Straight Seam Welded Pipe

Tianjin Brisk Steel is one of the manufacturers of Straight Seam Welded Pipe in China. Our products are mainly exported to the Middle East, Southeast Asia, Europe, New Zealand, and other regions.If you would like to learn more about our products, feel free to contact us and send your purchase list.

 PRODUCT

Tianjin Brisk Steel focus on produce and supply hollow section and steel pipe

Straight seam welded steel pipe is steel pipe manufactured with a single weld seam running the full length of the pipe in a straight line, parallel to the pipe axis - as opposed to spiral (helical) welded pipe, where the seam wraps around the pipe body at an angle. "Straight seam welded" is a manufacturing category rather than a single product: depending on diameter and wall thickness, it is produced by one of two distinct processes:

• ERW (Electric Resistance Welded) straight seam pipe - used for small to medium diameters (typically up to ~660mm), where steel coil is roll-formed into a cylindrical shape and the seam is joined by high-frequency electric resistance welding, without added filler metal.
• LSAW (Longitudinal Submerged Arc Welded) straight seam pipe - used for medium to large diameters, where steel plate is cold-formed (JCOE process) or bent (UOE process) into a cylinder and the seam is welded with submerged arc welding, using filler wire, typically with both an internal and external weld pass.

Both processes produce a straight seam pipe, and both are engineered as an alternative to spiral welded (SSAW) pipe, which is generally more economical for medium-to-large diameters but has a longer total weld seam length per pipe and a helical seam geometry that some structural and pressure applications specify against.

A frequent point of confusion for buyers is choosing between straight seam and spiral seam pipe at overlapping diameters (roughly 406mm–1420mm, where both are commonly available). Key differences that affect selection:

• Seam length and inspection burden: A straight seam pipe has one seam per pipe length; a spiral pipe of the same length has a much longer total seam (due to the helical path), meaning more total weld length to inspect, though modern automated UT largely offsets this in practice.
• Material yield from plate/coil: Spiral pipe can be produced from narrower coil widths at a given diameter, sometimes improving material yield; straight seam LSAW pipe typically requires wider plate matched closely to the finished diameter.
• Roundness and out-of-ovality: Straight seam LSAW pipe, especially after mechanical expansion, often achieves tighter roundness tolerances, which matters for tight-fit applications like piling and flange connections.
• Industry convention by application: Long-distance oil and gas transmission pipelines commonly specify straight seam LSAW pipe per API 5L, while water transmission and general structural piling projects often accept either straight or spiral seam depending on project specification and regional supply availability.

• Simplified, linear inspection path: A single straight weld seam is easier to track and fully inspect with automated ultrasonic testing (UT) systems compared to a continuously rotating helical seam.
• Predictable mechanical properties along the seam: Because the seam does not wrap around the pipe circumference, straight seam pipe generally shows more consistent hoop-direction mechanical properties, which some pressure and structural codes prefer.
• Wide standard support: Straight seam pipe (both ERW and LSAW) is directly referenced across most major international standards - API 5L, ASTM, EN, and ASME - simplifying specification and cross-border procurement.
• Better fit for critical-service pipelines: For sour service, high-pressure, or offshore pipelines, straight seam LSAW pipe with double-sided SAW welding and full-length UT/RT is the more commonly specified construction for maximum weld reliability.

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