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DSAW is a commercial term for steel pipe whose longitudinal or helical weld seam is submerged-arc welded from both the inside and outside. “Double” describes the two-sided welding arrangement rather than the number of seams.
Understanding its production and inspection helps buyers distinguish DSAW from SAWL, SAWH and ERW pipe. The sections below explain these differences, common applications and the specifications to confirm before ordering.
What Is DSAW Pipe?
DSAW stands for double submerged-arc-welded. Submerged arc welding uses a continuously fed electrode beneath granular flux, which shields the molten weld pool and forms slag over the cooling weld.
DSAW is common commercial terminology, while product specifications generally identify the manufacturing route as SAWL or SAWH. Under API 5L and ISO 3183, SAWL pipe has one or two longitudinal seams, whereas SAWH pipe has one continuous helical seam and is also commercially known as SSAW or HSAW.
DSAW production is commonly considered for large diameters and substantial wall thicknesses. Its pressure or structural capacity still depends on the grade, dimensions, weld procedure, inspection results and governing design requirements. Buyers can compare the main product categories in BAOLAI’s welded steel pipe range.
How Is DSAW Pipe Produced?
DSAW pipe is produced by preparing plate or coil, forming it into a cylinder and welding each seam from both surfaces. The pipe is then sized, finished and inspected according to the applicable specification.
Material Preparation and Edge Forming
Production begins with steel plate, strip or coil that meets the ordered chemical, mechanical and dimensional requirements. Material identification should remain traceable to the relevant heat and production batch.
The edges are trimmed or milled to control width and joint geometry. Thicker material may require a prepared groove to achieve the specified penetration and fusion.
Longitudinal production commonly uses UOE, JCOE or roll forming. Helical production feeds coil or strip through angled rolls to create a continuous spiral joint.
Pipe Forming and Tack Welding
Forming equipment brings the prepared edges together while controlling diameter, roundness and alignment. Longitudinal pipe is pressed or rolled from plate, while helical pipe is formed continuously from coil or strip.
Where tack welding is used, it holds the formed edges before final submerged arc welding. The tack-welding method, root gap and edge offset must follow the approved manufacturing procedure and applicable product specification.
Internal and External Submerged Arc Welding
Each seam is welded from both surfaces using submerged arc welding. One side is welded first, followed by the other according to the qualified procedure. The deposits fuse within the same joint region.
“Double” does not limit production to two passes or two welding heads. Mills may use single-wire, tandem-wire or multi-wire systems, while thick joints may require several passes. Current, voltage, travel speed, wire and flux are controlled to achieve the specified weld properties.
Weld repairs, where permitted, must follow an approved procedure and receive the required re-examination.
Sizing and Final Finishing
Sizing controls outside diameter, ovality and straightness. Longitudinal pipe may be mechanically expanded, while other routes can use sizing rolls or different calibration methods.
The pipe is cut to length and supplied with plain, square-cut or beveled ends as specified. Finishing may also include cleaning, coating, lining, marking and end protection, depending on the intended service and purchase order.
How Are DSAW, LSAW, SSAW and ERW Related?
These terms classify pipe on different bases. DSAW is a commercial descriptor for welding from both sides. LSAW and SSAW combine seam direction with submerged arc welding, while ERW identifies another welding process.
| Term | Classification Basis | Seam Direction | Welding Process | Common Production Focus |
| DSAW | Welding from both sides of the seam | Longitudinal or helical | Submerged arc welding with inside and outside weld passes | Large-diameter welded pipe, subject to the applicable product standard |
| LSAW or SAWL | Longitudinal seam; SAWL is the standards-based designation | Longitudinal | Submerged arc welding | Line pipe, pressure pipe and structural pipe where specified |
| SSAW, HSAW or SAWH | Helical seam; SAWH is the standards-based designation | Helical | Submerged arc welding | Line pipe, water pipe, piling and structural sections where specified |
| ERW or HFW | Electric-welded pipe; HFW is the high-frequency type | Longitudinal | Resistance or induction welding; ISO defines HFW at 70 kHz or above | Line, general-service and structural pipe, depending on the product standard |
An SAWL or SAWH product may be described commercially as DSAW when each seam is welded from both sides. DSAW is therefore not automatically synonymous with LSAW.
ERW forms its seam by electrically heating the strip edges and pressing them together. It does not normally use granular flux or a submerged filler-wire arc.
How Is DSAW Pipe Inspected?
Inspection commonly combines dimensional checks, weld examination, pressure or mechanical testing, and document review. The methods and acceptance criteria depend on the product standard, intended service and purchase order.
Weld Appearance and Dimensional Inspection
Visual inspection checks the internal and external welds for unacceptable undercut, overlap, irregular reinforcement and other visible imperfections. The pipe body is also examined for dents, cracks or forming damage.
Dimensional checks may cover outside diameter, wall thickness, ovality, straightness, length, end squareness and weld profile. Acceptance limits must follow the ordered specification rather than general mill practice.
Nondestructive Examination of Welds
Automated ultrasonic testing is commonly used along the weld and heat-affected zone. Where radiographic testing is specified, its method and coverage—including full-seam, pipe-end, selected-area or repair examination—follow the product standard and purchase requirements. ISO 10893-6 covers film-based radiography, while ISO 10893-7 covers digital radiography.
Magnetic-particle or liquid-penetrant testing may be specified for surface-breaking imperfections. Buyers should define the method, coverage, acceptance criteria and personnel qualification rather than request only “NDT tested” pipe.
Hydrostatic and Mechanical Testing
Hydrostatic testing verifies that finished pressure pipe sustains the specified test pressure for the required holding period without leakage. Test conditions and permitted alternatives depend on the applicable standard, dimensions, grade and intended service; structural pipe may follow a different testing programme.
Mechanical testing may include parent-metal and weld tensile tests, guided-bend tests, Charpy impact tests and, where specified for line-pipe service, drop-weight tear tests. The required tests and sampling frequency depend on the product standard, grade and service condition.
Hydrostatic testing does not replace weld examination or mechanical testing. Each evaluates a different aspect of conformity.
Traceability and Inspection Documents
Traceability connects each pipe to its raw material and production records. Markings may include the heat number, pipe number, standard, grade, dimensions and manufacturer identification.
The document package can include material certificates, dimensional reports, NDT records, hydrostatic test results and mechanical test reports. EN 10204 inspection certificates 3.1 or 3.2 may be requested when that documentation system applies.
BAOLAI’s steel pipe manufacturing process overview provides additional information on forming, finishing and final inspection.
Which Applications Commonly Use DSAW Pipe?
DSAW pipe is commonly considered where projects require large diameters, substantial wall thicknesses or closely inspected welded seams. The correct manufacturing route still depends on pressure, temperature, structural loading, corrosion exposure and local requirements.
| Application | Common Seam Route | Why It May Be Considered | Specifications to Confirm |
| Oil and gas transmission | SAWL or SAWH where permitted | Availability in large diameters and specified line-pipe grades | Line-pipe standard, grade, service conditions, toughness and NDE |
| Bulk water pipelines and penstocks | SAWL or SAWH, subject to the project specification | Large-bore welded construction for water conveyance | Design pressure, lining, coating, joints and hydrostatic testing |
| Large-bore industrial firewater or utility mains | SAWL or SAWH only where specifically accepted | May suit specified large-bore main sections | Hydraulic design, local requirements, coating and connections |
| Piling and marine structures | SAWL or SAWH, subject to the structural specification | Availability in large diameters and project-specific lengths | Structural standard, grade, dimensions, loads and corrosion allowance |
| Large-bore industrial piping | SAWL or SAWH where permitted | Covered by certain pressure-tube specifications | Piping code, grade, design conditions, NDE and end preparation |
BAOLAI’s EN 10219 SSAW/HSAW structural spiral pipe provides an example of the helical production route. Suitability remains subject to the complete project specification and engineering review.
If you are sourcing submerged arc welded pipe, contact BAOLAI with the applicable standard and edition, grade, seam route, outside diameter, wall thickness, length, ends, surface treatment, quantity and testing requirements. These details allow BAOLAI to review production feasibility, inspection scope and document requirements before preparing a quotation.
Frequently Asked Questions
Does “Double” Mean Two Separate Weld Seams?
No. “Double” refers to welding each seam from both sides, not to the number of seams. Under API 5L and ISO 3183 terminology, SAWL pipe has one or two longitudinal seams, while SAWH pipe has one continuous helical seam.
Is DSAW Pipe Always Manufactured From Steel Plate?
No. Longitudinal SAWL pipe is commonly formed from plate, while SAWH pipe may be formed from coil or strip. Buyers should specify whether a longitudinal or helical manufacturing route is required.
Can DSAW Pipe Be Produced in Custom Dimensions?
Custom diameters, wall thicknesses and lengths may be available within the mill’s forming, welding and testing limits. Availability also depends on raw material, tooling, transport restrictions and the applicable standard.
What Specifications Should Buyers Confirm Before Ordering DSAW Pipe?
Buyers should state the standard and edition, manufacturing route, seam direction, grade, outside diameter, wall thickness, length and end preparation. The order should also define coating or lining, tolerances, NDT coverage, hydrostatic and mechanical tests, marking and inspection documents.
