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1

Increase of the technogenic and ecological safety of the natural gas transportation due to displacement of explosive mixtures with nitrogen

100%

Mandryk O. , Vytyaz O. , Poberezhny L. , Mykhailiuk Y.

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tom Vol. 106, nr 1

17--27

EN

Purpose: To ensure technological and environmental safety it is proposed to use the technology of purging pipeline with compressed nitrogen. Design/methodology/approach: The purpose of the calculation is: to get the graph of the concentration distribution (in volume fraction) of nitrogen and natural gas components depending on the distance from the injection point of nitrogen and the duration of the purge process, to determine of parameters of a non-stationary process, and to establish the optimal parameters of the purging process under conditions of the given flow chart. Findings: In the process of displacement of natural gas, the velocity of the front of nitrogen is one of the main quantities that significantly affect the quality of displacement. To assess the actual technological schemes for transporting natural gas, it is necessary to select the velocity of displacement of explosive mixtures. Research limitations/implications: This technology should be implemented in the conditions of a nitrogen pressure higher than 0.25 MPa. Practical implications: Most favourable conditions for the complete displacement of air and subsequent replacement of nitrogen with natural gas were observed for pressures higher from 1.0 to 1.5 MPa. Originality/value: Complex calculations of the volume of air displaced with nitrogen and natural gas in the process of filling the pipeline were conducted in the research. Boundary conditions on the concentration of the mixture of nitrogen and natural gas were identified.

2

Numerical simulation of the stress state of an erosion-worn tee of the main gas pipeline

75%

Doroshenko Y. , Zapukhliak V. , Grudz Y. , Poberezhny L. , Hrytsanchuk A. , Popovych P. , Shevchuk O.

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tom Vol. 101, nr 2

63--78

EN

Purpose: To investigate the strength of tees with regard to their erosion wear, it is necessary to consider the complex three-dimensional geometric shape of the erosion worn inner surface of the tee. In addition, the study of the strength of the erosion worn tees of the main gas pipelines is complicated by the occurrence of additional stresses caused by changes in the direction of movement of the gas stream, resulting in an uneven pressure distribution in the inner cavity of the tee, and the temperature difference in its walls. Design/methodology/approach: Methodology for complex numerical three-dimensional simulation of the stressed state of tees of the main gas pipelines, taking into account the gas-dynamic processes that occur in the places of these defects, erosion wear of the tee wall, temperature difference in the tee walls. Findings: The acceptable parameters of erosion defects of tees of gas pipelines, and residual life of tees with erosion defects of the wall should be determined. Research limitations/implications: The developed model does not take into account internal corrosion and corrosion products as an additional erosion factor. Further studies plan to develop a model of corrosion-erosion wear of pipeline elements. Practical implications: The developed technique allows determining the location of erosion defects, estimating the strength and determining the residual life of tees with erosion wear of the wall in order to ensure their reliability, to rank such defects according to the degree of danger, to determine which of them are critical and need an immediate repair. Originality/value: Based on the gas-dynamic processes occurring in the internal cavity of the main gas pipelines’ tees, the complex three-dimensional geometric form of wall erosion defects, and temperature difference, the technique of three-dimensional simulation of stress state of the main gas pipelines’ tees is developed

3

Gas hydrates impact on corrosion of the well flow lines material

63%

Poberezhny L. , Hrytsanchyk A. , Mandryk O. , Poberezhna L. , Popovych P. , Shevchuk O. , Mishchuk B. , Rudyak Y.

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2021

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tom Vol. 110, nr 1

5--17

EN

Purpose: Determination of regularities of joint action of mechanical stresses, formation water and hydrate formation on corrosion of material of flow pipelines. Design/methodology/approach: According to the analysis of reservoir water of the investigated deposits, it was found that the main corrosive component is soluble chlorides. Proposed for corrosion and corrosion-mechanical tests of 6 model environments. An estimation of the influence of stress concentration, depending on the defects of the inner wall of the pipe, was carried out, and the nominal local stresses in the pipeline was carried. Findings: The basic regularities of influence of stress and hydration formation on corrosion and localization of corrosion processes and on the kinetics of deformation of samples are described. For samples made of steel 20 and 17GS, an increase in the velocity of general and local corrosion for samples sustained in the gas hydrate was observed compared to the control results obtained, the coefficient of influence of the gas hydrate on corrosion was calculated. Research limitations/implications: The obtained results are valid for thermobaric operating conditions of well flow lines. Practical implications: The data obtained in the work on the patterns of corrosion processes and the impact of hydrate formation on them will allow to identify potentially dangerous areas of flow lines and prevent emergencies. Originality/value: Based on the analysis of the geometric dimensions of the defects, the effective stress concentration coefficients are calculated, and it is shown that the stresses in the vicinity of corrosion defects in normal operating modes range from 164 to 545 MPa.