INFLUENCE OF GAS MIXTURES OF HYDROGEN WITH METHANE ON THE OPERATIONAL AND THERMOPHYSICAL CHARACTERISTICS OF POLYETHYLENE PIPES OF OPERATING GAS DISTRIBUTION NETWORKS OF UKRAINE

The paper presents the results of complex studies of the influence of mixtures of hydrogen gas with natural gas in the ratios of 10%Н2/90%СН4 and 20%Н2/80%СН4 on the operational and thermophysical characteristics of PE-80 polyethylene pipes and their material Research was conducted on an experimental stand, the diagram of which is attached. The results of comprehensive strength and thermophysical studies of the material of PE-80 polyethylene pipes, which were previously operated in the current gas distribution networks of Ukraine for 15 years, after 6 months of hydrogen exposure, are presented. In order to indicate possible changes in the properties of the material, the same complex of studies was carried out before hydrogen exposure of the samples. The influence of gas mixtures on the thermophysical properties of polyethylene pipes has been established, which is manifested in the reduction of the size of polyethylene crystallites and their orderliness in the volume of pipe walls under the influence of gas mixtures. At the same time, the appearance of crystallites of a new shape was found on the surface of the inner wall of the pipes. It is assumed that this may be caused by the competing action of methane and hydrogen molecules. In the course of conducting hydraulic tests on the resistance of pipes to internal pressure and mechanical studies on uniaxial tension, it was determined that all pipe samples, according to their strength characteristics, meet the requirements of regulatory documents issued for polyethylene pipes used for natural gas transportation. The relationship between the concentration of hydrogen in the mixture and the degree of its influence on the strength characteristics of the samples was established. No changes in the chemical structure of the material of polyethylene pipes were detected. It should be noted that the given results are only the beginning of a more detailed study, during which it is also planned to investigate the effect of hydrogen mixtures on technical polyethylenes after 12 and 24 months of hydrogen exposure. Bibl. 17, Fig. 11, Tab. 2.