Longitudinally welded pipes are now widely used in many industries. Let's take a look at how they are manufactured.
Steel Plate Inspection: The steel plate is first subjected to an ultrasonic inspection to ensure its integrity before the submerged arc welding process for large-diameter pipe joints.
Edge Milling: Both edges of the steel plate are double-sided milled using a milling machine to meet the requirements for plate width, edge parallelism, and groove shape.
Pre-Bending: The plate edges are pre-bent using a pre-bending machine to achieve the required curvature.
Forming: On a JCO forming machine, the half-bent steel plate is pressed into a "J" shape through multiple steps, followed by bending the other half into a "C" shape, ultimately forming an open "O" shape.
Pre-Welding: Preparation for longitudinal welding of the pipe involves continuous gas welding (MAG).
Internal Welding: The inside of the longitudinally welded pipe is welded using a longitudinal multi-wire submerged arc welding process (not exceeding four wires).
External Welding: Longitudinal multi-wire submerged arc welding is also used for the external welding of the pipe.
Ultrasonic Inspection I: 100% inspection of the internal and external welds and the metal on both sides of the welds is conducted using ultrasonic technology.
X-Ray Inspection I: 100% X-ray inspection with industrial television is performed on the internal and external welds. An image data processing management system ensures the sensitivity of the inspection.
Diameter Expansion: The full length of the submerged arc welded pipe is expanded to improve dimensional accuracy and stress distribution within the pipe.
Hydrostatic Testing: Each expanded pipe is individually tested on a hydraulic testing machine to ensure it meets the standard test pressure. The machine has automatic recording and storage capabilities.
Chamfering: The inspected pipes are chamfered at the ends to meet the required groove dimensions for piping connections.
Ultrasonic Inspection II: A second ultrasonic inspection is conducted to detect any defects that may have occurred after diameter expansion and hydrostatic testing.
X-Ray Inspection II: An X-ray industrial inspection is performed on the pipe ends and weld seams after diameter expansion and hydrostatic testing.
Magnetic Particle Testing at Pipe Ends: This inspection is conducted to identify any defects present at the ends of the pipes.
