In large-scale infrastructure, oil and gas transmission pipelines, and municipal water supply projects, selecting the right welded steel pipe is a critical decision that directly impacts project safety and cost control. In international engineering markets, SSAW (Spiral Submerged Arc Welded Pipe) and LSAW (Longitudinal Submerged Arc Welded Pipe) are the two most commonly used large-diameter steel pipes.

Although both are manufactured using submerged arc welding technology, their forming methods are fundamentally different. As a result, they show significant differences in mechanical performance, production cost, and application fields. This guide provides a comprehensive comparison to help you make the most suitable procurement decision.

I. Definition and Core Manufacturing Process

1. SSAW (Spiral Submerged Arc Welded Pipe)

SSAW steel pipes are produced from hot-rolled steel coils, which are continuously formed into a spiral shape at a specific helix angle and welded using double-sided submerged arc welding.

Keywords: continuous production, coil-based raw material, spiral weld seam
Industry terms: spiral steel pipe, spiral welded pipe, HSAW

2. LSAW (Longitudinal Submerged Arc Welded Pipe)

LSAW steel pipes are manufactured from medium and heavy steel plates. The plates are pressed or formed into a cylindrical shape using molds or forming machines and then welded along a longitudinal seam.

Main processes: JCOE (step forming), UOE (press forming and expansion)
Keywords: single pipe production, plate material, straight longitudinal seam

II. Key Technical Comparison Table

Comparison Item	SSAW Spiral Steel Pipe	LSAW Longitudinal Steel Pipe
Weld Seam Type	Spiral seam	Straight longitudinal seam
Raw Material	Hot-rolled steel coil (Coil)	Medium & heavy steel plate (Plate)
Production Efficiency	Very high (continuous production)	Lower (single pipe forming)
Diameter Range	Extremely wide (up to DN3500+)	Typically up to DN1500
Wall Thickness	Medium thickness	Can produce extra-thick wall pipes
Geometric Precision	Good	Very high (after cold expansion)
Pressure Rating	Medium to high pressure	High pressure & ultra-high pressure
Cost Level	Highly cost-effective	Relatively expensive
Standards	API 5L, ASTM A252, GB/T 9711	API 5L, ASTM A671, GB/T 9711

III. Structural Performance and Safety Analysis

SSAW Stress Distribution Advantage

The spiral weld seam distribution allows SSAW pipes to distribute internal pressure more evenly. Since the weld is not parallel to the pipe axis, the main stress acting on the weld is reduced, providing better resistance to crack propagation.

Another key advantage is its ability to produce ultra-large diameter pipes (over 3 meters) using relatively narrow steel coils, making it irreplaceable in large-scale water diversion and transmission projects.

LSAW Quality Stability Advantage

LSAW pipes have only one straight longitudinal weld seam, meaning the total weld length is significantly shorter. This reduces the statistical probability of welding defects.

In addition, LSAW pipes undergo cold expansion (expansion process), resulting in:

Extremely high dimensional accuracy (roundness and straightness)
Uniform residual stress distribution
Excellent performance in high-pressure pipeline systems

Therefore, LSAW is widely preferred for high-pressure oil and gas transmission pipelines.

IV. Cost Difference Analysis: Why LSAW Is More Expensive

In global markets, LSAW pipes are generally more expensive than SSAW pipes. The main reasons include:

1. Raw Material Cost Difference

SSAW uses steel coils, which offer higher material utilization and lower cost.
LSAW uses steel plates, which involve more processing steps and higher material loss.

2. Equipment Investment

LSAW production lines (JCOE or UOE) require massive hydraulic presses and heavy machinery. The capital investment is several times higher than SSAW production lines.

3. Manufacturing Process Logic

SSAW is a continuous production process with high output efficiency.
LSAW is a step-by-step forming process, resulting in slower production cycles and higher labor and processing costs.

V. How to Select the Right Pipe for Your Project

Preferred Applications for SSAW (Spiral Steel Pipe)

Municipal Infrastructure & Water Supply

Suitable for large-diameter, cost-sensitive projects with medium operating pressure, such as freshwater transmission and drainage systems.

Foundation Piling

With excellent length capability (up to 30 meters per single pipe) and large diameters, SSAW is widely used in ports, bridges, and offshore platform foundations.

Low-Pressure Fluid Transport

Includes industrial cooling water, ventilation systems, and dredging projects.

Preferred Applications for LSAW (Longitudinal Steel Pipe)

High-Pressure Oil & Gas Transmission

Used in national energy backbone pipelines such as high-pressure natural gas and crude oil transmission systems.

Severe Operating Conditions

Includes deep-sea pipelines and cold-region pipelines requiring excellent low-temperature toughness and thick wall designs.

High-Grade Steel Projects

When design requirements reach X70 or X80 steel grades, LSAW offers more stable mechanical performance.

VI. Quality Control Recommendations in Export Projects

Regardless of pipe type, the following inspection requirements must be clearly specified in procurement contracts:

1. Full NDT Coverage

100% Ultrasonic Testing (UT)
X-ray Testing (RT) for critical weld sections

2. Hydrostatic Testing

Each pipe must undergo at least a 10-second pressure holding test to ensure zero leakage.

3. Certification Requirements

For export projects, ensure the manufacturer holds:

API 5L certification
ISO 9001 quality management system certification

4. Third-Party Inspection

It is strongly recommended to appoint international inspection agencies such as BV or SGS for:

On-site production monitoring
Pre-shipment inspection