psi) in larger diameters and thicker pipe walls. Recent laboratory and industrial projects have been done to better understand how to design an optimum alloy and process for an improved through thickness microstructure, grain size and homogeneity. This has resulted in gains in fracture toughness, low temperature ductility performance in average values or stability/standard deviation or both. In addition, testing in high pressure gaseous hydrogen up to 21 MPa (3000 psi) has shown an improvement and stability of fracture toughness between 5.5 MPa (800 psi) and 21 MPa (3000 psi) along with an observed improved fatigue crack growth rate, especially in the typical operating pipeline stress intensity factor (ΔK, MPa-m0.5) range of 8–12 MPa-m0.5. This paper will introduce the recent laboratory and industrial projects results along with examples of recommendations for optimum alloy/processing design for improved overall ductility performance for these critical future pipeline applications.
