Welded Steel Pipe: ERW, LSAW & SSAW — Types, Specs & Selection Guide

Welded steel pipe accounts for the majority of the world's pipeline infrastructure — from small-diameter gas distribution mains to 48-inch cross-country transmission corridors. Three distinct manufacturing processes produce three distinct pipe types, each with its own diameter range, pressure capability, cost profile, and appropriate application: ERW (Electric Resistance Welded), LSAW (Longitudinal Submerged Arc Welded), and SSAW (Spiral Submerged Arc Welded). Choosing the wrong type for a project doesn't just affect cost — it can affect code compliance, inspection requirements, and long-term integrity.

ZC Steel Pipe manufactures and exports all three types of welded line pipe to API 5L PSL1 and PSL2, in grades from X52 through X80, with FBE, 3LPE, and 3LPP coating options. We supply pipeline projects across Africa, the Middle East, and South America. This guide explains how each type is made, what it is suited for, and how to select between them for your project.

1. The Three Types of Welded Steel Pipe

All welded steel pipe starts from flat steel — either coil/strip or heavy plate — which is formed into a cylinder and welded along the seam. The three manufacturing processes differ in how the steel is formed, how the weld seam is oriented, and what diameter and wall thickness range they can produce.

2. ERW Pipe — Process, Specs & Applications

2.1 Manufacturing Process

ERW pipe is produced on a continuous forming mill. Hot-rolled strip steel is uncoiled and progressively formed through a series of roll stands into a circular cross-section. The two edges of the strip are brought together and welded using high-frequency electrical resistance — no filler metal is used. The electrical current creates intense localised heat at the seam interface, and the edges are forged together under mechanical pressure to form the weld.

The weld zone is then heat-treated (normalised or full-body heat treated for higher grades) to restore toughness in the heat-affected zone. For PSL2 and higher grades, the weld seam area is 100% inspected by ultrasonic testing before the pipe leaves the mill.

2.2 Key Specifications

2.3 Applications

• Oil and gas gathering lines (2"–12" most common)

• Gas distribution mains and laterals

• Water supply and irrigation pipelines

• ERW casing and tubing for oil wells (API 5CT)

• Structural and mechanical tubing

• Short-run transmission lines at moderate pressure

3. LSAW Pipe — Process, Specs & Applications

3.1 Manufacturing Process

LSAW pipe is produced from heavy steel plate — not coil — using one of two forming processes: UOE (U-ing, O-ing, Expansion) or JCOE (J-ing, C-ing, O-ing, Expansion). In both processes, a single plate is progressively formed into a pipe shape and welded along the longitudinal seam using submerged arc welding (SAW) — first on the inside, then on the outside. The pipe is then mechanically expanded to achieve precise dimensional tolerances.

The use of heavy plate as starting material allows LSAW to achieve much greater wall thicknesses than ERW or SSAW. The double-pass SAW process (inside + outside) produces a fully penetrated, high-quality weld that is 100% inspected by UT and radiography.

3.2 Key Specifications

3.3 Applications

• High-pressure onshore gas transmission pipelines

• Crude oil and product transmission lines (large diameter)

• Offshore flowlines and export pipelines

• Subsea pipelines (with appropriate coating)

• High-yield grade (X70, X80) long-distance pipelines

• Sour service pipelines (PSL2 + Annex H)

Deep dive: LSAW vs Seamless for Large Diameter High-Yield Projects → | LSAW for Offshore and Marine Environments → | LSAW JCOE vs Spiral Pipe for Subsea Risers →

4. SSAW Pipe — Process, Specs & Applications

4.1 Manufacturing Process

SSAW pipe is produced by spirally forming hot-rolled strip steel at a controlled helix angle and welding the resulting helical seam using submerged arc welding — again, inside and outside passes. Because the pipe diameter is determined by the helix angle rather than the strip width, a single strip width can produce a range of pipe diameters by adjusting the forming angle. This flexibility makes SSAW the most economical route to very large diameters.

The spiral seam is longer than a longitudinal seam for the same pipe length, which means more weld length per pipe — and more NDE required per pipe on PSL2 orders. The helical geometry also means that hoop stress in the pipe wall is not perpendicular to the weld seam, which affects fatigue behaviour compared to longitudinal seam pipe.

4.2 Key Specifications

4.3 Applications

• Water transmission mains (large diameter)

• Low to moderate pressure gas distribution

• Large diameter onshore oil pipelines

• Slurry pipelines

• Infrastructure and piling (structural use)

• Irrigation and drainage systems

5. ERW vs LSAW vs SSAW — Full Comparison

6. Welded vs Seamless Pipe

The choice between welded and seamless is one of the most common questions in line pipe procurement. For most pipeline applications above 4" OD, welded pipe is the default — not because seamless is unavailable, but because welded pipe is more economical, more available in large diameters, and fully code-compliant for the application.

Related: Seamless vs Welded Line Pipe: How to Choose → | Seamless vs ERW: When Is the Premium Justified? → | Seamless vs LSAW for High-Pressure Gas Transmission →

7. API 5L Grades for Welded Line Pipe

All three welded pipe types are produced to API 5L / ISO 3183 in multiple grades. Grade selection is driven by the required operating pressure, wall thickness economics, and service environment — not by pipe type. The table below shows which grades are available in each welded form.

Grade guides: API 5L X52 Line Pipe → | API 5L X60 Line Pipe → | API 5L X65 Line Pipe → | API 5L X70 Line Pipe → | API 5L X80 Line Pipe →

8. Coating Options for Welded Line Pipe

Most welded line pipe for buried or subsea service is externally coated to prevent corrosion. The three main coating systems are FBE, 3LPE, and 3LPP — each suited to different temperature ranges and service environments.

Full coating guide: 3LPE vs FBE vs 3LPP Pipe Coating: How to Choose → | 3LPE Coating Standard DIN 30670 →

9. How to Choose: Selection by Application

10. Frequently Asked Questions