【History of Haichuan Pipelines】The technology for laying multiple large-diameter pipes in the same trench was used for the first time in a field application involving the simultaneous laying of three large-diameter pipes in one trench

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On April 2, the pipeline project for Station 2 in Zhongwei, undertaken by the Pipeline Bureau, saw the first on-site application of laying three ultra-large-diameter pipes in the same trench, filling a gap in the industry and opening up new methods and approaches for protecting the ecological environment, saving land use, and reducing costs in China’s oil and gas pipeline sector. 　　The construction project featuring the installation of three large-diameter pipes in the same trench is located in Zhongwei City, Ningxia Hui Autonomous Region. It is the Zhongwei Station 2 construction project, which serves as the starting point for the middle section of the West-East Gas Pipeline Project III. Upon completion, Zhongwei Station 2 will become the largest natural gas transmission hub in the Asia-Pacific region. The project includes 1 station and 3 pigging stations, with 4 new pipelines constructed and 6 pipelines rerouted; the total length of the pipeline network is 24.91 kilometers. 　　The pipelines laid in three trenches pass through Shapotou District of Zhongwei City, adjacent to the Tengger Desert. The area has a fragile ecosystem, high requirements for ecological protection, and faces significant pressure in terms of soil and water conservation. 　　Wang Xuejun, general manager of the pipeline design institute, explained that the scale of constructing 10 pipelines converging at a single hub station is rare even in the global pipeline construction industry. The most advanced digital pipeline 3D design technology available in China was used this time to optimize the design plan for the Eweishan Station project on multiple occasions. Given that three pipelines share the same route, the design scheme of installing them in the same trench was ultimately adopted, which reduces the area disturbed by trench excavation by over 30%. 　　The section where the three pipelines are laid in the same trench is entirely located in mountainous areas, with a total length of 1.83 kilometers. It must pass through Gaoxianzi Gou and the Gaoxianzi Gou fault zone, making it a key control point for the construction of the Zhongwei Station 2 project. Company No. 2 for pipelines utilizes the next-generation cpp900 fully automatic welding system, which features one-key automatic alignment, precise positioning technology, and fully digital communication systems; as a result, the first-pass welding success rate exceeds 98%, ensuring stable and controlled quality. 　　“We have also innovatively adopted the weld seam spatial positioning method and the pipe pier laser positioning method to address the issue of welding stress in the weld seams, ensuring the accuracy of the spacing between the three pipes in the same trench and facilitating the smooth progress of pipeline construction. ”Xiang Binrui was told by the project manager of Zhongwei No. 2 Station at Pipeline Company No. 2. 　　The three-pipe in-trench system used this time consists of two pipes with a diameter of 1422 millimeters and one pipe with a diameter of 1219 millimeters, all laid parallel in a 15-meter-wide trench, with the minimum distance between pipes being as low as 1.5 meters. 　　Wang Xuejun said that by employing the technology of laying multiple large-diameter pipes in the same trench, this project saves 37.5% of the land required for construction and reduces project costs by around 12%. The successful application of this technology can lay a solid foundation for the planning and construction of large-scale pipeline corridors for energy transmission. 　　The middle section of the West-to-East Gas Pipeline Project Phase III began construction in September 2021. With a total length of 2,090 kilometers, it starts from Zhongwei in Ningxia and passes through seven provinces and regions including Ningxia, Gansu, Shaanxi, Henan, Hubei, Hunan, and Jiangxi, ending in Ji’an in Jiangxi. As a backup station for the currently in use Zhongwei compression station, upon completion, Zhongwei Station 2 will enable connectivity between Line West 1, Line West 2, Line Zhonggui, Line Zhongjing, as well as the western section of Line West 3 and the middle section of Line West 3. This will help alleviate the load on the existing Zhongwei compression station and distribute risks, which is of great significance for improving the interconnectivity of energy pipelines.