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A Comprehensive Comparison of Seamless Steel and Welded Steel Pipe Galleries

Posted: 08/09/2021 13:46:43 Hits: 11

The application background of seamless steel pipes & welded steel pipes under comprehensive pipe gallery engineering conditions
Comprehensive pipeline galleries have developed rapidly in China this year. In 2013, the State Council proposed to reform the construction of a municipal underground pipeline to achieve the goal of 94% use rates for urban gas and 65% county town and small town in China. Launch a pilot project of an urban underground comprehensive pipe gallery. Fully launch the pilot project of underground comprehensive pipe gallery in 36 large and medium-sized cities across the country in about 3 years. Build a batch of comprehensive pipe gallery projects for small and medium-sized cities according to local conditions. The underground pipeline of newly built roads, new urban areas and various parks shall be developed and constructed in accordance with the comprehensive pipeline gallery.

As time goes by, the State Council further requires that the underground comprehensive pipe gallery should be constructed when all kinds of newly built roads are paved according to functional requirements in order to solve the repeated paving of roads caused by pipeline laying. For old urban areas, increase the construction of underground comprehensive pipe gallery at an appropriate time, combined with gradually updated underground pipelines. It is necessary to focus on the application of underground space and build a comprehensive pipeline gallery for high-density population areas, roads and areas with great traffic flows and dense underground pipelines as the city expands. At the same time, it is clearly required in the guiding opinions to promote the gallery of natural gas pipelines.

In March 2018, in the meeting of the 2nd Pipe Gallery Conference, the experience and achievements of construction of the underground pipe gallery were summarized during the Twelfth Five-Year Plan period, and the developmental direction of the construction of underground pipe gallery during the 13th Five-Year Plan period was proposed. Although the comprehensive pipeline gallery requires a lot of manpower, material resources and other resources in the initial construction of the pipeline project, it performs well in the later operation and maintenance. It not only increases the accuracy of daily inspection, but also provides great convenience in the repair of the pipeline. There is no need to damage the road surface, and the operation time of the construction is not restricted by traffic conditions. The GB50838-2015 Technical Specifications for Urban Comprehensive Pipe Gallery Engineering stipulates the material and connection method of natural gas pipelines entering the gallery; seamless steel pipes and welded connections should be adopted. In the pipe gallery environment, several common corrosion factors for buried pipelines are greatly reduced. Under this circumstance, on the premise of ensuring safety and considering the economics of the project, whether it is possible to use Q345D and L290M straight seam steel pipes with a higher grade of material instead of 20 steel seamless steel pipes.

A comprehensive comparison of seamless steel and welded steel pipe galleries
The pipes in the pipe gallery are not troubled by soil corrosion. Laying pipelines on pipe racks in the pipe gallery is similar to overhead pipelines, so the main failure factors are hoop stress and radial stress. As the service life of the pipeline increases, the pipeline will deform, and upward force will be generated at the fulcrum of the pipe frame; the pipeline itself will generate downward force under the influence of gravity. If things go on like this, stress concentration will occur at the pipeline's welding part. The tensile strength of 20 steel is the smallest, Q345D medium, and L290M greatest. Under the influence of gravity, L290M is the least affected. The experiments at the welded joints also show that L290M has the best hardness in the fusion zone and heat-affected zone, and the internal structure of the welded joint is evenly distributed and can withstand great tensile stress. Although the seamless steel pipe of 20 steel reduces the welding seam of the pipe itself in the pipe's manufacturing process, the welding performance of the material is not as good as the other two materials.

From the manufacturing process, as long as the qualified materials are selected, the probability of problems with the welding seam of the pipe itself can still be greatly reduced. However, there is only a theoretical possibility for material substitution at present, and a lot of experiments are required for practical applications based on safety considerations. Compare the construction in the pipe gallery with that of overhead pipelines, the construction method of the pipeline is the same no matter what kind of material is used. Therefore, the economy is mainly reflected in the price gap. The seamless pipe is formed once by rolling, which has smooth internal surfaces and can withstand higher pressure, but the production cost is high. The welded steel pipe is welded after the steel plate is rolled. High-frequency welded steel pipes have good plasticity, lower manufacturing costs, good pressure-bearing capacity, safe and reliable use, large pipe diameters, and good conveying capacity. Therefore, under the condition of the same wall thickness and pipe diameter, the price of the welded pipe is lower than that of the seamless pipe. In terms of the material's performance, L290M can theoretically replace 20 steel.

Summary
Speaking of medium and low pressure buried gas pipelines, PE pipes are suitable for pipelines below DN200. Centrifugal ductile iron pipes are good for pipelines with sizes between DN200 to DN400, and 3PE anticorrosive steel pipes are applied to pipelines above DN400. In the construction of the pipe gallery, because there is no soil corrosion environment, the failure of the pipeline is mainly caused by the influence of external stress. The cost of seamless pipes is higher than that of welded pipes. Therefore, in the construction of medium and low pressure pipelines or pipes with large diameters, you can consider using welded steel pipes made from L290M with more uniform internal structure and better hardness and strength instead of seamless steel pipes made from 20 steel.

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Landee Pipe is a professional industrial pipe manufacturer based in China, we have been producing pipe for a variety of applications, and covering areas of pipe manufacturing, exporting and trading. welcome to access our website: https://www.landeepipe.com.

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