The spiral welded pipe mill is a standardized and mature equipment developed by Duolek Heavy Industry by integrating advanced foreign forming technologies with domestic practical conditions. It stands as one of Duolek’s most competitive and technologically distinctive production lines.

▶ Production Process of Spiral Welded Pipe Mill:
• Raw Materials: Steel coil, welding wire, and flux. All materials undergo rigorous physical and chemical inspections before use.
• Strip Head-Tail Butt Welding: Single or double-wire submerged arc welding is applied for strip head-tail joining. Automatic submerged arc welding is used for repair welding after coiling into pipes.
• Pre-Forming Treatment: The steel strip undergoes leveling, edge trimming, edge planing, surface cleaning, conveying, and pre-bending.
• Pressure Control: An electric contact pressure gauge controls the pressure of the hydraulic cylinders on both sides of the conveyor to ensure stable strip feeding.
• Forming Method: External or internal control roller forming is adopted.
• Weld Gap Control: A weld gap control device ensures precise welding gap requirements, with strict control over pipe diameter, misalignment, and weld gap.
• Internal/External Welding: Single or double-wire submerged arc welding using Lincoln electric welders (USA) ensures stable and consistent welding quality.
• Cutting: Pipes are cut into individual lengths using air plasma cutting machines.
• Strict Inspection: Each batch of pipes undergoes rigorous testing, including mechanical properties of welds, chemical composition, fusion quality, surface inspection, and non-destructive testing. Production begins only after passing all quality checks.

▶ Fully Automatic Hydrostatic Testing Machine
This machine conducts pressure tests on welded pipes, featuring computer-based recording, storage, printing, and result analysis. It offers high efficiency, high test pressure, and strong safety. It supports pipe diameters from Φ20 to Φ3500mm and test pressures from 10 to 110MPa.
Process Flow: Pipe loading → connection → water filling → pressure application → pressure holding → pressure release → water drainage → pipe unloading.

▶ Fully Automatic Pipe-End Facing and Chamfering Machine
Designed for pipe-end facing and chamfering, this machine uses profiling chamfering tools to ensure uniform and aesthetically pleasing grooves. The processing range covers pipe diameters from Φ20mm to Φ3500mm, complying with standards such as API-5L, API-5CT, BS1387-85, ASTM, and GB9711.
Process Flow: Pipe loading → connection → clamping → facing/chamfering → clamp release → pipe unloading.

▶ Ultrasonic Flaw Detector
• Automatic defect alarm and spray marking, enabling operators to adjust parameters accordingly.
• Sections marked with continuous ultrasonic inspection undergo manual ultrasonic and X-ray re-inspection.
• Defects are repaired and re-inspected via non-destructive testing until fully eliminated.

▶ X-ray Pipe Inspection System
Integrated seamlessly with the production line, this system meets the control and management requirements of pipe manufacturers. Key features include:
• Automatic weld seam recognition technology for streamlined inspection preparation.
• Database integration for one-click parameter retrieval and automatic loading of testing settings.
• High automation and operational efficiency, widely adopted in domestic pipe production lines.

▶ Applications of Spiral Welded Pipe Mill
The mill is widely used in high/low-pressure fluid transmission pipes, urban construction pile pipes, industrial structural pipes, and power/heat/gas pipelines, delivering efficient and high-quality piping solutions.