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.

One of the main reasons for oil-field pipeline failure is groove corrosion. The residual life of such pipelines is estimated based on defectoscopy corrosion rate—a ratio of the formed «groove» depth to the pipeline operation start time. In this case, it is supposed that, in the future, the «groove» will deepen at the same rate for the remaining period of the pipe’s operation. However, sometimes, oil-field pipeline operation experience shows that the remaining time of safe operation is much less than the calculated one. In this article, such a discrepancy is explained via the acceleration of the groove corrosion rate in the process of «groove» deepening due to the increasing level of mechanical stresses in the surrounding metal, which intensifies the corrosion process as a result of the mechanochemical effect. Based on a literature analysis and calculated data, the kinetic equation of the groove corrosion rate for an oil-field pipeline is proposed, which accounts for the acceleration of the process rate as the pipeline is operated and allows the more accurate estimation of its remaining service life.

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.

When transporting and storing hydrocarbons, one of the main operational problems is the external and internal corrosive wear of the metal. A frequent cause of accidents in main and technological gas pipelines due to their stress corrosion cracking is the enrichment of the pipe body with hydrogen. Literature experimental data on the effect of hydrogen on the hardness of iron and low-carbon steels during their electrolytic saturation with hydrogen are analyzed. It is noted that the curves of changes in hardness in all the analyzed sources for all these materials have a similar form: at the initial stage of hydrogenation, the hardness increases, reaching its maximum, and then it declines to values close to the initial level follows. At the same time, the time to reach the maximum hardness decreases with the introduction of promoters into the electrolyte solution, which can be Na2S, As. Increasing the current density during electrolysis increases the value of the maximum hardness. The time to reduce the hardness to the initial level is approximately the same as the hydrogenation time required to achieve maximum hardness. Possible explanations of the regularities obtained by the authors are given.

The work describes the experimental definition of the main factors that contribute to the emergence of grooving corrosion: availability of abrasive particles in flow which are transported in specific terms when they are capable of scratching the bottom generating line of a pipeline by creating stress concentrators; availability of considerable residual stresses in pipe metal; oxygen availability in reaction zone.

One of the key challenges hindering the safe transportation of compressed hydrogen and its mixtures with natural gas through existing pipeline systems is the potential hydrogen embrittlement (HE) of steel pipe materials. At the same time, there is no universally accepted method for screening pipeline steels for hydrogen resistance. The existing testing methodologies used to assess the suitability of steels for operation in contact with compressed hydrogen have been analyzed. The results of comparative experiments conducted by the authors using various methods demonstrate that the outcomes of screening pipeline steels for hydrogen compatibility, obtained through testing in aqueous hydrogen sulfide solutions versus compressed hydrogen environments, do not correlate with each other. For example, when testing two pipeline steels with strength classes K52 and X70 for stress corrosion cracking in an aqueous hydrogen sulfide solution, both steels showed negative results and were classified as non-resistant. However, when tested in a gaseous hydrogen environment, they were categorized according to conditional resistance levels to hydrogen degradation as "resistant" and "satisfactorily resistant," respectively. The satisfactory resistance of the analyzed steels to hydrogen embrittlement was further confirmed by the authors' experiments evaluating these materials' resistance to crack propagation in a compressed hydrogen environment, which allowed both steels to be classified as "suitable" for operation in hydrogen-containing conditions. It is concluded that the acceptability of a given steel for pipelines transporting compressed hydrogen and its mixtures with natural gas should be determined based on testing results in the actual operational environment of the gas pipeline.