Longitudinal Submerged Arc Welding (LSAW) Processes

Introduction to Steel Pipe Manufacturing

Steel pipes are elongated hollow tubes designed to transport products between locations. They are manufactured through two primary methods: welded pipe production and seamless pipe production. Both processes begin with raw steel being cast into more manageable forms such as slabs, hot billets, or flat strips. The material is then either stretched to create seamless pipes or formed by joining the edges of flat steel strips with welds.

LSAW Pipes: Applications and Advantages

When operational conditions demand high wall thickness due to elevated internal or external pressures, LSAW pipes typically represent the most cost-effective solution. These pipes excel in high-pressure environments and offer excellent low-temperature corrosion resistance. The diameter range for LSAW pipes is more extensive than Electric Resistance Welding (ERW) pipes, typically spanning from 16 inches (406 mm) to 60 inches (1500 mm).

LSAW steel pipes are manufactured from medium to heavy thickness steel plates that undergo cold forming. The material properties of these plates significantly influence the final pipe characteristics. Once formed, the pipes are welded using double submerged arc welding techniques and undergo diameter expansion. LSAW pipes offer a wide specification range and exhibit favorable mechanical properties including good toughness, ductility, uniformity, and compactness.

LSAW Manufacturing Process

The production of longitudinal submerged arc welded pipes involves bending and welding wide steel plates. These plates are typically sourced from leveled hot-rolled coils and are processed through either JCOE or UOE forming methods. In these processes, the steel plate is progressively shaped to resemble the letters "J," "C," "O," or "U" before final expansion.

UOE Manufacturing Method

Figure 1: Diagram showing the Longitudinal Seam Submerged Welded (LSAW) pipe production using the UOE process

The UOE method is a common approach for producing longitudinally welded large-diameter pipes. The process begins with beveling the longitudinal edges of steel plates using carbide milling equipment. These beveled plates are initially formed into a U-shape using a U-press, then further shaped into an O configuration with an O-press.

Quality Control and Testing

LSAW pipes undergo rigorous inspection procedures to ensure quality and reliability. These include:

• Chemical component analysis
• Mechanical properties testing (ultimate tensile strength, yield strength, elongation)
• Technical property evaluations (flattening test, bending test, blow test, impact test)
• Exterior size inspection
• Hydrostatic testing
• X-ray examination

Applications of LSAW Steel Pipes

LSAW pipes serve numerous essential applications across various industries. The primary uses include:

• Oil and natural gas transportation
• Gas distribution networks
• Central heating systems
• Water supply infrastructure
• Sewage treatment facilities
• Low-pressure fluid delivery systems

These applications highlight the versatility and importance of LSAW pipes in critical infrastructure development and maintenance.

Figure 2: Longitudinal seam Submerged Arc Welded LSAW pipes