Spiral Submerged Arc Welded (SSAW) pipe is easily recognized by the helical weld seam that wraps around the pipe like a paper towel roll. By spiraling the steel strip, mills can produce very large diameter pipe from standard narrow coils, significantly reducing production costs.
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The Manufacturing Advantage
The primary advantage of the spiral process is flexibility. In the DSAW process, if you want a 48" pipe, you need a steel plate that is over 12 feet wide. In the Spiral process, you can make that same 48" pipe using a standard 5-foot wide coil simply by changing the angle of the spiral.
Why is it ideal for Piling? The spiral seam acts as a "stiffener" along the length of the pipe. This gives SSAW pipe excellent resistance to buckling during driving, making it the preferred choice for foundation piles (ASTM A252).
Spiral Weld vs. Straight Seam (DSAW)
While Spiral Weld is king in the piling world, it has limitations compared to straight seam pipe.
| Feature | Spiral Weld (SSAW) | Straight Seam (DSAW) |
|---|---|---|
| Cost | Lower ($) | Higher ($$) |
| Production Speed | Slower (Continuous forming) | Faster (U-O-E Press) |
| Diameter Flexibility | High (Adjustable angles) | Fixed (Limited by plate width) |
| Typical Use | Piling, Dredging, Water | High Pressure Gas, Structural Columns |
Spiral Pipe FAQ
Common questions regarding the quality and applications of SSAW pipe.
Yes. Because the seam wraps helically around the pipe, the total length of the weld is typically 20% to 35% longer than a longitudinal seam on the same length of pipe. This increases the probability of a defect, which is why SSAW is less common in critical high-pressure gas transmission.
Absolutely. It is the industry standard for ASTM A252 Grade 3 piling. However, it is critical that the "skelp end welds" (where one roll of coil ends and the next begins) are located at least 1 foot away from the ends of the pipe to prevent splitting during driving impact.
Spiral mills can produce massive diameters. While standard production goes up to 120 inches (10 feet) OD, specialized mobile mills can produce pipe up to 160 inches for specific bridge caissons or penstock projects.
Common Applications
- Bridge Foundations: Driven open-ended or closed-ended pipe piles.
- Port Infrastructure: King piles, combi-walls, and dolphins.
- Road Boring: Steel casing for underground utility tunnels.
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Manufacturing Methods
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