Double Submerged Arc Welded (DSAW) Straight-Seam Steel Pipe

Our DSAW (Double Submerged Arc Welded) straight-seam steel pipes are produced using the advanced JCOE cold-forming process integrated with high-precision double-sided submerged arc welding technology. By executing welding passes on both the interior and exterior of the seam, we achieve deeper weld penetration, robust alignment, and a stronger metallurgical bond.

These heavy-duty pipes are engineered specifically for high-pressure, critical-service environments, such as long-distance oil and gas transmission pipelines and heavy-duty offshore structural piling foundations.

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Key Features & Advantages

Double-Sided Welding: Internal and external welding passes are executed to significantly reduce the risk of weld defects, optimize structural integrity, and enhance overall high-pressure resistance.

Superior Weld Quality: 100% automated submerged arc welding ensures exceptionally smooth, uniform weld beads that meet the strictest criteria of the API 5L standard.

Large Diameter & Heavy Wall Configurations: Our production line is capable of manufacturing outer diameters up to 1422mm (56″) and wall thicknesses up to 60mm, satisfying extreme structural and fluid engineering requirements.

Stress Relief via Expansion: After welding, the entire pipe body undergoes cold mechanical expansion to guarantee precise dimensions, correct ovality, and eliminate internal residual welding stresses.

Technical Specifications & Material Grades

To ensure compliance with international oil, gas, and heavy infrastructure projects, our DSAW steel pipes are produced strictly to the following parameters:

Parameter	Specification Details
Standard Compliance	API 5L (PSL1/PSL2), ASTM A671, ASTM A672, EN10219
Material Grade	Gr.B, X42, X52, X60, X65, X70, X80, S355JR
Outer Diameter (OD)	406 mm to 1422 mm (16" to 56")
Wall Thickness (WT)	8.0 mm to 60.0 mm
Length Options	6.0 m to 12.5 m (Supports Fixed Length / Custom length specifications)
Surface Treatment	Bare (uncoated), Black Varnished, 3PE (Three-Layer Polyethylene), FBE (Fusion Bonded Epoxy) Coating, Anti-corrosion Oiled

Quality Assurance & Testing

To ensure 100% reliability in high-stress pipeline environments and heavy-duty applications, every single pipe undergoes a rigorous quality control process before shipment:
· UT & RT Testing: We perform full-length Ultrasonic Testing (UT) and industrial X-ray Radiographic Testing (RT) of the longitudinal weld seam to completely eliminate any internal flaws or defects.
· Hydrostatic Pressure Testing: Every pipe is tested under specified high pressure with standard holding times to guarantee zero-leakage security and verify pressure-bearing capacity.
· Independent Third-Party Inspection: We fully support and welcome on-site product inspections and testing verification by trusted international bodies including SGS, BV, or TUV.

Packaging & Delivery Services

We provide heavy-duty export packaging and specialized logistics planning to preserve the integrity of our pipes during ocean transit:
· End Protection: Beveled ends are cut to precise angles and fitted with heavy-duty plastic caps to protect the double-sided weld bevels from mechanical damage and corrosion during transit.
· Professional Ocean Loading: Pipe shipments are loaded using professional cargo handling schemes. We offer specialized loading in 40ft Flat Rack (FR) containers or bulk cargo vessels to prevent surface scratches and structural deformation during maritime shipping.

Frequently Asked Questions (FAQ)

Q: What is a DSAW steel pipe, and what are its main advantages?

A: DSAW stands for Double Submerged Arc Welded steel pipe. The “Double” means the welding is executed on both the inside and the outside of the pipe body. This process utilizes a granular flux to submerge the welding arc, protecting the weld pool from atmospheric contamination. The main advantages include exceptionally deep weld penetration, uniform and smooth weld beads, and superior mechanical joint strength, making it ideal for critical high-pressure line pipe applications.

Q: What is the difference between DSAW and LSAW steel pipes?

A: LSAW (Longitudinal Submerged Arc Welding) refers specifically to the geometric shape of the weld seam, which runs straight and parallel to the pipe length. DSAW, on the other hand, defines the welding method (welded inside and out). In fact, most modern LSAW pipes are manufactured using the DSAW process (often called LSAW-DSAW). However, DSAW can also apply to spiral welded pipes (SSAW-DSAW). We supply high-quality longitudinal DSAW pipes for heavy-duty structural and energy projects.

Q: How do you prevent welding defects and ensure perfect alignment of inner and outer welds?

A: Alignment and penetration are critical for DSAW. We utilize advanced automatic laser tracking systems to ensure that the outer weld seam perfectly centers over the inner weld seam. Furthermore, we maintain a strict quality control workflow including online continuous Ultrasonic Testing (UT), followed by 100% industrial X-ray Radiographic Inspection of the weld seam to completely eliminate defects like porosity, slag inclusion, or incomplete fusion.

Q: What size configurations and pressure ratings do you offer for DSAW piping?

A: Our DSAW production lines are built for large-scale, heavy-wall requirements. We offer Outside Diameters (OD) spanning from 18″ to 60″ (457mm to 1524mm) with Wall Thicknesses (WT) up to 50mm. These heavy-wall DSAW pipes are manufactured in strict compliance with API 5L (PSL1 & PSL2) and ASTM A672, capable of handling high-pressure oil, gas transmission, and demanding structural dynamic loads.

Q: What mechanical and destructive tests are performed to verify DSAW seam strength?

A: To guarantee absolute reliability under project loads, we perform rigorous mechanical testing in our CNAS-certified laboratory. This includes Tensile Testing (verifying yield and tensile strength of the weld joint), Guided Bend Testing (checking weld ductility), and Charpy V-Notch Impact Testing (verifying toughness under low temperatures). All test records are fully detailed in the provided EN 10204 3.1 Mill Test Certificate (MTC).