Production process of steel plate spiral pipes

Release date:

2021-10-08

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Steel Pipe Knowledge

Prior to layout for steel‑plate coiled pipe fabrication, the steel plates must be inspected and aligned using a steel tape measure, and the layout dimensions shall be calculated based on the coil’s nominal diameter. Following layout, punch holes in the steel plates using a template and mark the plate’s centerline. Grooving of the pipe edges shall be performed by mechanical means; thermal processes such as plasma arc or oxy‑acetylene flame may also be employed.

　　 Steel plate rolled pipe Prior to layout, the steel plate must be checked and aligned using a steel tape measure, and the layout dimensions shall be calculated based on the coil’s nominal diameter. After layout, use a template to punch holes in the steel plate and mark its centerline. Pipe groove preparation shall be performed by mechanical means; thermal processes such as plasma arc or oxy‑acetylene flame may also be employed.

　　Prior to flame cutting, rust and oil shall be removed from the steel surface within a 50‑mm-wide zone along the cut edge. After grooves are formed by hot‑working, any scale, slag, or surface layer that could compromise joint quality must be thoroughly cleaned away; uneven areas shall be ground smooth. The cut surface shall be free of cracks and shall not exhibit edge defects exceeding 10 mm in length. Following cutting, oxides, weld beads, and spatter on the edges must be removed, and the machined surface shall be free of step differences.

　　The groove for jointing shall be machined in accordance with process requirements and relevant standards. For thin plates, a V‑groove is generally used; for thick plates, an X‑groove is employed. For plates thinner than 6 mm, grooves may be omitted; however, when welding on the reverse side, brickwork must be constructed and the root cleaned. When the edge of the groove or notch measures 1 to 3 mm, it may be machined or ground smooth, but the deviation shall not exceed 1/10 of the nominal thickness. If the edge or groove is chipped by more than 30 mm, it shall be repaired by overlay welding using low‑hydrogen electrodes of φ 3.2 or smaller, followed by grinding to achieve a smooth finish.

　　If delamination cracks appear at the edges of notches or grooves, use a magnifying glass or ultrasonic testing to measure the crack length and depth at least ten times. When the length a and depth d are both within 50 mm, extend 15 mm beyond each end of the crack, then machine the area into a groove using chisels, arc gouging, or grinding wheels, followed by repair welding with φ 3.2 low‑hydrogen electrodes and subsequent smooth grinding. If the depth d exceeds 50 mm or the cumulative length surpasses 20% of the plate width, in addition to the aforementioned methods, further slotting or drilling on the plate surface is required, along with the addition of plug welds.

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