WHAT IS LSAW PIPE?

LSAW stands for Longitudinal Submerged Arc Welding. It is a highly durable, heavy-wall steel pipe characterized by a single, straight longitudinal weld seam that runs the entire length of the pipe.

The Relationship Between LSAW and DSAW

If you are looking at pipe specifications, you will often see LSAW mentioned alongside DSAW (Double Submerged Arc Welded) pipe. It is important to understand that LSAW is essentially a specific manufacturing method under the umbrella of DSAW.

In an LSAW pipe, the welding is performed on both the inside and the outside of the longitudinal seam (hence the "Double" in DSAW). This double-sided weld guarantees deep penetration, superior weld integrity, and strict adherence to API (American Petroleum Institute) standards.

How is LSAW Pipe Manufactured?

Unlike spiral welded pipes, LSAW is manufactured from individual, heavy steel plates rather than continuous steel coils. The most common and reliable method for producing LSAW pipe is the UOE Process.

• 1. U-Pressing: A heavy steel plate is fed into a massive hydraulic press that bends the edges upward, forming the plate into a "U" shape.
• 2. O-Pressing: The U-shaped plate is moved to an "O" press, which forces the steel into a perfectly cylindrical "O" shape, bringing the two edges together.
• 3. Welding (Inside and Out): The single straight seam is tack-welded, and then fully welded using the Submerged Arc Welding (SAW) process on both the interior and exterior of the pipe.
• 4. Expanding (The "E"): The pipe is mechanically expanded from the inside out. This cold expansion relieves internal manufacturing stresses and ensures perfect dimensional accuracy and roundness.

LSAW vs. HSAW (Spiral Pipe)

The primary alternative to LSAW is HSAW (Helical Submerged Arc Welding), which is also widely known as SSAW (Spiral Submerged Arc Welding).

While both use the submerged arc welding process, LSAW has a single straight seam, whereas HSAW/SSAW features a seam that wraps around the pipe like a spiral staircase. Because LSAW is made from individual steel plates rather than rolled coils, it can achieve much thicker walls and higher pressure ratings than spiral pipe, making it the preferred choice for offshore rigs and high-pressure transmission lines.