The production process of spiral welded pipes involves a series of precise and controlled steps to ensure high-quality output. First, the raw materials—such as strip coils, welding wire, and flux—are subjected to rigorous physical and chemical testing before being used in the manufacturing process.
Next, the ends of the steel strip are joined using single or double wire submerged arc welding. After the strip is rolled into a pipe, any imperfections are repaired using automatic submerged arc welding to maintain structural integrity.
Before forming, the steel strip undergoes leveling, trimming, planing, surface cleaning, and pre-bending to prepare it for the rolling process. An electric contact pressure gauge is used to regulate the pressure on both sides of the conveyor, ensuring smooth and consistent feeding of the strip.
The pipe is then formed using either external or internal control roll forming methods. A weld gap control device ensures that the gap between the edges meets the required specifications, while the pipe diameter, misalignment, and weld gap are all closely monitored during this stage.
Internal and external welding are performed using American Lincoln welding machines, which use single or double wire submerged arc welding techniques to achieve stable and reliable welds. This step is crucial for maintaining the strength and durability of the final product.
All weld seams are inspected using an online continuous ultrasonic automatic flaw detector, ensuring full coverage of the spiral welds. If any defects are detected, the system automatically alerts the operators and marks the affected area. Production workers can then adjust the process parameters in real time to address and eliminate the issue promptly.
Once the welding is complete, the steel pipe is cut into individual sections using an air plasma cutting machine. Each batch of pipes undergoes a strict first inspection, including checks on mechanical properties, chemical composition, weld fusion, surface quality, and non-destructive testing, to ensure compliance with quality standards before mass production begins.
Any welds that show signs of defects from the ultrasonic testing are manually re-examined using ultrasonic waves and X-ray imaging. If confirmed as defective, they are repaired and retested until the defect is fully resolved.
Pipes where the butt weld seam intersects with the spiral weld seam are inspected using X-ray television or filming to ensure no hidden flaws exist at these critical points.
Each steel pipe is also subjected to a hydrostatic pressure test, where the pipe is sealed radially and tested under controlled pressure and duration. The testing is managed by a microcomputer detection system that records and prints the results automatically.
Finally, the pipe ends are machined to ensure accurate control over the end face perpendicularity, bevel angle, and edge thickness, ensuring proper fit and performance when installed.
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