Technical characteristics and advantages of LSAW steel pipes
As a high-performance steel pipe product, the manufacturing process and material science of LSAW steel pipes contain profound technical accumulation and innovative achievements. These characteristics make it the preferred material for long-distance natural gas transportation and urban pipeline construction. Unlike alternative products such as spiral welded pipes or high-frequency straight seam electric resistance welded pipes, LSAW steel pipes show significant advantages in pressure bearing capacity, dimensional accuracy and weld quality, and can meet the safe operation requirements of natural gas pipelines in harsh environments. A deep understanding of these technical characteristics and advantages will help engineering and technical personnel make more reasonable material choices in pipeline design and construction, and will also help to recognize the core value of LSAW steel pipes in the natural gas industry.

​​Excellent pressure bearing capacity is one of the most prominent technical features of LSAW steel pipes. Natural gas pipelines usually need to withstand higher transmission pressures. The working pressure of long-distance pipelines is generally between 6.3-12MPa, and the pressure of urban high-pressure ring networks may also reach more than 4.0MPa. LSAW steel pipes are made of high-quality medium and thick plates as raw materials, and are manufactured through precise JCOE or UOE forming processes and double-sided submerged arc welding technology. The longitudinal weld structure keeps the main stress direction consistent with the direction of the highest strength of the steel pipe. In contrast, the weld of the spiral welded pipe is distributed in a spiral shape, and its main stress direction is at a certain angle to the axial direction of the steel pipe, resulting in a relatively reduced pressure bearing capacity. Actual engineering data show that under the same material and wall thickness conditions, the pressure bearing capacity of LSAW steel pipes is 15%-20% higher than that of spiral welded pipes. This feature makes it particularly suitable for high-pressure and large-diameter natural gas transmission pipelines. For example, in the China-Russia East Line Natural Gas Pipeline Project, the X80 grade LSAW steel pipe used has a working pressure of 12MPa and a pipe diameter of 1422mm, which fully demonstrates the technical advantages of LSAW steel pipes under high pressure and large-diameter conditions.

​​Manufacturing process advantages: The production process of LSAW steel pipes incorporates many innovative achievements in modern steel processing technology. The typical LSAW steel pipe manufacturing process includes 16 main processes such as plate ultrasonic inspection, edge milling, pre-bending, JCO forming, pre-welding, internal and external multi-wire submerged arc welding, expansion, and water pressure testing. This refined process ensures the excellent performance of the final product. Among them, the double-sided submerged arc welding technology is the core guarantee of the quality of LSAW steel pipes. The longitudinal multi-wire welding (up to four wires) is used to weld the inside and outside of the steel pipe respectively, which not only greatly improves the welding speed and production efficiency, but more importantly, forms a high-quality weld with deep penetration and low defects. During the submerged arc welding process, the arc burns under the flux layer, avoiding the influence of the outside air on the welding quality. At the same time, the alloy elements in the flux can be transitioned to the weld metal to improve its chemical composition and mechanical properties. In addition, the expansion process in the LSAW steel pipe manufacturing process is also crucial. By mechanically expanding the entire length of the steel pipe, not only the dimensional accuracy of the steel pipe is improved, but also the distribution state of stress in the steel pipe is significantly improved, and the negative impact of residual stress on the pipeline performance is reduced.
​​In terms of dimensional accuracy and geometric characteristics, LSAW steel pipes also show obvious advantages. During the construction of natural gas pipelines, they need to face a complex on-site welding environment. The geometric dimensional accuracy of the steel pipe directly affects the quality and construction efficiency of the pipeline girth weld. LSAW steel pipes are formed by a single steel plate, with precision machining equipment and strict process control. Its diameter deviation, ovality, wall thickness uniformity and other indicators are better than spiral welded pipes. Taking the LSAW steel pipe with a diameter of 1420mm as an example, its diameter deviation can be controlled within ±0.5mm, and the ovality does not exceed 0.2%. This high-precision feature makes the on-site docking of pipelines more convenient and the quality of welds more guaranteed. In contrast, due to the limitations of the forming process, the diameter deviation of spiral welded pipes is usually around ±1.0mm, and the ovality may reach more than 0.5%. In addition, the straightness of LSAW steel pipes is also superior, with a straightness deviation of no more than 1mm per meter and a straightness deviation of no more than 0.1% of the length of the steel pipe. These characteristics greatly reduce the construction difficulty during pipeline laying, especially in trenchless operations such as directional drilling and pipe jacking construction. The high-precision characteristics of LSAW steel pipes are particularly important.
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