【Ten Years of Great Progress in Chemical Engineering Technology】Weldless internal anti-corrosion technology for small-diameter pipes from 2014 to 2021

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This post was last edited by Desert Fish on 2023-7-14 at 11:18. Significant progress has been made in chemical technology over the past decade; may China continue to thrive and prosper. This is just a starting point – more participation from everyone will make things even more lively. The forum becomes better with your involvement; we welcome everyone to join in the discussions. It’s hot in July, so be careful to prevent fires. ---------------------------------------------- Recently, news came from China National Petroleum Pipeline Bureau’s Anti-Corrosion Company: the results of the research on \"Mechanical connection techniques and processes for maintaining the continuity of pipeline coatings\" carried out by this company have successfully passed field testing. This marks a new construction approach for the building of long-distance pipelines with diameters of 100 millimeters or less; the pipeline construction company has introduced a weld-free era for the construction of pipelines with small diameters. 　　It is understood that the techniques for repairing anti-corrosion coatings inside domestic pipelines mainly include the method of welding first and then repairing, the method of repairing first and then welding, and the method of not repairing after welding. Currently, the more commonly used technique is the one that involves welding first and then repairing, specifically the mechanical cart spraying method for internal repairs. However, this internal sealing technique has certain limitations and is not suitable for small-diameter pipes. Especially in pipes with a diameter of 100 millimeters or less, there are common risks such as pipe corrosion and leakage caused by the absence of an anti-corrosion layer at the weld areas. 　　Technicians from anti-corrosion companies explain that pipeline corrosion poses a threat to the safety and long-term operation of pipelines; compared to reliable external anti-corrosion techniques, internal anti-corrosion methods are clearly a weak point. According to investigations, 90% of pipeline corrosion occurs on the inner walls of the pipelines, with corrosion failure at the inside of welds accounting for the vast majority of such cases. There is no effective solution to this technical problem at the international level either. 　　After becoming aware of this situation through its participation in the construction of the surface transportation pipelines at the Changqing Oil Field, the anti-corrosion company identified the need to address the anti-corrosion requirements for pipelines in the context of such pipeline constructions as well as future domestic projects involving small-diameter pipes. It then embarked on research regarding the selection of mechanical connectors, the anti-corrosion treatment of both the interior and exterior of these connectors, the sealing and anti-corrosion protection of steel pipe ends, construction equipment, construction methods, and related standards. Over the past two years, the research institute of the anti-corrosion company has, through various investigations, literature reviews, and thorough comparisons, proposed the idea of using mechanical connectors to join steel pipes and eliminating the need for space reserved for pre-formed welds for anti-corrosion purposes, in order to achieve a 100% coverage rate for the internal anti-corrosion layer. 　　To verify the feasibility of this project, the anti-corrosion company actively sought cooperation with Changqing Oilfield and took on the task of constructing 2 kilometers of pipeline systems at Oil Production Plant No. 8. The project is located in Tiebian Town, Wuqi County, Yan’an City, Shaanxi Province, with a pipe diameter of 76.1 millimeters. During construction, on-site personnel use mechanical joining techniques to \"weld\" the pipes, and employ an external anti-corrosion method that involves \"viscoelastic materials combined with heat-shrinkable sleeves\"; the joint ends are sealed using solvent-free liquid epoxy. After one year of operation, the anti-corrosion company assembled renowned experts from industries such as pipeline bureaus and pipeline companies to form an expert team to conduct on-site excavation verification. The results showed that there were no cracks, wrinkles, bulges, or leakage points in the coating, indicating that the entire anti-corrosion system was functioning properly. 　　“The interference crimping technology for internal coatings of pipelines developed by anti-corrosion companies features stable quality and reliable performance; it ensures the continuity and integrity of the internal coatings in transportation pipelines. It also provides a reliable technical solution for connecting thin-walled transportation pipelines, making it suitable for wide-scale application in oil fields. ”Huang Liuqun, an anti-corrosion expert from the Pipeline Bureau, said, “In addition, mechanical connection technology also has unique advantages in construction.” Taking the welding of a pipe joint with a diameter of less than 100 millimeters as an example, compared to traditional welding methods, the use of mechanical joining techniques not only helps to save costs but also increases work efficiency by more than 4 times. ” 　　“Restricted by factors such as equipment and technology, mechanical joining techniques cannot fully replace welding. However, due to their fire-free nature, they have inherent advantages in pipelines for oil and gas field surface operations, stations, and special locations, offering very promising market prospects. ”Liu Yuefang, director of the R&D institute at the anti-corrosion company, explained. 　　To date, the anti-corrosion company has filed 2 **patents**, prepared the Pipeline Bureau’s corporate standard titled \"Technical Requirements for the Use of Weldless Pipe Connection Devices\" along with the corresponding operating procedures, and possesses a complete set of construction equipment. The next step is to strive for widespread adoption of these technologies.