The production process of spiral steel pipes is characterized by its simplicity, high efficiency, and capability to produce welded pipes with larger diameters from material of a given size, as well as pipes with varying diameters from the same width of billet. However, compared to straight seam pipes of the same length, spiral welded pipes have a 30-100% longer weld seam and a lower production speed.
Smaller-diameter welded pipes are mostly produced through straight seam welding, while larger-diameter pipes typically utilize spiral welding. The applications of spiral steel pipes are diverse, primarily used in water supply projects, petrochemical, chemical, and power industries, agricultural irrigation, and urban construction. They are among the twenty key products developed in China. These pipes serve various purposes: for liquid transportation (water supply and drainage), gas transmission (gas, steam, liquefied petroleum gas), and structural applications (such as piling pipes, bridges, docks, roads, and building structures).
The main production process is outlined below:
Both internal and external welding employ single-wire or double-wire submerged arc welding to ensure stable welding specifications. Process parameters are adjusted by production workers in real-time to promptly eliminate any defects.
Air plasma cutting machines are used to cut the steel tubes into individual lengths.
After cutting, the first three tubes from each batch undergo a rigorous initial inspection process, including testing the mechanical properties, chemical composition, fusion status, surface quality of the steel tubes, and non-destructive flaw detection. Only after confirming that the pipe-making process meets the standards can production commence.
Sections of the weld seam marked for continuous acoustic flaw detection undergo manual ultrasonic and X-ray re-inspections. In case of defects, repairs are made, followed by another non-destructive inspection until the defects are confirmed to be eliminated.
All pipes containing butt welds of steel strips and T-joints intersecting with spiral welds undergo X-ray television inspection or radiography.
Each steel pipe undergoes a hydrostatic pressure test with radial sealing. The test pressure and duration are strictly controlled by a steel pipe hydrostatic pressure microcomputer testing device. Test parameters are automatically printed and recorded.
Mechanical processing of the pipe ends ensures precise control over end face perpendicularity, groove angle, and root face.
