The process for producing spiral welded pipes involves several meticulous steps to ensure high-quality output:
(1) The raw materials, including strip coils, welding wires, and flux, undergo rigorous physical and chemical tests prior to use to guarantee their suitability.
(2) The strip ends are joined using either single or double-wire submerged arc welding, while post-rolling repairs are conducted via automated submerged arc welding techniques.
(3) Before forming, the strip is straightened, trimmed, planed, cleaned, and pre-bent to prepare it for further processing.
(4) An electric contact pressure gauge monitors and controls the cylinder pressures on both sides of the conveyor to maintain seamless strip conveyance.
(5) External or internal roll forming methods are employed depending on the specific requirements.
(6) A specialized weld gap control mechanism ensures precise alignment, carefully managing the pipe's diameter, misalignment levels, and weld gap dimensions.
(7) Both internal and external welds utilize advanced American Lincoln welding machines for single or double-wire submerged arc welding, ensuring consistent welding quality.
(8) All welds are examined using an online continuous ultrasonic automatic flaw detector. This guarantees comprehensive non-destructive testing of the spiral welds. Any detected defects trigger an automatic alert and marking spray, allowing operators to promptly adjust settings and resolve issues.
(9) Steel pipes are cut into individual pieces using an air plasma cutter.
(10) Following cutting, each batch of steel pipes undergoes a stringent initial inspection protocol, assessing mechanical properties, chemical composition, weld fusion integrity, surface quality, and non-destructive testing. Only after confirming compliance are the pipes approved for official production.
(11) Sections marked by continuous sonic flaw detectors are manually rechecked with ultrasonic waves and X-rays. Defective areas are repaired and retested until confirmed free of flaws.
(12) Areas where strip butt welds meet spiral welds are inspected through X-ray television or film imaging.
(13) Every pipe undergoes hydrostatic pressure testing. This is carried out under strict control of the test pressure and duration using a microcomputer-based detection system for steel pipes. Test data is automatically logged and printed.
(14) The pipe ends are machined to ensure precise control over end face perpendicularity, bevel angles, and edge thickness.
This detailed approach ensures that every stage of production adheres to stringent standards, resulting in reliable and durable spiral welded pipes.
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