Massive procurement of national-standard large-diameter spiral steel pipes

Large-diameter spiral steel pipes refer to spiral steel pipes with a nominal diameter of DN850 or greater. The primary raw material used in their production is strip steel. Spiral steel pipes generally have higher strength than straight-seam welded pipes, allowing for the manufacture of larger‑diameter pipes from narrower billets, and enabling the production of pipes with different diameters from billets of the same width. Large‑diameter spiral steel pipes are manufactured using double‑sided submerged arc welding, which offers advantages such as stable weld quality, high welding productivity, minimal arc radiation, and reduced fumes and dust. Key parameters include outer diameter, wall thickness, and length. Mechanical tests typically encompass hydrostatic pressure testing, bending tests, and flattening tests. The applicable standards include: SY/T 5037-2008 (a ministry standard, also known as spiral seam submerged arc welded steel pipe for general fluid conveyance); GB/T 9711.1-2008 (a national standard, also referred to as steel pipe for oil and gas transportation); API 5L (American Petroleum Institute standard, also called pipeline steel pipe); SY/T 5040-2008 (spiral seam welded steel pipe for pile applications); and SY 5039-2000 (general low‑pressure fluid transport spiral seam high‑frequency welded steel pipe). The main grades used are Q235A, Q235B, 20#, Q345 (16Mn), and pipeline steels ranging from X42 to X70. Their primary applications include: liquid transport—such as water supply and drainage; gas transport—such as coal gas, steam, and liquefied petroleum gas; and structural uses—such as piling tubes, bridge construction, and piping for docks, roads, and building structures. Below is a brief overview of several types of welded pipes and their applications: 1. General welded pipes are used for conveying low‑pressure fluids such as water, coal gas, air, oil, and heating steam. 2. Ordinary carbon steel conduit pipes (GB 3640-88) are steel tubes employed in electrical installation projects—such as industrial and civil buildings and machinery installations—to protect electrical wires. 3. Straight‑seam electric welded pipes (YB 242-63) are steel pipes whose weld seams run parallel to the longitudinal axis of the pipe. They are commonly categorized into metric electric welded pipes, thin‑walled electric welded pipes, transformer cooling oil pipes, and others. 4. Spiral seam submerged arc welded pipes for pressurized fluid conveyance (SY 5036-83) are manufactured by rolling hot‑rolled steel strips into pipe blanks, forming them into spirals at room temperature, and then welding them using double‑sided submerged arc welding. These pipes are designed for transporting pressurized fluids, offering strong pressure resistance, excellent weldability, and proven safety through rigorous scientific inspections and tests. With large diameters and high conveying efficiency, they help reduce capital costs associated with pipeline installation. They are primarily used for oil and natural gas pipelines. 5. Spiral seam high‑frequency welded pipes for pressurized fluid conveyance (SY 5038-83) are produced by rolling hot‑rolled steel strips into pipe blanks, forming them into spirals at room temperature, and welding them using high‑frequency lap welding. These pipes exhibit strong pressure resistance, good ductility, and ease of welding and shaping. After undergoing stringent scientific inspections and tests, they demonstrate reliable performance, large diameters, and high conveying efficiency, while also reducing pipeline installation costs. They are mainly used for laying pipelines that transport oil and natural gas. 6. General low‑pressure fluid transport spiral seam submerged arc welded pipes (SY 5037-83) are manufactured by rolling hot‑rolled steel strips into pipe blanks, forming them into spirals at room temperature, and employing either double‑sided automatic submerged arc welding or single‑sided welding techniques. These pipes are specifically designed for conveying low‑pressure fluids such as water, coal gas, air, and steam.

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