Liquefied natural gas (LNG) is one of the most promising fuels for energy supply because it has a favorable combination of environmental and economic properties in connection with new trends aimed at the development of ecological and sustainable consumption of natural resources, which ensure a constant growth in LNG consumption. The article presents an analytical review of the main technical solutions for the construction of cryogenic pipelines and insulating coating structures. The ANSYS Fluent software was used for simulation of the LNG flow in a pipeline section 10 m long with an outer diameter of 108 mm for three types of insulating coating (polyurethane (PU) foam, aerogel, and vacuum-insulated pipe (VIP)). In addition, an assessment was made of the insulating effect on the LNG temperature distribution along the length of the pipeline. The largest increase in temperature from 113 K to 113.61 K occurs in PU foam-insulated pipes; the smallest was observed in VIP. Further, as an alternative to steel, the use of ultra-high molecular weight polyethylene (UHMWPE) for pipeline material was considered. The optimal result in terms of temperature distributions was obtained while simulating the flow of an LNG pipeline with PU foam by increasing the thickness of the insulating coating to 0.05 m.

The transportation of oil and gas in Russia’s northern and Arctic regions has seen significant growth in recent years. However, the presence of permafrost in these areas can cause malfunctions in the main pipelines due to soil frost heaving. The operational pipelines also often suffer from various defects in their body and surface. To mitigate these issues, above-ground trunkline supports are utilized to protect the pipelines from cryogenic processes. Nevertheless, these supports are subjected to ground loads caused by cryogenic frost heaving, which poses a threat to the pipeline’s integrity and the environment. In response to these challenges, this study presents a design for pipeline support to maintain the pipeline’s stability in the face of soil displacement caused by unequal frost-heaving forces. A numerical model was created to evaluate the fracture of frozen rock and the resulting stresses in the soil and support structure. The input data for the model includes coefficients that describe the soil’s state during the cryogenic process and the proposed support’s parameters. The experimental results showed the proposed design to be effective in protecting the pipeline from soil frost heaving. The paper also provides the results of numerical and experimental studies on soil fracture stresses depending on the rock type and temperature. This design promises to increase both the safety of above-ground trunk pipelines and their technological efficiency.

During the operation of main pipelines, many defects occur in the body of the pipe and on its surface. The main method for eliminating such defects is cutting out the defective section and welding a new one in its place. The cutting process is complicated by the possible sharp displacement of the ends of the pipeline located on both sides of the cutting site, which is dangerous for the lives of workers and can lead to breakage of the cutting equipment. In addition, to weld a new section, it is necessary to center the ends of the pipeline until they reach the alignment position, for which heavy, difficult-to-transport pipelayers are used, which allow centering the ends of the pipeline only by lifting them. Ensuring the possibility of such centering often requires additional digging of the repaired pipeline. Moreover, due to the large dimensions of pipelayers, payment of permits for their transportation is required. In addition, before transportation, pipelayers require their disassembly and assembly before carrying out repair work, which entails additional time and labor costs. To solve the problems described in this article, a developed design of devices for fixing and centering the ends of the pipeline is proposed, which makes it possible to fix the ends of the pipeline from their sharp displacement, and also to center them before welding a new section. A mathematical model was developed to assess the centering forces, the resulting stresses in the pipeline wall and the reaction forces that arise in the hydraulic cylinders of devices when leaving the ends of the pipeline in their sharp displacement. The initial data for the developed model are the coefficients of the polynomial describing the position of the pipeline in the repair trench. To accurately assess the position of the pipeline, a method of its laser scanning is proposed, the result of which is a point cloud of the pipeline. As part of the study, a method was also developed for the obtaining of a polynomial equation describing the bending of its central axis from a pipeline point cloud. As a result of experimental studies, this method has demonstrated sufficient accuracy in determining the position of the pipeline in the repair trench. Thus, the developed repair method makes it possible to increase both the safety of the repair and the technological and economic efficiency of the process of replacing a defective section.

Актуальность исследования обусловлена необходимостью повышения эксплуатационной надежности надземных магистральных трубопроводов, проложенных на многолетнемерзлых грунтах. Это направление развития транспортировки нефти и газа и наращивания сырьевого потенциала является ресурсосберегающим, минимизирующим объемы эксплуатационных затрат на обследование и геомониторинг. Опоры надземных магистральных трубопроводов подвергаются нагрузкам со стороны грунта из-за опасных криогенных процессов морозного пучения, вызванных очень низкими температурами. Появляется задача повышения эксплуатационной надежности надземных магистральных трубопроводов, проложенных на многолетнемерзлых грунтах. Цель: определить и предложить конструкцию опоры для надземных магистральных трубопроводов, проложенных на многолетнемерзлых грунтах, и возможность эффективного использования острой кромки опорной плиты в качестве основания надземной опоры. Объекты: надземный магистральный трубопровод, конструкция опоры, многолетнемерзлый грунт. Грунты классифицируются по типам и характеризуются сильным пучением и высоким модулем деформации. Методы: математическое моделирование опорной плиты с мерзлым грунтом; оценка и анализ распределения напряжения разрушения мерзлой породы; оценка эффективности применения новой конструкции опоры с острой кромкой опорной плиты в районах сплошного распространения многолетнемерзлых пород. Результаты. Даны физические характеристики мерзлых вспученных грунтов; предложена опорная конструкция, защищающая надземный магистральный трубопровод от воздействий сил морозного пучения; предложен оптимальный угол острой кромки опорной плиты для эффективного резания вспученного грунта; выполнено моделирование опорной плиты с мерзлым грунтом; выполнен расчет эквивалентных напряжений острой кромки при наиболее вероятном случае резания вспученной глины от воздействий сил морозного пучения грунта.

During the operation of above-ground main oil and gas pipelines, their elastic bends occur due to the properties of the soils in which the pipeline bases are installed, climatic factors, and the intersection of geodynamic zones. Exceeding the stress values in the pipeline wall above their permissible values leads to a rupture of the wall metal and major accidents. Most methods for estimating the values of bending stresses in the pipeline wall cannot be implemented during their operation, when the pipeline already has a bend, and the installation of any additional equipment on the pipeline requires additional investments. At the same time, the most widely used method for estimating bending stresses based on data from in-pipe diagnostics does not allow for evaluation in areas with varying internal diameters of the pipeline, as well as right-angle turns. The most promising method for estimating bending stresses is aerial laser scanning of pipelines, which consists of obtaining a cloud of points on the pipeline surface, estimating its spatial position, and calculating stress values. However, this method requires the development of more accurate algorithms for processing laser scanning data, and the method is associated with a number of difficulties that can be eliminated by developing the correct sequence of actions during scanning. Within the framework of this article, an algorithm has been developed for analyzing the coordinates of a cloud of points on the pipeline surface, which makes it possible to estimate the values of bending stresses in the pipeline wall. The influence of the unevenness of the thermal insulation surface on the stress assessment results was also studied, taking into account the minimum angle of the scanned pipeline sector, which ensures the accuracy of determining stress values up to 5% using the developed method.