Seamless Pipe vs ERW Pipe
Seamless pipe is extruded from a solid billet — no weld seam, uniform strength all around. ERW pipe is rolled from a flat strip and welded longitudinally with an electric resistance weld. Seamless is stronger and more reliable for high-pressure or critical service; ERW is cheaper and more readily available in larger sizes.
Side-by-side comparison
| Attribute | Seamless Pipe | ERW Pipe |
|---|---|---|
| Manufacturing | Pierced/extruded from billet | Rolled from strip + ERW welded |
| Weld seam | None | Longitudinal weld |
| Pressure rating | Higher (uniform) | Limited by weld strength |
| Wall thickness uniformity | Excellent | Good |
| Surface finish | Rougher (mill scale) | Smoother (cold-formed) |
| Available sizes | Up to ~500 mm OD | Up to ~600 mm+ OD |
| Cost | 20–50% more | Baseline |
| Common uses | Hydraulic, high-pressure, oil & gas, boilers | Plumbing, water lines, structural, low-pressure conveyance |
When to choose Seamless Pipe
Use seamless pipe for high-pressure, high-temperature, or critical-service applications — boilers, hydraulics, oil & gas, refinery, where weld failure is unacceptable.
Buy Seamless Pipe on MetaleMartWhen to choose ERW Pipe
Use ERW pipe for general water lines, plumbing, structural columns, low-pressure gas distribution — anywhere the cost difference matters and pressure is moderate.
Buy ERW Pipe on MetaleMartFrequently asked questions
Can ERW pipe handle the same pressure as seamless?
Generally no — ERW pressure ratings are derated due to the weld seam. For pressures above 100 bar, seamless is usually specified.
How can I identify the type by inspection?
Look for a continuous longitudinal line on the inside or outside of the pipe — that is the ERW weld bead. Seamless has none.
Is seamless always better?
Better quality, but for many applications (water, low-pressure gas, structural), ERW is fully adequate and 30–50% cheaper.