Differences Between SSAW and LSAW Steel Pipes for Marine Projects

You are designing a marine foundation or a offshore structure. The engineer specifies steel pipe piles. You see terms like SSAW¹ and LSAW² on the drawings. What is the difference, and which one should you choose for a marine environment?

SSAW¹ (Spiral Submerged Arc Welded) and LSAW² (Longitudinal Submerged Arc Welded) pipes differ in their manufacturing process and weld seam orientation. For marine projects, LSAW² pipes are generally preferred for critical applications because they have better fatigue resistance, thicker wall capabilities, and more reliable weld performance under dynamic loads.

I have supplied steel pipes for marine projects across the Middle East and Southeast Asia. A port expansion in the UAE used LSAW² pipes for the main berth piles. A offshore platform in Southeast Asia used SSAW¹ pipes for secondary structures. Let me walk you through the differences and help you choose the right pipe for your marine project.

Difference between LSAW¹ and HSAW² pipes

LSAW¹ and HSAW² are both types of welded steel pipes. The main difference is the orientation of the weld seam.

LSAW¹ (Longitudinal Submerged Arc Welded) pipes have a straight weld seam running parallel to the pipe axis. HSAW² (Helical Submerged Arc Welded) pipes, also called SSAW, have a spiral weld seam that wraps around the pipe at an angle. For marine projects, LSAW¹ pipes are preferred for primary structures due to better fatigue resistance³ and thicker wall capabilities.

Manufacturing Process Comparison

Let me explain how each pipe is made and why it matters for marine applications.

LSAW¹ Pipe Manufacturing
LSAW¹ pipes start with steel plates. The plate is cut to the required width and then formed into a cylinder using a UOE, JCOE, or press bending process. The formed cylinder has a single longitudinal seam. This seam is welded from both the inside and outside using submerged arc welding (DSAW). After welding, the pipe is often mechanically expanded to achieve precise dimensions and reduce residual stresses.

Key characteristics for marine use:

Thicker walls possible (up to 50 mm or more)
Shorter weld length (1 × pipe length)
Weld aligned with pipe axis, better for longitudinal loading
Excellent dimensional precision⁴

HSAW²/SSAW Pipe Manufacturing
HSAW² (also called SSAW) pipes start with steel coils. The coil is unwound and fed into a forming machine at a specific angle. As the steel strip moves forward, it spirals into a tube shape. The spiral seam is welded continuously as the pipe forms. Like LSAW¹, welding is done from both inside and outside.

Key characteristics for marine use:

Limited wall thickness (typically up to 25 mm)
Longer weld length (1.5-2 × pipe length)
Weld at an angle to pipe axis
Can be made in very long lengths (up to 64 m)

Comparison Table for Marine Applications

Feature	LSAW¹ Pipe	HSAW²/SSAW Pipe
Weld orientation	Longitudinal (parallel)	Helical (spiral angle)
Wall thickness	Up to 50 mm+	Up to 25 mm typical
Weld length	1 × pipe length	1.5-2 × pipe length
Fatigue resistance	Better	Acceptable
Driving stress resistance	Better	Acceptable
Dimensional precision	Excellent	Good
Cost per ton	Higher (30-50% premium)	Lower
Best marine use	Primary piles, deep water	Secondary piles, moderate conditions

My Experience
For a marine terminal in the UAE, the engineer specified LSAW¹ for the main berth piles. The wall thickness was 30 mm, which SSAW could not produce. The longitudinal weld provided better resistance to the dynamic loads from ship berthing and wave action.

SSAW pipe

SSAW (Spiral Submerged Arc Welded) pipe¹ is a cost-effective option for marine projects where wall thickness requirements are moderate and driving conditions are not severe.

SSAW pipe is manufactured by forming steel coil into a spiral and welding the seam using submerged arc welding. It is available in diameters from 16 inches to over 120 inches, with wall thicknesses up to 25 mm. SSAW pipes are economical and can be produced in very long lengths, reducing the number of field welds.

SSAW Pipe for Marine Applications

Let me explain where SSAW pipes work well in marine environments.

Advantages of SSAW for Marine

Cost effective²: Lower material cost than LSAW for the same diameter and thickness
Long lengths³: Can be produced in continuous lengths up to 64 m, reducing field splices
Large diameters: Available in diameters over 100 inches, useful for large-diameter piles
Good availability: Widely produced in Asia, Europe, and North America

Limitations of SSAW for Marine

Limited wall thickness⁴: Typically limited to 25 mm, which may not provide enough corrosion allowance for long-life marine structures
Weld fatigue: The spiral weld has lower fatigue resistance than a longitudinal weld under cyclic loading
Driving stress: The weld at an angle can be more susceptible to damage during hard driving
Inspection complexity: Spiral welds are more difficult to inspect with automated ultrasonic testing

Typical Marine Applications for SSAW

Secondary piles in port structures (access trestles, dolphins)
Moderate depth piles in soft soils
Temporary works and cofferdams
Piles in non-critical areas

SSAW Pipe Specifications

Property	Range
Diameter	16" to 120"+ (406 mm to 3,048 mm)
Wall thickness	4 mm to 25 mm typical
Length	Up to 64 m continuous
Steel grades	ASTM A252 Grades 2 and 3, API 5L
Standards	ASTM A252, EN 10219, API 5L

My Experience
For a port expansion project, we used SSAW pipes for the access trestle piles. The water depth was moderate (8 meters), and the soil was soft sand. The SSAW pipes drove easily and cost 25% less than LSAW. For the main berth piles, we used LSAW.

LSAW pipe

LSAW (Longitudinal Submerged Arc Welded) pipe is the preferred choice for critical marine applications where reliability, fatigue resistance¹, and thick walls are required.

LSAW pipe is manufactured from steel plates formed into a cylinder with a single longitudinal weld. The weld is made from both sides (DSAW) for full penetration. LSAW pipes are available in diameters from 16 inches to 60 inches, with wall thicknesses up to 50 mm or more. They are the standard for offshore platforms, deepwater ports, and heavy-duty piling.

LSAW Pipe for Marine Applications

Let me explain why LSAW is the gold standard for marine piles.

Advantages of LSAW for Marine

Thick walls: Can be manufactured with wall thicknesses up to 50 mm or more, providing corrosion allowance² for 50+ year service life
Superior fatigue resistance¹: Longitudinal weld performs better under cyclic loading from waves and ship impacts
Better driving performance: Weld aligned with driving stress direction, reducing risk of failure
Excellent dimensional precision³: Mechanically expanded pipes have tight tolerances
Easier inspection: Straight welds are easier to inspect with automated ultrasonic testing
Higher strength grades: Available in high-strength steels⁴ up to X80 and beyond

Limitations of LSAW for Marine

Higher cost: Typically 30-50% more expensive than SSAW for the same diameter and thickness
Length limitations: Standard lengths are 12-18 meters; longer lengths require special ordering
Diameter limitations: Typically limited to 60 inches; larger diameters are possible but require wider plates

Typical Marine Applications for LSAW

Main piles for deepwater ports and terminals
Offshore platform jacket piles
Bridge foundations in marine environments
Piles for heavy crane loads
Piles requiring high corrosion allowance²

LSAW Pipe Specifications

Property	Range
Diameter	16" to 60" (406 mm to 1,524 mm)
Wall thickness	6 mm to 50 mm+
Length	12-18 m typical, up to 40 m available
Steel grades	ASTM A252 Grade 3, ASTM A572, API 5L X42-X80
Standards	ASTM A252, API 5L, DNV-OS-F101

My Experience
For a deepwater port project, we supplied LSAW pipes with 30 mm wall thickness and 24-inch diameter. The piles were driven to 40 meters depth through dense sand. The longitudinal welds held up perfectly under the hard driving conditions. The client required LSAW because of the 50-year design life and the high wave loads at the site.

LSAW Pipe manufacturing process

The LSAW manufacturing process is critical to the pipe’s quality and performance in marine applications.

LSAW pipes¹ are manufactured through a multi-step process: plate preparation, forming (UOE or JCOE), welding (DSAW), expansion, and inspection. The UOE process² (U-ing, O-ing, Expanding) is the most common for large-diameter pipes. The double submerged arc welding (DSAW) ensures full penetration welds with high integrity.

Step-by-Step Manufacturing Process

Let me walk you through the LSAW manufacturing process.

Step 1: Plate Preparation
Steel plates are inspected for surface defects and dimensions. The edges are beveled to prepare for welding. The plates are cut to the exact width required for the pipe diameter.

Step 2: Forming (UOE Process)
The UOE process² has three stages:

U-ing: The plate is pressed into a U shape using a U-press
O-ing: The U shape is pressed into an O shape using an O-press
Expanding: The pipe is mechanically expanded to achieve precise diameter and reduce residual stresses

Alternative forming methods include JCOE (J-ing, C-ing, O-ing, Expanding) for thicker walls and press bending for smaller diameters.

Step 3: Welding (DSAW)
Double Submerged Arc Welding³ is used:

Inside weld: First pass from inside the pipe
Outside weld: Second pass from outside
The weld is fully penetrated through the wall thickness
Submerged arc process uses granular flux to protect the weld

Step 4: Inspection
The weld is inspected using:

Visual inspection of weld profile
Ultrasonic testing⁴ (UT) for internal defects
Radiographic testing (RT) for critical applications
Mechanical testing of weld coupons

Step 5: Finishing

Pipe ends are beveled for field welding
Hydrostatic testing for pressure applications (if required)
Coating application (if specified)
Marking and documentation

Why This Matters for Marine Projects

The mechanical expansion step ensures precise dimensions, which helps with pile driving
DSAW ensures full penetration welds that can withstand driving stresses
Ultrasonic inspection detects any weld defects before the pipe leaves the mill

My Experience
For a marine project in the Middle East, we visited the mill to witness the LSAW manufacturing process. The UOE forming produced pipes with perfect roundness. The DSAW welds passed ultrasonic inspection with no defects. The client was confident in the product quality.

Conclusion

For marine projects, LSAW pipes¹ are preferred for critical applications due to thicker walls, better fatigue resistance, and reliable weld performance. SSAW pipes² are cost-effective for secondary structures and moderate conditions. Choose based on wall thickness requirements and driving conditions.

Explore this link to understand why LSAW pipes are crucial for marine applications, focusing on their durability and performance. ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩
Discover the cost-effectiveness and suitability of SSAW pipes for various conditions, making them a smart choice for secondary structures. ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩ ↩
Learn about DSAW’s advantages in pipe manufacturing and how it ensures weld integrity. ↩ ↩ ↩ ↩
Discover the importance of ultrasonic testing in ensuring the quality and safety of welded pipes. ↩ ↩ ↩ ↩

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Differences Between SSAW and LSAW Steel Pipes for Marine Projects