Hydrogen Environment Research Articles

Materials aspects associated with the addition of up to 20 mol% hydrogen into an existing natural gas distribution network

The introduction of hydrogen into the UK natural gas main has been reviewed in terms of how materials within the gas distribution network may be affected by contact with up to 80% Natural Gas (NG)/20 mol% hydrogen blend at up to 2 barg. A range of metallic, polymeric and elastomeric materials in the gas distribution network (GDN) were assessed via a combination of literature review and targeted practical test programmes.The work considered:• The effect of hydrogen on metallic materials identified in the network.• The effect of hydrogen on polymeric materials identified in the network.• The effect of hydrogen exposure on polyethylene pipeline joining and repair techniques (squeeze-off, and socket and saddle electrofusion joints)The experimental work involved soaking materials, under pressure conditions representative of the network, in 100% hydrogen, 20% hydrogen in methane, and 100% methane. For the metal samples, the test programme involved the assessment of hydrogen uptake on the tensile properties. For the polyethylene samples, the test programme looked at the assessment of possible hydrogen absorption/desorption and its effect on electrofusion jointing.The trials concluded that the majority of metallic materials showed no significant deterioration in mechanical (tensile) properties when stored in hydrogen environments compared to those stored in analogous methane or blended gas atmospheres up to 2 barg. Polymeric materials showed no deterioration to efficiency of squeeze-off or collar electrofusion in socket or shoulder orientations following soaking in hydrogen, methane or hydrogen blends.

Macro-Micro Analysis on 2-Layer Semiautomatic MIG Welding of AA5052 Material Using ER5356 Electrode

Lightweight structures have widely been used due to their weight saving. Aluminum alloys are among the alternative for their material, and they are mostly manufactured by employing welding process using the same filler material as the base metal. Aluminum welding process can be conducted employing 2-layer semiautomatic MIG when the thickness of the plate is no more than 5 mm. Porosity in aluminum alloy welding is considerably difficult to avoid due to hydrogen and oxygen environment. Macro-micro analyses on 2-layer semiautomatic MIG welding of AA5052 material using ER5356 electrode have been carried out. A pair of AA5052 plates of 400 mm x 75 mm x 5 mm were clamped at three points of one side and welded using 2-layer semiautomatic MIG welding using ER5356 filler such that angular distortion can happen. Welding speed of 6, 7, and 8 mm/s using electrical voltage of 23 Volt, current of 130 Ampere, filler diameter of 0.8 mm, and shielded using argon gas. After completion of the welding, angular distortion was measured using dial indicator possessing accuracy of 0.01 mm. Welding result was micro-Vickers (VHN0.1) hardness, tension and Charpy impact, as well as micro structure using OM and SEM-EDS. The highest tensile strength was found at welding speed of 7 mm/s, angular distortion of 6.780, average VHN0.1 of the BM, HAZ, and WM of 47.82, 49.14, and 51.75, respectively. Tensile strength of 156.5 MPa and joint efficiency of 70%, BM failure strain of 17%, Charpy impact of 0.26 J/mm2. SEM-EDX at spot shows that the amount of Mg is not significant for being Al2Mg3 precipitate such that Vickers hardness distribution do not show any difference among BM, HAZ, and WM.

Tip hydrogen sensor based on liquid-filled in-fiber Fabry–Pérot interferometer with Pt-loaded WO3 coating

A probe optical fiber hydrogen sensor based on an in-fiber Fabry–Pérot interferometer (FPI) is proposed and experimentally demonstrated. The interferometer consists of a micro-cavity which is filled with thermosensitive liquid and lateral surface coated with hydrogen-sensitive material of Pt-loaded WO3. When the sensor is exposed to the hydrogen environment, the refractive index of the liquid in the cavity changes, and then the reflection spectrum of the FPI shifts due to the exothermal reactions between the hydrogen and WO3 in air with the presence of oxygen and the help of catalyst Pt. By detecting the wavelength shift, the hydrogen concentration can be measured accurately. Experimental results show that the proposed sensor has a high hydrogen sensitivity within a range from 0 to 4.0% (vol.%) and a short response time. Moreover, it exhibits many distinct advantages, such as a tip structure with compact size (<100 μm in total dimension), good repeatability and selectivity to hydrogen and immunity to humidity. All these features reveal that the proposed sensor is promising in the fields of hydrogen leaks or concentration measurement in a narrow space.

Hydrogen embrittlement in ferritic steels.

Hydrogen will be a crucial pillar in the clean-energy foundation, and therefore, the development of safe and cost-effective storage and transportation methods is essential to its success. One of the key challenges in the development of such storage and transportation methods is related to the interaction of hydrogen with structural materials. Despite extensive work, there are significant questions related to the hydrogen embrittlement of ferritic steels due to challenges associated with these steels, coupled with the difficulties with gauging the hydrogen content in all materials. Recent advancements in experimental tools and multi-scale modeling are starting to provide insight into the embrittlement process. This review focuses on a subset of the recent developments, with an emphasis on how new methods have improved our understanding of the structure-property-performance relationships of ferritic steels subjected to mechanical loading in a hydrogen environment. The structure of ferritic steels in the presence of hydrogen is described in terms of the sorption and dissociation processes, the diffusion through the lattice and grain boundaries, and the hydrogen-steel interactions. The properties of ferritic steels subjected to mechanical loading in hydrogen are also investigated; the effects of test conditions and hydrogen pressure on the tensile, fracture, and fatigue properties of base metal and welds are highlighted. The performance of steels in hydrogen is then explored via a comprehensive analysis of the various embrittlement mechanisms. Finally, recent insights from in situ and high-resolution experiments are presented and future studies are proposed to address challenges related to embrittlement in ferritic steels.

Effect of microstructural and environmental variables on ductility of austenitic stainless steels

Austenitic stainless steels are used extensively in harsh environments, including for high-pressure gaseous hydrogen service. However, the tensile ductility of this class of materials is very sensitive to materials and environmental variables. While tensile ductility is generally insufficient to qualify a material for hydrogen service, ductility is an effective tool to explore microstructural and environmental variables and their effects on hydrogen susceptibility, to inform understanding of the mechanisms of hydrogen effects in metals, and to provide insight to microstructural variables that may improve relative performance. In this study, hydrogen precharging was used to simulate high-pressure hydrogen environments to evaluate hydrogen effects on tensile properties. Several austenitic stainless steels were considered, including both metastable and stable alloys. Room temperature and subambient temperature tensile properties were evaluated with three different internal hydrogen contents for type 304L and 316L austenitic stainless steels and one hydrogen content for XM-11. Significant ductility loss was observed for both metastable and stable alloys, suggesting the stability of the austenitic phase is not sufficient to characterize the effects of hydrogen. Internal hydrogen does influence the character of deformation, which drives local damage accumulation and ultimately fracture for both metastable and stable alloys. While a quantitative description of hydrogen-assisted fracture in austenitic stainless steels remains elusive, these observations underscore the importance of the hydrogen-defect interactions and the accumulation of damage at deformation length scales.

A Novel Interdigitated Electrode Design and Methodology for the Measurement of Ionic Conductivity of Ionomer Thin Film on Carbon Substrate

In this work, we introduce a new design of the interdigitated electrode (IDE) for the measurement of conductivity of ionomer thin film on the planar carbon surface, which is relevant to many electrochemical systems including fuel cells. The design is an advancement over commonly used SiO2 substrate based IDE, previously employed for Nafion thin film conductivities. Electrochemical impedance spectroscopy technique was applied to measure the conductivity of 55 nm thick Nafion film on carbon surface. Through complementary modeling work using equivalent circuit, we identify that the competition between the double layer capacitances at ionomer/carbon and ionomer/electrode interfaces can mask the conventionally observed high-to-medium impedance arc observed for Nafion films on SiO2 substrate. This problem can be circumvented by using electrochemically active Pt electrode in hydrogen environment. Hence, this systematic study describes a method to determine the thin film conductivity on carbon substrate.

Enhanced solar light driven hydrogen generation and environment remediation through Nd incorporated ZnIn2S4

Visible-light-driven hydrogen production is a promising pathway to realize efficient solar energy utilization. Here, Nd3+ incorporated ZnIn2S4 (Nd-ZIS) was synthesized via facile one step hydrothermal method. Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS) confirm the successful incorporation of Nd3+ in ZnIn2S4. Optical studies reveal the reduction of effective bandgap from 2.7 eV to 2.54 eV upon incorporation of Nd3+ with improved charge carrier life time of 3.12 ns. Electronic properties of ZIS and Nd-ZIS were investigated from first principle calculations. An attempt to improve photocatalytic activity of ZIS by modification with Nd3+ ions resulted in degradation of organic pollutant up to 98% under natural sunlight and decrease in life time of trap states up to a nominal value of 200 ms (as evident from photoelectrochemical measurements). The mechanism behind enhancement of photocatalytic activity of ZIS post Nd3+ integration has been proposed. Nd-ZIS was also utilized for water splitting activity exhibiting a considerable H2 generation ∼3415 μmol g−1. To the best of our knowledge, activity of Nd3+ incorporated ZIS has been explored for the first time in present work. It is believed that an in-depth understanding of photoactivity of ZIS would be significantly important for designing materials with desired photocatalytic performance in future.

An investigation of hydrogen embrittlement of 12Cr2Mo1R(H) steel by slow strain rate tests and first-principles calculation

Purpose With excellent mechanic properties and hydrogen embrittlement (HE) resistance, 12Cr2Mo1R(H) steel is suitable to make hot-wall hydrogenation reactors. However, longtime exposure to a harsh environment of high-pressure hydrogen at medium temperature in practical application would still induce severe hydrogen uptake and eventually damage the mechanical properties of the steel. The study aims to evaluate the HE resistance of the steel under different tensile strain rates after hydrogen charging and analyze the hydrogen effect from atomic level. Design/methodology/approach This research studied the HE properties of 12Cr2Mo1R(H) steel by slow strain rate tests. Meanwhile, the effect of hydrogen on the structures and the mechanical properties of the simplified models of the steel was also investigated by first-principle calculations. Findings Experimental results showed that after hydrogen pre-charging in this work, hydrogen had little effect on the microstructure of the steel. The elongations and reduction of cross-sectional area of the samples reduced a lot, by contrast, the yield and tensile strengths changed slightly. The 12Cr2Mo1R(H) steel was not very susceptible to HE with a maximum embrittlement index of about 20.00%. First principles calculation results showed that after H dissolution, lattice distortion occurred and interstitial H atoms would preferentially occupy the tetrahedral interstitial site in bcc-Fe crystal and increase the stability of the supercells. With the increase of H atoms added into the simplified model, the steel still possessed a good ductility and toughness at a low hydrogen concentration, while the material would become brittle as the concentration of hydrogen continued to increase. Originality/value These finds can provide valuable information for subsequent HE studies on this steel.

Evolution of Welding Residual Stresses within Cladding and Substrate during Electroslag Strip Cladding.

Hydrogenation reactors are important oil-refining equipment that operate in high-temperature and high-pressure hydrogen environments and are commonly composed of 2.25Cr–1Mo–0.25V steel. For a hydrogenation reactor with a plate-welding structure, the processes and effects of welding residual stress (WRS) are very complicated due to the complexity of the welding structure. These complex welding residual stress distributions affect the service life of the equipment. This study investigates the evolution of welding residual stress during weld-overlay cladding for hydrogenation reactors using the finite element method (FEM). A blind hole method is applied to verify the proposed model. Unlike the classical model, WRS distribution in a cladding/substrate system in this study was found to be divided into three regions: the cladding layer, the stress-affected layer (SAL), and the substrate in this study. The SAL is defined as region coupling affected by the stresses of the cladding layer and substrate at the same time. The evolution of residual stress in these three regions was thoroughly analyzed in three steps with respect to the plastic-strain state of the SAL. Residual stress was rapidly generated in Stage 1, reaching about −440 MPa compression stress in the SAL region at the end of this stage after 2.5 s. After cooling for 154 s, at the end of Stage 2, the WRS distribution was fundamentally shaped except for in the cladding layer. The interface between the cladding layer and substrate is the most heavily damaged region due to the severe stress gradient and drastic change in WRS during the welding process. The effects of substrate thickness and preheat temperature were evaluated. The final WRS in the cladding layer first increased with the increase in substrate thickness, and then started to decline when substrate thickness reached a large-enough value. WRS magnitudes in the substrate and SAL decreased with the increase in preheat temperature and substrate thickness. Compressive WRS in the cladding layer, on the other hand, increased with the increase in preheat temperature.

Evaluation of hydrogen trapping and diffusion in two cold worked CrMo(V) steel grades by means of the electrochemical hydrogen permeation technique

Hydrogen diffusion kinetics, which is influenced by the hydrogen trapping and de-trapping phenomena within the steel microstructure, plays an important role on the behaviour of steel components under hydrogen environments. Hence, the complex interaction between hydrogen atoms and steel microstructure must be analyzed in order to discuss the impact of hydrogen on the structural damage.Quenched and tempered low-alloy ferritic steels from the Cr-Mo family, with and without vanadium, have been subjected to different plastic deformation ratios by cold rolling. Dislocation densities have been determined by the analysis of the peak broadening on X-Ray diffractograms. Hydrogen diffusion kinetics was characterized by means of hydrogen permeation transients. In addition, binding energies between hydrogen atoms and microstructure were also determined using thermal desorption analysis (TDA). The analysis of the results highlights the influence of dislocations density and vanadium carbides on the hydrogen diffusion kinetics. In the 2.25Cr1Mo steel grade, hydrogen apparent diffusion coefficient decreased after the cold-work due to the increase in the density of traps (mainly related to dislocation core, ΔETL = 55–60 kJ/mol). Nevertheless, after 10% of plastic deformation, apparent diffusion coefficient ‘saturates’ according to the ‘plateau’ determined in the dislocation density evolution at higher deformation levels. Due to the vanadium addition (+0.31%), hydrogen apparent diffusion coefficient was notably reduced (compared to that obtained in the V-free steel grade). Hydrogen trapping and diffusion are the result of the interplay between vanadium carbides (ΔETL = 35 kJ/mol) and dislocation core.

In situ friction and wear behavior of rubber materials incorporating various fillers and/or a plasticizer in high-pressure hydrogen

Polymers are used routinely for equipment and infrastructure in hydrogen vehicle refueling stations, but significant gaps remain in understanding their hydrogen compatibility. The tribological properties of these materials in a high-pressure hydrogen environment is important in preventing component failure and the need for frequent replacement. We present in situ tribological studies on model rubbers, which include common fillers and plasticizer, using an in situ tribometer developed previously. Results suggest a clear, yet complicated, combined effect of the high-pressure hydrogen and the additives on the tribological performance of the chosen materials, as compared to matching experiments performed in ambient air. We find that the additives improved wear resistance in EPDM but deteriorated that in NBR due to disparate additive-polymer interactions.

Hydrogen environment assisted cracking in X70 welding heat-affected zone under a high-pressure hydrogen gas

In this study, the susceptibility of API X70 weld joints to hydrogen gas was investigated using slow strain rate tensile (SSRT) tests. The microstructure of the subregion of the actual heat-affected zone (HAZ) weld joint was reproduced by weld thermal-cycle simulation techniques. The SSRT results showed that the weld and cross-weld specimens had the highest hydrogen embrittlement (HE) susceptibility, followed by the subregions of the fine-grained heat-affected zone (FGHAZ) and coarse-grained heat-affected zone (CGHAZ) specimens and the base metal. The HE index ranking of the samples was as follows (in increasing sequence): weld, cross-weld, simulated FGHAZ, simulated CGHAZ, and base metal specimens. The rupture location of the cross-weld specimen in ambient air is different to that tested in 10 MPa H2. The higher susceptibility of the weld and cross-weld specimens was primarily attributed to synergic effects between the microstructural characteristics, stress localization, and microhardness distribution – particularly, microhardness plays an important role in the nucleation of microcracks and the hydrogen diffusion rate induced by stress/strain localization.

Preparation and characterization of zinc gallate phosphor for electrochemical luminescence

Zinc gallate (ZnGa2O4) phosphor was fabricated by the direct precipitation method (DPM) and solid state reaction method (SSRM). The physicochemical and electrochemical properties of ZnGa2O4 phosphor were investigated using X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV). Finally, the prepared ZnGa2O4 electrode was examined for electrochemical luminescence (ECL). The ZnGa2O4 phosphors showed nano-sized particles at about 10 nm for DPM and 75 nm for SSRM. This electrode showed good conductivity in the reducing hydrogen environment and enhanced luminescence efficiency. The ECL emission intensity of the ZnGa2O4 electrode of DPM was 30 times higher than that of SSRM. This electrode exhibited strong green emission peak intensity of ECL at a wavelength of 520 nm from the excitation of 254 nm wavelength. The nano-sized ZnGa2O4 electrode of DPM led to effective quenching in an ECL study. Therefore, it had a good luminescence stability.

The Effect of in Situ Phenol Hydrogenation with Raney Ni on the Fate of Hydrogen from Glycerol Aqueous Phase Reforming

The fate of hydrogen during glycerol aqueous phase reforming (APR) and the effect of in situ phenol hydrogenation (IGAPH) with Raney Ni on the glycerol APR mechanism were studied. Glycerol APR proceeds through parallel routes via 1,2-propylene glycol or ethylene glycol. Combining phenol hydrogenation with glycerol APR changes the distribution of hydrogen among products. Hydrogen for hydrogenolysis of glycerol APR intermediate products was diverted to phenol hydrogenation, leading to enhanced glycerol conversion and suppressed hydrogenolysis. This hydrogen transfer occurred on the catalyst surface without formation of hydrogen gas as indicated by empirical results from open/closed system reactors. The lean hydrogen environment induced by hydrogen scavenging phenol on Raney Ni promoted the ethylene glycol route generating additional hydrogen for phenol hydrogenation. Moreover, removal of CO2 by adjusting process pressure in the open system can enhance phenol conversion during IGAPH and eliminate the burden of operating at autogenous high pressure. In addition to producing renewable hydrogen from glycerol and water, in situ APR-hydrogenation eliminates the transport barrier of gaseous hydrogen diffusion into solution.

Hydrogen embrittlement susceptibility of X70 pipeline steel weld under a low partial hydrogen environment

The present study investigates the effects of a low partial pressure of hydrogen in a mixture with methane gas on the mechanical properties of welded API X70 pipeline steel using a series of smooth tensile and notched tensile, testing approaches. The microstructures and mechanical property performances of the weld metal are compared to the results obtained for the base metal. The weld metal was found to be more vulnerable to hydrogen-induced crack initiation than the base metal. A significant loss of ductility occurred in the weld metal, even when tested under 10 MPa of a gas mixture with 1% H2 using the smooth tensile specimen. The notched reduction in the area (RA) decreased markedly under 10 MPa gas mixtures with 1% H2. The microstructural inhomogeneity in the metal matrix was associated with a more severe hydrogen-assisted fracture in the weld metal. The hydrogen-induced crack initiation primarily occurred at the interface between the dendritic pro-eutectoid ferrite and bainitic ferrite and propagated with the dendritic ferrite in which the diffusion of hydrogen was promoted by the stress/strain incompatibility and localized deformations.

Oxygen vacancies and F+ centre tailored room temperature ferromagnetic properties of CeO2 nanoparticles with Pr doping concentrations and annealing in hydrogen environment

We have investigated ferromagnetic and optical properties, local geometrical structure for Ce1-xPrxO2 (x = 0, 2, 4, 6 and 8% Pr doping) co-precipitation method-synthesized nanomaterials, which were hydrogenated subsequently. Dopant ion concentration, its valence state and effect of hydrogen annealing are correlated with oxygen vacancies and their role in magnetism is discussed with X-Ray diffraction, Raman spectroscopy and Magnetic measurements. The results support the fluorite structure formation for Pr-doped CeO2 nanomaterials without any impurity phase. Red shifting of band gap energy with increased Pr concentration can be seen in the absorption spectra. Raman active modes at ∼500-650 cm−1 confirm the formation of oxygen vacancies, varying with Pr4+/Pr3+ ions in the CeO2 lattice. A sharp peak at ∼3611 cm−1 in FTIR spectra broadens on interaction with H, due to combination of Hydrogen with adjacent Oxygen forming OH moiety within the CeO2 lattice. The magnetization results performed at room temperature confirm ferromagnetic signal for all the samples, with enhanced/reduced FM ordering for different Pr doping fluencies, explained by F-Centre exchange Mechanism with the formation of various complexes, Ce4+-Vo-Ce3+, Pr4+-Vo-Ce3+, or Pr3+ -Vo-Ce3+ in the CeO2 lattice. These nanomaterials are suitable for various applications e.g. Solid state electrolyte for fuel cells, UV blockers, photo-catalyst, magneto-optic devices and primarily for spintronics applications.

Hydrogen-assisted fatigue crack-propagation in a Ni-based superalloy 718, revealed via crack-path crystallography and deformation microstructures

Fatigue crack-growth (FCG) of Ni-based superalloy 718 was investigated under gaseous hydrogen environment (external hydrogen) and uniformly pre-charged state (internal hydrogen). Under external hydrogen, intergranular fracture predominated, whereas dislocation slip-band or twin boundary fracture were prevalent under internal hydrogen. This failure mode divergence encompassed unique characteristics of macroscale FCG response, leading to both cycle- and time-dependent cracking. The intergranular cracking was ascribed to short-circuit diffusion of hydrogen along grain boundaries. Meanwhile, the material’s inherently inhomogeneous deformation mode exerts harmfulness when hydrogen was uniformly distributed inside the specimen, causing slip-bands or twin boundaries to become the weakest links for fracture.

Microstructural evolution of Mo-UO2 cermets under high temperature hydrogen environments

Ceramic-metallic (cermet) materials show promise for use in nuclear thermal propulsion applications due to attractive thermophysical properties including high temperature stability and high thermal conductivity. In this work, molybdenum-uranium dioxide (Mo-UO2) cermet fuel elements were fabricated by means of spark plasma sintering (SPS) and were subsequently exposed to hydrogen at high temperatures (2500 K). Mo-UO2 samples pre- and post-exposure were characterized by means of optical microscopy, scanning electron microscopy, and X-ray diffraction (XRD). Microscopy analyses of the as-produced material displayed microscopic cracking on the interior of the spherical UO2 fuel particles but confirmed that the fuel particles were fully encapsulated in the Mo matrix. The results further showed mass loss, macroscopic swelling, and cracking in the cermet samples which occurred during high temperature hydrogen testing. Nanoscale swelling was evidenced by XRD in the Mo matrix and UO2 fuel structure due to the incorporation of defects and accompanied microstrain.

Carbon ionization at gigabar pressures: An ab initio perspective on astrophysical high-density plasmas

A realistic description of partially-ionized matter in extreme thermodynamic states is critical to model the interior and evolution of the multiplicity of high-density astrophysical objects. Current predictions of its essential property, the ionization degree, rely widely on analytical approximations that have been challenged recently by a series of experiments. Here, we propose a novel ab initio approach to calculate the ionization degree directly from the dynamic electrical conductivity using the Thomas-Reiche-Kuhn sum rule. This Density Functional Theory framework captures genuinely the condensed matter nature and quantum effects typical for strongly-correlated plasmas. We demonstrate this new capability for carbon and hydrocarbon, which most notably serve as ablator materials in inertial confinement fusion experiments aiming at recreating stellar conditions. We find a significantly higher carbon ionization degree than predicted by commonly used models, yet validating the qualitative behavior of the average atom model Purgatorio. Additionally, we find the carbon ionization state to remain unchanged in the environment of fully-ionized hydrogen. Our results will not only serve as benchmark for traditional models, but more importantly provide an experimentally accessible quantity in the form of the electrical conductivity.

The synergistic effects of hydrogen embrittlement and transient gas flow conditions on integrity assessment of a precracked steel pipeline

We are reporting in this study the hydrogen permeation in the lattice structure of a steel pipeline designed for natural gas transportation by investigating the influence of blending gaseous hydrogen into natural gas flow and resulted internal pressure values on the structural integrity of cracked pipes. The presence of cracks may provoke pipeline failure and hydrogen leakage. The auto-ignition of hydrogen leaks, although been small, leads to a flame difficult to be seen. The latter makes such a phenomenon extremely dangerous as explosions became very likely to happen. In this paper, a reliable method is presented that can be used to predict the acceptable defect in order to reduce risks caused by pipe failure due to hydrogen embrittlement. The presented model takes into account the synergistic effects of transient gas flow conditions in pipelines and hydrogen embrittlement of steel material due to pressurized hydrogen gas permeation. It is found that blending hydrogen gas into natural gas pipelines increases the internal load on the pipeline walls due to overpressure values that may be reached in a transient gas flow regime. Also, the interaction between transient hydrogen gas flow and embrittlement of API 5L X52 steel pipeline was investigated using Failure Assessment Diagram (FAD) and the results have shown that transient flow enhances pipeline failure due to hydrogen permeation. It was shown that hydrogen embrittlement of steel pipelines in contact with the hydrogen environment, together with the transient gas flow and significantly increased transient pressure values, also increases the probability of failure of a cracked pipeline. Such a situation threatens the integrity of high stress pipelines, especially under the real working conditions of hydrogen gas transportation.