Spiral pipes, also known as spiral steel pipes or spiral welded pipes, are manufactured by rolling low-carbon structural steel or low-alloy structural steel strips into a pipe billet at a specific spiral angle (known as the forming angle) and then welding the seam together. They enable the production of large-diameter steel pipes from relatively narrow steel strips.
Applications:
Spiral pipes are primarily used in oil and natural gas transmission pipelines. Their specifications are expressed in terms of outer diameter * wall thickness. Spiral pipes come in both single-sided and double-sided welded varieties, and the welded pipes must ensure that their hydraulic pressure test, tensile strength of the weld seam, and cold bending performance meet the prescribed standards.
Production Process:
Raw materials, including steel strip coils, welding wires, and fluxes, undergo rigorous physical and chemical inspections before being put into use.
The steel strip heads and tails are butt-welded using single- or double-wire submerged arc welding, followed by automatic submerged arc welding for seam repairs after the pipe is rolled.
Before forming, the steel strip undergoes leveling, trimming, edge planing, surface cleaning, conveying, and pre-bending.
Electric contact pressure gauges control the pressure of the press cylinders on both sides of the conveyor, ensuring smooth steel strip transportation.
External or internal roll forming is employed.
A weld gap control device is used to ensure that the weld gap meets welding requirements, with strict control over pipe diameter, edge mismatch, and weld gap.
Both internal and external welding employs Lincoln Electric welding machines for single- or double-wire submerged arc welding, achieving stable welding specifications.
Completed weld seams undergo continuous online ultrasonic automatic flaw detection, ensuring 100% coverage of non-destructive testing for spiral welds. In case of defects, automatic alarms are triggered, and marks are sprayed for production workers to adjust process parameters promptly and eliminate defects.
Air plasma cutting machines are used to cut steel pipes into individual lengths.
After cutting, each batch of steel pipes undergoes rigorous initial inspection, checking the mechanical properties, chemical composition, fusion status of the weld seam, surface quality of the steel pipe, and non-destructive flaw detection to ensure the pipe-making process is qualified before formal production commences.
Areas with continuous sonic flaw detection marks on the weld seam undergo manual ultrasonic and X-ray re-inspections. If defects are confirmed, repairs are made, followed by non-destructive inspections until the defects are eliminated.
All steel pipes with butt welds 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. Test pressure and duration are strictly controlled by a steel pipe hydrostatic pressure microcomputer testing device, with test parameters automatically printed and recorded.
Mechanical processing of pipe ends ensures accurate control of end face perpendicularity, groove angle, and root face.
