LSAW vs SSAW Pipe: Welded Pipe Types
LSAW (Longitudinal Submerged Arc Welded) and SSAW (Spiral Submerged Arc Welded) are the two primary types of large-diameter welded steel pipe used in pipeline construction. The fundamental difference between LSAW vs SSAW pipe is the weld seam orientation: LSAW has a straight longitudinal seam running parallel to the pipe axis, while SSAW has a helical (spiral) seam that wraps around the pipe at an angle.
Both pipe types are manufactured using the submerged arc welding (SAW) process, which produces deep-penetration, high-quality welds under a blanket of granular flux. The choice between LSAW and SSAW depends on the project requirements for pressure, pipe diameter, wall thickness, and cost.
Manufacturing Comparison
| Feature | LSAW Pipe | SSAW Pipe |
|---|---|---|
| Full name | Longitudinal Submerged Arc Welded | Spiral Submerged Arc Welded |
| Weld orientation | Straight (parallel to axis) | Helical (spiral angle) |
| Raw material | Discrete steel plates | Continuous steel coil/strip |
| Forming method | UOE, JCOE, or press bending | Helical forming from coil |
| Weld passes | ID + OD (double-sided SAW) | ID + OD (double-sided SAW) |
| Size range | NPS 16 to NPS 60+ | NPS 16 to NPS 120+ |
| Wall thickness | Up to 40 mm+ | Up to 25 mm typical |
| Diameter flexibility | Fixed per plate width | Adjustable by changing spiral angle |
| Production speed | Lower (discrete plate) | Higher (continuous coil) |
Performance and Cost
| Parameter | LSAW | SSAW |
|---|---|---|
| Weld joint efficiency | High (E = 1.0 with full RT/UT) | High (E = 1.0 with full RT/UT) |
| Pressure capacity | Higher (straight seam, thicker walls) | Lower (limited by wall thickness) |
| Residual stress | Higher (bending + welding) | Lower (gradual forming) |
| Ovality | Excellent (expansion after welding) | Good |
| Cost per meter | Higher (30-50% premium) | Lower |
| Max. wall thickness | 40 mm+ | ~25 mm |
| Hydrotest | 100% | 100% |
| RT/UT on weld | 100% | 100% |
Specifications
Both LSAW and SSAW pipe are manufactured to the same pipeline specifications:
| Standard | LSAW | SSAW | Scope |
|---|---|---|---|
| API 5L | Yes | Yes | Line pipe for pipelines |
| ASTM A672 | Yes | No | EFW pipe for high-pressure service |
| ASTM A671 | Yes | No | EFW pipe for atmospheric/low-temp |
| EN 10219 | Yes | Yes | Cold-formed structural hollow sections |
| CSA Z245.1 | Yes | Yes | Canadian pipeline standard |
| DNV-ST-F101 | Yes | Yes | Submarine pipelines |
When to Use Each Type
Use LSAW for:
- High-pressure trunk pipelines (API 5L X60 to X80, PSL2)
- Thick-wall applications (above 20 mm)
- Offshore and subsea pipelines per DNV-ST-F101
- Projects requiring UOE expansion for tighter ovality
- Sour service pipelines (NACE MR0175/ISO 15156)
Use SSAW for:
- Low-to-medium pressure pipelines (water, slurry, low-pressure gas)
- Large-diameter applications (NPS 48 and above)
- Piling and structural applications
- Projects where cost optimization is a priority
- Temporary or short-service-life pipelines
For more detail on all welded and seamless pipe manufacturing methods, including ERW, HFW, and EFW, see the complete reference.
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