MAGNETIC-PULSED TREATMENT TO IMPROVE THE STRENGTH PROPERTIES OF DEFECTIVE SECTIONS OF OIL AND GAS PIPELINES

Link for citation: Schipachev A.M., Mohammed Aljadly. Magnetic-pulse treatment to improve the strength properties of defective sections of oil and gas pipelines. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 5, рр.7-16.In Rus. The relevance. During the operation of oil and gas pipelines, continuity defects (including point and linear defects such as delamination, cracks of various nature, etc.) occur in their structure. The peculiarity of material continuity defects is caused by the fact that in the process of loading the defects cause stress concentration near their tops, which leads to a rapid increase in their number and geometric dimensions, followed by the merging of the latter and the formation of large discontinuities, and as a consequence, the strength properties of pipelines decrease. Consequently, early detection of metal continuity defects and their elimination before they reach a critical size are urgent tasks. The solution of which will significantly improve the operational and strength properties of the working elements of pipelines and extend their lifespan. The main aim of the research is to study the effectiveness of magnetic-pulse treatment to improve the strength properties of used oil and gas pipelines by reducing the defects size. Objects: defective sections of main oil and gas pipelines. Methods: magnetic pulse treatment of samples on a magnetic-pulse unit MPU-10-SSAU 10, determination of temperature changes caused by magnetic-pulse treatment, testing samples for impact strength on a pendulum-testing machine, comparison of the obtained results for treated and untreated samples, determination of the effect of magnetic-pulse treatment on the strength properties of gas pipeline metal, study of the fracture surface of samples after impact tests. Results. It was established experimentally that the impact strength of the treated samples increased by 14 % compared to the untreated samples. Snapshots of the temperature distribution during the magnetic-pulse treatment showed a significant increase in temperature near the crack tips. It was found that destruction of the metal subjected to magnetic-pulse action acquired more viscous character

Magnetic-pulsed treatment to improve the strength properties of defective sections of oil and gas pipelines

Актуальность. В процессе эксплуатации нефте- и газопроводов в структуре металла их стенок возникают дефекты сплошности (поры, расслоения, трещины различной природы и др.). Особенность данных дефектов обусловлена тем, что при эксплуатационных нагрузках в их вершинах возникает концентрация напряжений, что приводит к росту количества дефектов и геометрических размеров с последующим слиянием последних и образованием крупных дефектов и, как следствие, снижению прочностных свойств металла трубопроводов. Раннее выявление дефектов сплошности металла и их устранение до того, как они достигнут критического размера, являются актуальными задачами, решение которых повысит надежность и прочностные свойства металла трубопроводов, а также продлит их ресурс. Цель: исследование эффективности магнитно-импульсной обработки для повышения прочностных характеристик металла стенки бывших в эксплуатации нефте- и газопроводов путем уменьшения размеров дефектов. Объекты: дефектные участки магистральных нефте- и газопроводов. Методы: магнитно-импульсная обработка образцов из стали 17Г1С бывшего в эксплуатации магистрального газопровода диаметром 720 мм, содержащих коррозионное растрескивание под напряжением, на магнитно-импульсной установке МИУ-10- СГАУ, определение изменений температуры, вызванных магнитно-импульсной обработкой, испытание образцов на ударную вязкость, определение влияния магнитно-импульсной обработки на прочностные свойства металла газопровода, исследование поверхности излома образцов после испытаний на ударную вязкость. Результаты. Экспериментально было установлено повышение на 14 % ударной вязкости обработанных магнитно-импульсной обработкой образцов по сравнению с необработанными образцами. Снимки распределения температуры при магнитно-импульсной обработке показали значительное повышение температуры вблизи вершин трещин. Было выявлено, что разрушение металла образцов, подвергнутых магнитно-импульсному воздействию, приобрело более вязкий характер.The relevance. During the operation of oil and gas pipelines, continuity defects (including point and linear defects such as delamination, cracks of various nature, etc.) occur in their structure. The peculiarity of material continuity defects is caused by the fact that in the process of loading the defects cause stress concentration near their tops, which leads to a rapid increase in their number and geometric dimensions, followed by the merging of the latter and the formation of large discontinuities, and as a consequence, the strength properties of pipelines decrease. Consequently, early detection of metal continuity defects and their elimination before they reach a critical size are urgent tasks. The solution of which will significantly improve the operational and strength properties of the working elements of pipelines and extend their lifespan. The main aim of the research is to study the effectiveness of magnetic-pulse treatment to improve the strength properties of used oil and gas pipelines by reducing the defects size. Objects: defective sections of main oil and gas pipelines. Methods: magnetic pulse treatment of samples on a magnetic-pulse unit MPU-10-SSAU 10, determination of temperature changes caused by magnetic-pulse treatment, testing samples for impact strength on a pendulum-testing machine, comparison of the obtained results for treated and untreated samples, determination of the effect of magnetic-pulse treatment on the strength properties of gas pipeline metal, study of the fracture surface of samples after impact tests. Results. It was established experimentally that the impact strength of the treated samples increased by 14 % compared to the untreated samples. Snapshots of the temperature distribution during the magnetic-pulse treatment showed a significant increase in temperature near the crack tips. It was found that destruction of the metal subjected to magnetic-pulse action acquired more viscous character

Evaluating the Effectiveness of Magnetic-Pulse Treatment for Healing Continuity Defects in the Metal of Oil and Gas Pipelines

This research paper addresses the issues in evaluating the effectiveness of magnetic-pulse treatment for healing continuity defects in the metal of oil and gas pipelines. A theoretical analysis of the magnetic-pulse action mechanism on continuity defects in the metal was carried out. The results of experimental studies of the effect of magnetic-pulse action on continuity defects of thick-walled samples, cut from used gas pipelines containing microcracks with different geometries, are also presented. The samples were processed under two different technological operating modes of the magnetic-pulse unit: the applied energy was 10 kJ for the first mode and 20 kJ for the second mode. The state of the cracks’ microstructure before and after the magnetic pulse treatment was studied using an optical microscope. As a result of the studies, it was found that magnetic-pulse treatment led to local heating of the crack tips, which was confirmed by the formation of a heat-affected zone in the vicinity of the crack tips. The temperature at the crack tips reached the metal’s melting point at the applied energy of 20 kJ, whereas at the energy of 10 kJ, signs of metal melting were not noted. In the course of the conducted experiments, it was found that the cracks were not completely eliminated after magnetic-pulse treatment; however, the edges of the crack tips melted, with subsequent filling by molten material. Magnetic-pulse treatment resulted in blunting of the crack tips, as their shape became smoother. It was established that the geometry and shape of the crack tip have significant influences on the effectiveness of this technology, as a narrow and sharp crack tip required less energy to reach the metal’s melting point compared to smoother one. The effect of magnetic pulse treatment on the microstructure of pipeline metal and its strength characteristics was also studied. It was found that this treatment leads to structural changes in the area of the crack tip in the form of grain refinement and subsequent strengthening of the pipeline metal