1. Prospecting: Once the steel plate intended for manufacturing large-diameter SAW (Submerged Arc Welded) straight-seam steel pipes enters the production line, a full-plate ultrasonic inspection is conducted to ensure material quality and detect any internal flaws.
2. Milling: The edges of the steel plate are double-sided milled using a milling machine to achieve the required width, edge parallelism, and groove geometry, ensuring precise alignment during the forming process.
3. Pre-crimping: A pre-bending machine is used to shape the edges of the steel plate, giving them the necessary curvature to facilitate smooth forming in the next stage.
4. Forming: In the JCO forming machine, the pre-bent steel plate is first punched and pressed into a "J" shape. Then the other half is bent and pressed into a "C" shape, creating an open "O" configuration, which forms the basic structure of the pipe.
5. Pre-welding: The formed steel pipe is seam-welded using gas shielded metal arc welding (MAG), providing a preliminary weld that ensures structural integrity before final welding.
6. Internal Welding: The inside of the straight-seam steel pipe is welded using vertical multi-wire submerged arc welding, with up to four wires used simultaneously to ensure a strong, consistent weld.
7. External Welding: The outer surface of the LSAW steel pipe is welded using multi-wire submerged arc welding, enhancing the strength and durability of the weld.
8. Ultrasonic Inspection I: A 100% ultrasonic test is performed on both the internal and external welds, as well as the base metal adjacent to the weld, to detect any potential defects or inconsistencies.
9. X-ray Inspection I: A 100% X-ray industrial television inspection is carried out on the internal and external welds, utilizing an advanced image processing system to ensure high detection sensitivity and accuracy.
10. Expansion: The steel pipe undergoes diameter expansion to improve dimensional accuracy and optimize the distribution of internal stresses, resulting in a more uniform and stable product.
11. Hydrostatic Pressure Test: The expanded steel pipe is subjected to a hydrostatic pressure test on a dedicated testing machine to verify that it can withstand the required pressure. This machine automatically records and stores all test data.
12. Beveling: After passing all inspections, the ends of the pipe are beveled to meet the specified groove dimensions, preparing the pipe for final joining.
13. Ultrasonic Inspection II: Another round of ultrasonic testing is conducted to check for any possible defects that may have occurred during the expansion and pressure testing phases.
14. X-ray Inspection II: An X-ray industrial television inspection is performed on the pipe ends and weld seams after expansion and pressure testing, ensuring complete weld integrity.
15. Magnetic Particle Inspection: This non-destructive testing method is applied to the tube ends to identify any surface or near-surface defects that might affect performance.
16. Anti-Corrosion Coating: Finally, the qualified steel pipe is coated with anti-corrosion materials according to the customer's specifications, ensuring long-term durability and protection against environmental factors.
Gate Valves,Sea Water Gate Valve,Stainless Steel Gate Valve,Steel Gate Valve
ZHITONG PIPE VALVE TECHNOLOGY CO.,LTD , https://www.ztongvalve.com