Consideration of the possibility of transporting compressed hydrogen through existing gas pipelines leads to the need to study the regularities of the effect of hydrogen on the mechanical properties of steels in relation to the conditions of their operation in pipelines (operating pressure range, stress state of the pipe metal, etc.). This article provides an overview of the types of influence of hydrogen on the mechanical properties of steels, including those used for the manufacture of pipelines. The effect of elastic and plastic deformations on the intensity of hydrogen saturation of steels and changes in their strength and plastic deformations is analyzed. An assessment of the potential losses of transported hydrogen through the pipeline wall as a result of diffusion has been made. The main issues that need to be solved for the development of a scientifically grounded conclusion on the possibility of using existing gas pipelines for the transportation of compressed hydrogen are outlined.

The paper deals with a non-destructive method of detecting hydrogenated sections of pipelines, which is based on variations of the level of mechanical stresses generated in the surface layers of the steel pipe material during its hydrogenation. The use of a magnetoanisotropic method based on the phenomenon of metal magnetoelastic anisotropy development, which consists in the variation of the magnetic properties of ferromagnetic materials in direction and magnitude under the influence of mechanical stresses, is proposed as a way to register that variation. Based on the results of tensile testing of carbon steel plates with measurement of the difference in principal mechanical stresses (DPMS) occurring in metal, as well as experiments on electrolytic hydrogenation of specimens with measurement of the DPMS signal, it was confirmed that when steel structures are saturated with hydrogen, tensile stresses are generated in the surface layers, the magnitude of which increases as the concentration of hydrogen increases in the metal. In this case, it is assumed that the indicated dependence between the hydrogen concentration in the metal and the stresses arising as a result of hydrogenation is linear. For the example of lamellar specimens made of pipe low-carbon steel, the possibility of using the magnetoanisotropic method for registering sections of underground pipelines with a high content of hydrogen is substantiated, which can become the basis for a method of diagnosing sections of pipelines with broken insulation for the possibility of their further operation. The scientific novelty of this article is the establishment of a relationship between the hydrogen content in the metal, the stresses that arise in this case, and the change in the magnetic properties of ferromagnetic materials, characterized by the magnitude of the DPMS signal. This study contributes to the understanding of the process of hydrogenation of metals, and may be useful in detecting and preventing damage to gas and oil pipelines caused by hydrogen embrittlement as a cause of stress corrosion.

The production, transportation, and storage of liquefied natural gas (LNG) is a promising area in the gas industry due to a number of the fuel’s advantages, such as its high energy intensity indicators, its reduced storage volume compared to natural gas in the gas-air state, and it ecological efficiency. However, LNG storage systems feature a number of disadvantages, among which is the boil-off gas (BOG) recovery from an LNG tank by flaring it or discharging it to the atmosphere. Previous attempts to boil-off gas recovery using compressors, in turn, feature such disadvantages as large capital investments and operating costs, as well as low reliability rates. The authors of this article suggest a technical solution to this problem that consists in using a gas ejector for boil-off gas recovery. Natural gas from a high-pressure gas pipeline is proposed as a working fluid entraining the boil-off gas. The implementation of this method was carried out according to the developed algorithm. The proposed technical solution reduced capital costs (by approximately 170 times), metal consumption (by approximately 100 times), and power consumption (by approximately 55 kW), and improved the reliability of the system compared to a compressor unit. The sample calculation of a gas ejector for the boil-off gas recovery from an LNG tank with a capacity of 300 m³ shows that the ejector makes it possible to increase the boil-off gas pressure in the system by up to 1.13 MPa, which makes it possible to not use the first-stage compressor unit for the compression of excess vapours.

The results of electrolytic hydrogenation of 5 zones of vertically mounted 30x20x2 mm ARMCO-iron samples, differing in different locations on the central vertical of the sample (from bottom to top through 5 mm), in 5% H2SO4 solution with the addition of a 1.5 g/l CS(NH2)2 promoter at a cathode current density of 10; 17.5 and 25 mA/cm2 and the time of hydrogenation t is up to 35 minutes. It was found that, regardless of the measurement zone and current density, the change in the hardness of HV samples over time has the same form: an increase within 7.5 – 10 minutes from the initial (HV0 ~ 1,475 MPa) to the maximum value (HVmax up to 2,090 MPa), and then a decrease, with a significant difference between the values of ΔHVmaх = HVmax - HV0 for the lowest zone 1 (ΔHVmax = 615 MPa) and the highest 5 (ΔHVmax = 372 MPa). Zone 1 of the sample surface corresponds to the maximum number of “bubbles” (“blisters”), on some of which dark lines – cracks are recorded. The type of the established dependence ΔHV = f(t) is caused by the combined effect of two factors: distortion of the crystal lattice due to the introduction of hydrogen atoms into it and its compression by the pressure of molecular hydrogen located in micro-voids. Micro-voids are located in the surface layer of metal, When the pressure of hydrogen reaches a critical value in the “blisters”, they crack with the release of hydrogen into the atmosphere. This process is accompanied by a decrease in the compressive forces exerted by the blisters on the crystal lattice, with a decrease in its deformation and, as a consequence, the recorded hardness. The value of the maximum increment of hardness ΔHVmax in each zone of the sample depends on the number of “blisters” formed in this zone, and for this reason, decreases as the measurement zone rises upwards. A slight difference in the values of ΔHVmax of the samples after the completion of hydrogenation and after 30 days of exposure to air, sufficient for desorption of dissolved hydrogen from the metal, indicates that molecular hydrogen makes the main contribution to the distortion of the crystal lattice and the increase in the hardness of ARMCO-iron during hydrogenation. The studies were carried out with the involvement of the laboratory facilities of the Center for Collective Use of the Mining University.