With an increasing number of projects involving production and use of low-carbon hydrogen, the compatibility of assets for storage and transport of hydrogen gas shall be guaranteed. Fracture toughness resistance and corrosion fatigue behavior of a selection of seamless pipes for OCTG, pipeline and pressure vessels, in pressurized H2 service, is investigated. Fracture toughness evaluations were performed via fatigue pre-cracked bolt-load specimens exposed to 100 bar hydrogen gas during 1000 h at room temperature. All materials presented hydrogen stress intensity factor thresholds KIH largely above 55 MPa.m1/2, compliant with the ASME B31.12 option B requirement that defines materials requirements for hydrogen service. Corrosion fatigue tests were performed on compact tensile specimens, also prior pre-cracking. Fatigue crack growth rate measurements were determined from 0.01 to 30 Hz and load ratios at 0.1 or 0.9 for covering applications susceptible to present very different internal pressure variations during service life. A focus is given on the influence of load ratios on threshold ΔK for initiating fatigue in presence of hydrogen. Data provided can be used for building Failure Assessment Diagram, decisive tool for predicting the safe domain of usage of structures.
Hydrogen gas is called to play a key role in the energy transition and initiatives needed for a decarbonization of the economy. Initially, assets for energy storage and transport were developed and qualified for the purpose of the oil and gas industry, especially natural gas. Repurposing of existing assets for the use of hydrogen gas, or creation of new dedicated hydrogen transport and storage infrastructure, is a great challenge for future hydrogen projects. It includes the qualification of steel materials under hydrogen gas environment.
There are still only few international standards dedicated to the material selection for hydrogen gas environment. European Industrial Gases Association (EIGA) proposes two documents: IGC Doc 121/14 and IGC Doc 100/03/E for hydrogen pipeline systems and hydrogen cylinders and transport vessels, respectively. For the former, EIGA imposes to limit steel grade to X52 or below, 22 HRC maximum and a hoop stress not more than 30% of Specified Minimum Yield Strength (SMYS). For IGC Doc 100/03/E, materials must be a quenched and tempered 34CrMo4 presenting Ultimate Tensile Strength (UTS) less than 950 MPa and a ratio YS/UTS less than 0.9. American Society of Mechanical Engineers (ASME) proposes design code B31.12 for hydrogen piping and pipelines. With option A, steel grades having SMYS 65 ksi can be used with a severe penalty on the maximum acceptable internal pressure. In order to limit this penalty, option B can be used, which guarantees pipeline integrity in service by the combination of Fracture Toughness (FT) and Fatigue Crack Growth Rate (FCGR) tests to assess the maximum number of cycles before reaching the maximum acceptable crack length.
