The production process of spiral welded pipes involves a series of precise and controlled steps to ensure the quality and integrity of the final product. The raw materials, including steel strip coils, welding wires, and flux, must undergo rigorous physical and chemical testing before they are used in the manufacturing process.
Initially, the ends of the steel strip are joined using single or double wire submerged arc welding. Once the strip is formed into a pipe, any imperfections are repaired using automatic submerged arc welding. Before forming, the steel strip is leveled, trimmed, planed, cleaned, and pre-bent to prepare it for the next stage.
To maintain consistent pressure during the feeding process, an electric contact pressure gauge is used to regulate the pressure applied by the cylinders on both sides of the conveyor. This ensures smooth and stable material flow throughout the production line.
The forming process can be either externally or internally controlled using roll forming techniques. A weld gap control device is employed to ensure that the gap between the edges of the steel strip meets the required specifications, while also maintaining strict control over the pipe diameter, misalignment, and weld gap.
Both internal and external welding are performed using American Lincoln welding machines, which use single or double wire submerged arc welding to achieve consistent and high-quality welds. After welding, all seams are inspected using an online continuous ultrasonic automatic flaw detection system, ensuring full coverage of the spiral welds. If any defects are detected, the system automatically alarms and marks the affected area, allowing operators to adjust parameters in real time to eliminate the issue.
Once the welding is complete, the steel pipe is cut into individual sections using an air plasma cutting machine. Each batch of pipes undergoes a thorough first inspection, which includes checking mechanical properties, chemical composition, weld fusion quality, surface condition, and non-destructive testing results to ensure compliance with production standards.
Any sections with sonar flaw detection markings are manually re-examined using ultrasonic waves and X-rays. If defects are confirmed, the pipes are repaired and retested until all issues are resolved. Additionally, areas where the butt weld seam intersects with the spiral weld are inspected using X-ray television or filming to ensure structural integrity.
Each pipe is subjected to a hydrostatic pressure test, where it is sealed radially and tested under controlled pressure and time conditions using a microcomputer-based detection system. The test results are automatically printed and recorded for documentation purposes.
Finally, the pipe ends are machined to ensure accurate control of the end face perpendicularity, bevel angle, and edge thickness, meeting the required dimensional specifications for further processing or installation.
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