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Technical Articles
Manufacturing Process of Welded Pipes with Large Diameters and Production Process of LSAW Pipes
Posted: 05/05/2017 14:10:25  Hits: 28
With the development of China's national economy, large-diameter LSAW pipes are more and more welcomed by oil and gas, ore pulp transportation and steel structure engineering industries due to the advantages of strong bearing ability, low resistance, low temperature resistance, corrosion resistance and easy installation. 

Description of main production processes of large diameter LSAW pipes
1.Ultrasonic Testing: Use ultrasonic testing for steel plates used for making large-diameter LSAW pipes after they are put into the production line.

2.Edge Milling: Use a milling machine to mill both sides of the steel plate so as to achieve the required plate width, parallelism of the plate edge and groove shape.

3.Pre-bending: Use a pre-bending machine to prebend the plate edge in order to meet the required curvature.

4.Shaping: Use a JCO shaping machine to stamp half of the pre-curved steel plate, pressing it into a "J" shape, then bend the other half of the steel plate, forming a "C" shape and an open "O" shape finally.

5. Pre-welding:  Joint the seam of shaped longitudinally welded pipe and use gas shielded welding (MAG) for continuous welding.

6.Internal Welding: Use multiple wire submerged arc welding for inner parts of the LSAW pipes.

7. External Welding: Use multiple wire submerged arc welding for external parts of LSAW pipes.

8.Ultrasonic InspectionⅠ: Use ultrasonic to 100% inspect the inner and outer welding seams and their base material on both sides of longitudinally welded pipes.

9. X-ray InspectionⅠ: Use 100% X-ray to inspect the internal and external welding seams and ensure the sensitivity of the inspection by using image processing system.

10. Expanding: Expand the full length of the LSAW pipe to improve its dimensional accuracy and distribution of internal stress.

11. Hydraulic Test: Check the expanding LSAW pipe one by one on the hydraulic testing machine so as to ensure that the LSAW pipe can meet the required testing pressure. Hydraulic testing machines have automatic recording and storage functions. 

12.Chamfering: Process the end of the qualified pipe to achieve the required groove size.

13. Ultrasonic TestⅡ: Use ultrasonic test to check LSAW pipes one by one, so that we can find out possible defects after expanding and hydraulic processes.

14. X-ray InspectionⅡ: Use X-ray to test LSAW pipes which are expanded and hydraulically tested and shoot X-ray film for the welding seams.

15. Pipe Ends Magnetic Particle Examination: Use magnetic particle examination to examine defects of pipe ends.

16.Anti-corrosion and Coating: Take treatment of corrosion and coating for the qualified steel pipe according to users’ requirements.

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