Big diameter heavy wall thickness welded steel pipe LSAW

The production of Longitudinal Submerged Arc Welded (LSAW) steel pipes involves forming steel plates into a cylindrical shape and welding the longitudinal seam using the submerged arc welding (SAW) process. Below is a detailed step-by-step production process along with the main equipment used:

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• 1. Raw Material Preparation

  -Steel Plate Inspection:  

    - The process starts with checking the steel plates (usually API 5L, ASTM A36, or equivalent grades) for dimensions, chemical composition, and surface defects.

  -Edge Milling (Optional):  

    - Plates may undergo edge milling to ensure smooth, straight edges for better welding quality.

  Equipment:  

  - Ultrasonic testing (UT) machines  

  - Plate edge milling machines

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2. Plate Bending (JCO or UOE Forming)
The plate is bent into a cylindrical shape using one of the following methods:

a) JCO Forming (Step-by-Step Bending)
   -Joggle (pre-bending the edges)  
   -Closing (gradual bending into a C-shape)  
   -Opening (final pressing into an O-shape)  

b) UOE Forming (More Automated)
   -U-pressing (first bend into a U-shape)  
   -O-pressing (final pressing into an O-shape)  
   -Expanding (optional, for precise roundness)  

Equipment:  
- Hydraulic press (JCO/UOE press)  
- Plate pre-bending machine  
- Edge crimping machine  

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3. Welding (Longitudinal SAW)
-Internal Welding:  
  - Submerged Arc Welding (SAW) is performed on the inside of the pipe.  
  - A flux layer covers the arc to prevent oxidation.  
-External Welding:  
  - The pipe is rotated, and SAW is applied on the outside seam.  
  - Multi-pass welding ensures high strength.  

Equipment:  
- Submerged Arc Welding (SAW) machines (internal & external)  
- Welding wire and flux feeding system  

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4. Seam Inspection & Testing
-Non-Destructive Testing (NDT):  
  -Ultrasonic Testing (UT) – Detects internal defects.  
  -Radiographic Testing (RT) – X-ray inspection for weld integrity.  
  -Magnetic Particle Inspection (MPI) – Checks surface cracks.  

Equipment:  
- Ultrasonic flaw detectors  
- X-ray or gamma-ray inspection systems  

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5. Pipe Expansion (Optional)
-Cold Expansion:  
  - The pipe is expanded hydraulically to improve roundness and dimensional accuracy.  

Equipment:  
- Pipe expander machine  

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6. Cutting & Beveling
- The pipe is cut to the required length using a saw or plasma cutter.  
- Beveling is done at the ends for field welding compatibility.  

Equipment:  
- Pipe cutting saws  
- Beveling machines  

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7. Hydrostatic Testing
- The pipe is filled with water and pressurized to check for leaks or weak points.  

Equipment:  
- Hydrostatic test pumps & pressure monitoring systems  

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8. Final Inspection & Coating
-Dimensional Check: Diameter, wall thickness, straightness.  
-Surface Coating (Optional): Anti-corrosion coatings (e.g., 3LPE, FBE) may be applied.  

Equipment:  
- Coating application systems (spray or dipping)  
- Ultrasonic thickness gauges  

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9. Marking & Storage
- Pipes are marked with specifications (grade, size, heat number, etc.).  
- Stored in a warehouse before shipment.  

Equipment:  
- Paint marking machines  
- Pipe handling cranes  

Main Production Equipment Summary

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Final Notes
- LSAW pipes are widely used in oil & gas pipelines,structural applications, and water transmission due to their high strength and reliability.  
- The JCO method is cost-effective for medium-volume production, while UOE is more automated for high-volume output.  

Simple Flow Chart as follows:
[Steel Plate] → [Inspection] → [Edge Prep] → [JCO/UOE Forming] → [SAW Welding]  → 
[Weld Inspection] → [Expansion] → [Cutting] → [Hydro Test] → [Coating] → [Marking] → [Finished Pipe]