Longitudinal welded pipes are a category of welded steel pipes where the weld seam runs parallel to the pipe's length (longitudinally), as opposed to spiral welded pipes (where the weld follows a helical path). Two of the most common types are LSAW pipe (Longitudinal Submerged Arc Welded) and ERW (Electric Resistance Welded) pipes. While both fall under the longitudinal welded umbrella, they differ significantly in manufacturing, performance, and applications.
Spiral Welded Pipe (SSAW)
Forming Method: Formed by cold extrusion of coiled steel strips, with seams spiraling around the pipe axis at angles of 45°–70° .
Welding Technology: Uses automated double-wire submerged arc welding (DSAW) for internal and external seams simultaneously .
Key Advantages:
One strip width can produce multiple pipe diameters, enhancing material flexibility .
Minimal post-weld straightening due to inherent rigidity from spiral seams .
Longitudinal Welded Pipe (LSAW / ERW)
Forming Method: A steel plate/strip is bent into a cylinder, with the two long edges aligned and welded parallel to the pipe length (longitudinally). LSAW welded pipe uses SAW for thick walls; ERW uses electric resistance welding for thinner walls.
Welding : The longitudinal seam is welded using submerged arc welding-an arc welding process where the weld area is submerged in a granular flux, protecting it from atmospheric contamination. This creates a high-integrity, deep-penetration weld.
LSAW: Submerged arc welding (SAW)
ERW: High-Frequency Resistance Welding
spiral welded pipe vs longitudinal welded pipe
| Feature | Spiral Welded Pipe | Longitudinal Welded Pipe |
| Weld Orientation | Weld runs helically (at an angle to the pipe axis), distributing stress more evenly under external pressure (e.g., from soil in buried pipelines). | Weld runs straight along the pipe length, which may create stress concentration points under bending or external pressure. |
| Diameter Range | Typically 219mm–4064mm , ideal for extra-large diameters. | LSAW: 355.6mm-2320mm; ERW: Generally ≤600mm (24 inches) (smaller diameters). |
| Wall Thickness | Moderate (3.2–40mm); limited by the strip thickness and welding process. | LSAW: Thicker (up to 50mm) for high-pressure applications; ERW: Thinner (≤12mm) for low-to-medium pressure. |
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Applications
- SSAW Steel Pipes
Low-pressure oil/water trunk lines.
Piling and structural foundations (e.g., bridges)
- LSAW Steel Pipe
High-pressure oil and gas transmission pipelines (onshore and offshore).
Industrial pipelines for chemicals, steam, or high-temperature fluids.
Structural uses (e.g., bridge piles, offshore platforms) requiring thick walls and high strength.
- ERW Steel Pipe
Low-to-medium pressure pipelines (water supply, natural gas distribution, irrigation).
Structural uses (scaffolding, automotive parts, furniture frames).
Mechanical tubing (e.g., in machinery, boilers, and heat exchangers) where precise dimensions are critical.
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