Spiral Steel Pipe

Spiral pipe, also known as spiral steel pipe or spiral welded pipe, is manufactured by rolling low-carbon structural steel or low-alloy structural steel strip into pipe blanks at a certain spiral angle (forming angle) and then welding the pipe seams. It enables the production of large-diameter steel pipes using relatively narrow steel strips.

# Production Process

(1) Raw materials, including steel strip coils, welding wires and fluxes, shall undergo strict physical and chemical inspections before being put into production.

(2) Single-wire or double-wire submerged arc welding is adopted for the butt joint of the head and tail of steel strips, and automatic submerged arc welding is applied for repair welding after the strips are rolled into steel pipes.

(3) Before forming, the steel strips are processed through flattening, edge shearing, edge planing, surface cleaning, conveying and pre-bending.

(4) Electric contact pressure gauges are used to control the pressure of the pressing oil cylinders on both sides of the conveyor, ensuring the stable conveying of steel strips.

(5) External or internal controlled roll forming is adopted.

(6) Weld gap control devices are equipped to ensure the weld gaps meet welding requirements, with strict control over pipe diameter, edge misalignment and weld gap.

(7) Both internal and external welding adopt single-wire or double-wire submerged arc welding with Lincoln electric welding machines from the United States to achieve stable welding specifications.

(8) All welded seams are inspected by an on-line continuous automatic ultrasonic flaw detector, realizing 100% non-destructive testing coverage of spiral welds. In case of defects, the device will give an automatic alarm and spray marks, allowing production workers to adjust process parameters in a timely manner and eliminate defects promptly.

(9) Steel pipes are cut into single pieces by air plasma cutting machines.

(10) After being cut into individual steel pipes, each batch shall undergo strict initial inspection, covering the mechanical properties, chemical composition and fusion condition of welds, surface quality of steel pipes and non-destructive testing. Formal delivery is only allowed after the pipe manufacturing process is confirmed qualified.

(11) Parts with continuous ultrasonic testing marks on welds shall be rechecked by manual ultrasonic testing and X-ray inspection. Any confirmed defects shall be repaired and re-inspected non-destructively until all defects are completely eliminated.

(12) Pipes with strip butt welds and T-joints intersecting with spiral welds shall all be inspected by X-ray television or radiographic testing.

(13) Each steel pipe is subjected to hydrostatic testing with radial sealing. The test pressure and holding time are strictly controlled by a microcomputer-based steel pipe hydraulic testing device, and test parameters are automatically printed and recorded.

(14) Mechanical processing is performed on pipe ends to precisely control the end face perpendicularity, bevel angle and root face.