ERW Pipe vs. SSAW Pipe

In steel pipe procurement and engineering applications, ERW pipes and SSAW pipes are two of the most common pipeline types. Whether for oil and gas transportation, urban water supply networks, or building structural support, choosing the right pipe type directly impacts project costs, construction efficiency, and long-term operational safety. Below, we clarify the differences between the two from four dimensions most important to buyers: performance, specifications, cost, and application scenarios.

1. Differences in Manufacturing Process and Weld Quality

ERW pipes utilize high-frequency resistance welding. Simply put, hot-rolled coils are continuously rolled into a cylindrical shape, and then the skin effect and proximity effect of high-frequency current are used to rapidly heat the edges of the steel strip to a molten state, followed by welding under the pressure of extrusion rollers. This process does not use welding wire or flux, the weld composition is essentially the same as the base material, the heat-affected zone is narrow, and the welding speed is fast.

SSAW pipes utilize spiral submerged arc welding. The steel strip is continuously rolled into shape at a certain spiral angle, and then submerged arc welding (using welding wire and flux) is applied to both the inner and outer sides. Its weld seam is helical, with a weld seam length approximately 1.1 to 1.4 times the pipe length.

Several key performance differences:

● Dimensional accuracy: ERW pipes have stricter tolerance control for outer diameter and wall thickness, resulting in better straightness and roundness. SSAW pipes, due to their helical forming, have relatively poorer roundness control.

● Weld strength: The weld seam coefficient for ERW pipes is generally between 0.85 and 1.0, and there may be a certain strength difference between the weld seam and the base material. SSAW pipes are double-sided welded, with weld seam strength essentially equivalent to the base material, and a weld seam coefficient that can reach 1.0.

● Inner surface quality: ERW pipes have a smooth inner wall and a small weld seam allowance, resulting in lower fluid transport resistance. SSAW pipes have a continuous helical weld seam allowance on the inner wall, which can have a certain impact on transport efficiency.

● Pressure resistance: Both can meet the requirements for medium and high pressure transport. However, the weld seam direction of SSAW pipes has an angle with the principal stress direction of the pipe wall, resulting in better stress dispersion.

2. Specifications and Manufacturability

ERW Pipe Size Range: 

Outer diameter generally ranges from 21.3mm to 610mm, with a maximum of around 813mm. Wall thickness typically does not exceed 20mm. Its advantage lies in small to medium diameters of 24 inches (610mm) and below.

SSAW Pipe Size Range: 

Outer diameter starts from 219mm, with a maximum of over 3000mm. Wall thickness can reach 25mm or even thicker. Its advantage is obvious for large diameters.

Therefore, a basic judgment should be made when purchasing: for pipe diameters below 24 inches, ERW pipe is often a more cost-effective choice; for pipe diameters exceeding 24 inches, SSAW pipe is almost the only straight seam or spiral seam welded pipe solution.

3. Procurement Cost and Economic Analysis

Steel pipe cost is one of the core factors in procurement decisions. According to market data from 2024-2025, under the same specifications and steel grades, the ex-factory price of ERW pipe is usually 10%-15% lower than that of SSAW pipe. Taking Φ630×10mm API 5L Gr.B line pipe as an example, ERW pipe costs approximately 5500 RMB/ton, while SSAW pipe costs approximately 6200 RMB/ton.

However, the total life cycle cost (TCO) needs to consider more factors:
a. Transportation costs: ERW pipe is lighter, has higher dimensional accuracy, and is easier to stack and transport.
b. Installation costs: ERW pipe is lightweight and has good straightness, making on-site installation simple and quick; SSAW pipe is heavier, and its ovality may affect the efficiency of circumferential weld alignment.
c. Inspection costs: ERW pipe has only one longitudinal weld, resulting in less non-destructive testing; SSAW pipe has a longer spiral weld, leading to a greater workload for UT/RT testing and a corresponding increase in inspection costs.
d. Maintenance costs: Under normal low- and medium-pressure operating conditions, the difference between the two is not significant; in high-pressure or corrosive media environments, the longer weld of SSAW pipe means more potential monitoring points and maintenance work.

In summary, for small-to-medium diameter, low-to-medium pressure, and cost-sensitive pipeline projects, ERW pipes offer a significant life-cycle cost advantage; for large-diameter water transmission or low-pressure, high-flow projects, SSAW pipes may have a lower overall cost due to their diameter-based economic advantages.

5. Application Scenarios and Selection Recommendations

Based on API 5L, GB/T 9711, and other standards, as well as engineering practice experience, the following selection directions are recommended:

Scenarios where ERW pipes are preferred:

● Low-pressure urban gas pipelines (pressure ≤ 4MPa, diameter ≤ 610mm)
● Municipal water supply pipelines such as tap water and fire protection systems
● Structural applications such as building structures, scaffolding, and pile pipes
● Internal oilfield gathering and transportation pipelines, refined oil transportation
● Precision pipes for automotive and machinery manufacturing
● Any project with strict requirements for dimensional accuracy, internal surface finish, and straightness

Scenarios where SSAW pipes are preferred:

● Large-scale water transmission projects, hydraulic and electrical pressure steel pipes (diameter ≥ 800mm)
● Long-distance low-pressure, high-flow transmission pipelines
● Structural applications such as large-diameter pile pipes, wind turbine towers, and bridge pile foundations
● Oil and gas transmission pipelines operating in Class 3 and 4 (ordinary areas)
● Large-diameter projects that are cost-sensitive and whose pipe diameter exceeds the manufacturing capacity of ERW pipes

Standard limitations: API 5L explicitly stipulates that high-pressure oil and gas pipelines passing through high-altitude and frigid zones, seabeds, and densely populated urban areas (Class 1 and 2 regions) must use LSAW pipe (Straight Seam Submerged Arc Welded Pipe). In these cases, ERW and SSAW are not applicable.

Purchase List: Key Parameters to Confirm During Selection

To ensure accurate selection, it is recommended to clarify the following information when communicating with the supplier:

1) Applicable Standards: API 5L PSL1/PSL2, ASTM A53, GB/T 9711, EN 10225, etc.
2) Steel Grade: Gr.B, X42, X52, X60, X65, X70, etc.
3) Outer Diameter × Wall Thickness and Permissible Tolerances
4) Regional Classification: Is it a Class 1 or 2 high-level region (determining whether SSAW can be used)?
5) Non-Destructive Testing Requirements: Is 100% ultrasonic testing of welds required? Is RT sampling required? 6) Hydrostatic test pressure value
7) Requirement for weld heat treatment (a key quality control step for ERW pipelines)
8) Anti-corrosion coating type and thickness: 3PE, FBE, bare pipe, etc.
9) Pipe end treatment: flat end, bevel, threaded, or grooved

10) Delivery length and weight restrictions

Read more: ERW Pipe vs. Seamless Pipe Cost or ERW Pipe vs. LSAW Pipe