Vallourec Qualifies Materials Wide Range of Hydrogen Applications

Hydrogen has a strong detrimental impact on the mechanical properties of steel which is known as hydrogen embrittlement. This can manifest in a decrease in ductility and fracture toughness and increases a steel’s susceptibility to fatigue causing cracks from which hydrogen can leak into the environment. Global leader in seamless pipes Vallourec has successfully carried out a first series of tests qualifying the fracture toughness resistance of a selection of steel grades for OCTG pipes, line pipes and pressure vessels in the presence of pure H2 gas.The first selection of standard and Vallourec proprietary grades tested in the presence of pure H2 gas wereGrade X65 for line pipes including the qualification of girth welds done by SerimaxGrade VM55W (55 ksi proprietary grade) for weldable OCTG pipesGrade K55 for seamless OCTG pipesGrade VM80S (80 ksi proprietary grade/L80) for seamless OCTG pipesGrade 34CrMo4 for pressure vesselsFor the qualification process of these materials, Vallourec followed the recommendations and requirements provided by the American Society of Mechanical Engineers (ASME) B31.12 option B standard for hydrogen piping and pipelines which requires all materials tested to present a hydrogen stress intensity factor threshold KIH of a minimum of 55 MPa√m. The fracture toughness evaluations performed involved exposing fatigue pre-cracked bolt-load specimens to 100 bar hydrogen gas during 1,000 hours at room temperature. K1 applied in the range of 134-176 MPa/m was used during the testing.The results of these evaluations demonstrated that all selected materials present a hydrogen stress intensity factor threshold KIH greater than 67 to 87 MPa√m, largely above the 55 MPa/m minimum required by ASME B31.12.These results prove that all tested materials are suitable for hydrogen service under 100 bar H2 gas. Furthermore, it can be argued that these materials are also suitable for higher pressures of hydrogen considering the quite limited impact of this environmental parameter beyond approximately 50 bar based on the thorough literature review performed by SANDIA laboratories2.In addition to the fracture toughness tests, Vallourec is also currently carrying out fatigue crack growth rate tests in order to provide customers with a complete understanding of the steels’ fatigue behavior to hydrogen. Other Line Pipe and OCTG grades are also currently being tested and will be progressively added to the growing portfolio of qualified Vallourec materials for hydrogen applications.These qualification results are in line with those obtained by the HystorIES project of which Vallourec is part of. Vallourec’s L80 and K55 grades were successfully tested using different methodologies in a more demanding corrosive environment in porous media. Read HystorIES’s material qualification reports here. The tests also fall within Vallourec's commitment to collaborate in establishing the guidelines for the transport of hydrogen gas in pipelines as part of DNV’s H2Pipe JIP. With the hydrogen qualification of OCTG, Line Pipe and Mechanical grades as well as of its VAM® connections, Vallourec is already able to offer a strong portfolio of solutions for a large section of the hydrogen supply chain including transport and storage in small, mid and large quantities.