Large-diameter spiral welded pipes have a diameter greater than 400 mm and can even reach several meters in width. Spiral steel pipes are made by bending and forming steel strip coils, followed by welding. This type of steel pipe, with its unique spiral weld seam, possesses high strength and rigidity. Furthermore, the spiral weld seam is more uniform and has a more reasonable stress distribution than a straight seam weld seam.
Large-diameter spiral welded pipe production process:
Spiral steel pipes are made from steel strip coils as raw materials, formed by cold extrusion, and welded using an automatic double-wire double-sided submerged arc welding process. The main production process is as follows:
- Raw materials, namely steel strip coils, welding wire, and flux, must undergo strict physical and chemical testing before being used.
- The ends of the steel strip are butt-welded using single-wire or double-wire submerged arc welding. After being rolled into a steel pipe, automatic submerged arc welding is used for additional welding.
- Before forming, the steel strip undergoes leveling, edge trimming, edge planing, surface cleaning, conveying, and pre-bending. (4) The pressure of the hydraulic cylinders on both sides of the conveyor is controlled by an electric contact pressure gauge, ensuring smooth conveying of the strip steel.
- External or internal control roller forming is used.
- A weld gap control device is used to ensure that the weld gap meets welding requirements; pipe diameter, misalignment, and weld gap are all strictly controlled.
- Both internal and external welding use Lincoln Electric welding machines from the USA for single-wire or double-wire submerged arc welding, thus obtaining stable welding specifications.
- All welded seams are inspected by an online continuous ultrasonic automatic flaw detector, ensuring 100% non-destructive testing coverage of the spiral welds. If defects are found, an automatic alarm is triggered and a mark is sprayed, allowing production workers to adjust process parameters and eliminate defects promptly.
- An air plasma cutting machine is used to cut the steel pipe into individual pieces. (10) After being cut into individual steel pipes, the first three pipes of each batch undergo a strict first-pass inspection system. This includes checking the mechanical properties, chemical composition, fusion status, and surface quality of the weld, as well as non-destructive testing to ensure the pipe manufacturing process is up to standard before formal production can begin.
- Areas with continuous ultrasonic flaw detection marks on the weld are manually inspected using ultrasonic and X-ray methods. If defects are found, they are repaired and then subjected to non-destructive testing again until the defects are confirmed to be eliminated.
- All pipes containing butt welds of the strip steel and T-joints intersecting with spiral welds are inspected using X-ray television or radiography.
- Each steel pipe undergoes a hydrostatic pressure test, with radial sealing applied. The test pressure and time are strictly controlled by a computer-controlled hydrostatic pressure testing device. Test parameters are automatically printed and recorded.
- Pipe ends are machined to ensure accurate control of end face perpendicularity, bevel angle, and blunt edge.
Advantages:
- High Pressure Resistance: Due to its unique spiral weld structure, stress is distributed relatively evenly throughout the pipe body, enabling the pipeline to withstand high internal and external pressures, resulting in high safety.
- Flexible Specifications: Compared to steel pipes manufactured using other processes, spiral welded pipes offer greater flexibility in diameter and wall thickness adjustment, allowing for the production of non-standard products tailored to project requirements.
- High Strength and Long Service Life: Using high-quality steel as raw material and undergoing rigorous production processes and anti-corrosion treatment, the finished pipelines possess high structural strength and a long service life, adapting to various complex geological and climatic environments.
- Economical Advantages: Under the premise of meeting the same performance requirements, large-diameter spiral steel pipes often offer better economic efficiency in manufacturing and installation costs, which is crucial for controlling the total investment of large-scale projects.
Applications of Large-Diameter Spiral Steel Pipes
- Water Conservancy Projects: Water diversion pipelines for large reservoirs, water transmission pipelines for pumped-storage power stations, etc.
- Ports and Wharves: Large pipelines used for dredging and transporting materials.
- Structural Support: Also used as pile pipes or structural pipes in some large-scale building or bridge projects.
- Thermal Power Projects: Power plant circulating water pipelines, fly ash conveying pipelines, etc.
Large-Diameter Spiral Steel Pipes factory
