LSAW vs. DSAW: A Comprehensive Analysis of the Differences and Applications of These Two Steel Pipe Manufacturing Processes

Welded steel pipe is an indispensable material in oil and gas transportation, infrastructure construction, offshore engineering, and steel structure projects. In the manufacturing process of welded steel pipe, the terms LSAW (Longitudinal Submerged Arc Welding) and DSAW (Double Submerged Arc Welding) are frequently used. While seemingly similar and even interchangeable in some applications, they differ significantly in their definitions, manufacturing processes, process characteristics, and application areas.

This article will provide an in-depth analysis of the definitions, process flows, performance characteristics, and application scenarios of LSAW and DSAW, helping engineers, procurement managers, and technical decision-makers make informed material selection decisions.

I. Basic Definitions and Differences
LSAW stands for Longitudinal Submerged Arc Welded and refers to longitudinally submerged arc welded pipe. This type of pipe is manufactured by rolling steel plate longitudinally into a tubular shape and then welding the inner and outer seams using submerged arc welding, with the welds running parallel to the pipe axis.

DSAW stands for Double Submerged Arc Welded, emphasizing the welding method. Submerged arc welding (SAW) refers to the use of submerged arc welding (SAW) on both the inside and outside of the pipe body, resulting in a double-sided weld. This welding method ensures weld quality and improves weld density and strength.

It should be noted that LSAW refers to a combination of forming and welding methods for steel pipes, while DSAW more closely describes the welding process. In actual production, most LSAW pipes are welded internally and externally using the DSAW process.

II. Manufacturing Process Analysis
LSAW pipes are typically manufactured using the UOE, JCOE, or CFE forming processes. The entire process includes steel plate pretreatment, edge beveling, press forming, spot welding positioning, internal welding, external welding, expansion, and subsequent heat treatment and testing. This longitudinal forming method effectively controls pipe straightness and dimensional accuracy, making it suitable for the production of large-diameter, thick-walled steel pipes.

DSAW emphasizes the double-sided welding technique used during the welding process. Whether it is longitudinally formed LSAW pipe or spirally formed SSAW pipe, as long as both internal and external welds are welded using SAW, it can be called DSAW. Double-sided welding significantly improves weld strength, reduces the probability of weld defects, and enhances safety.

III. Performance Comparison
LSAW pipe, with its longitudinal weld seam, provides more uniform force distribution, making it particularly suitable for high-pressure transmission projects. Its high forming precision and highly controllable welding process make it commonly used in projects requiring high strength and stability, such as long-distance oil and gas pipelines, submarine pipelines, and bridge foundations.

The DSAW process enhances weld strength and tightness through dual internal and external welding, making it particularly suitable for projects requiring high weld strength and zero leakage risk. While it places high demands on welding equipment and process control, the resulting product offers exceptional safety and is commonly used in nuclear power, hydropower, pressure vessels, and ultra-high-pressure transmission systems.

IV. Application Comparison
LSAW steel pipe is widely used in oil and gas pipelines, urban water distribution networks, power station cooling systems, bridge pile foundations, and offshore platform structural supports. Its high precision and strength make it the material of choice for long-distance, high-flow transmission.

DSAW steel pipe is often used in environments requiring a higher safety margin, such as subsea pipelines in deep-sea oil and gas production, LNG cold zone piping, high-pressure boiler piping, nuclear power plant cooling systems, and main transmission lines in petrochemical plants. In these scenarios, the quality of the pipe welds is directly related to the stable operation and service life of the entire system.

V. Technical Summary
Although LSAW and DSAW have some overlap, they essentially represent a forming method and a welding process, respectively. LSAW is currently the mainstream method for manufacturing large-diameter, thick-walled steel pipe, while DSAW is a key process for ensuring weld quality. In practical applications, LSAW pipe is mostly welded using DSAW, so the two are not mutually exclusive but rather complement each other.

For end users, the selection process should be based on a comprehensive consideration of multiple factors, including the operating environment, pressure rating, media characteristics, and structural load-bearing requirements. For applications requiring high pressure, high corrosion, or extreme environments, high-strength steel pipe welded using the DSAW process is recommended. When transporting oil, gas, or water, or used in structural foundations, LSAW steel pipe offers excellent strength, sealing, and cost-effectiveness.

VI. Conclusion
With the global energy transition and the continued advancement of major engineering projects, the quality and performance of welded steel pipe are gaining increasing attention. A thorough understanding of the technical essence of LSAW and DSAW processes will help make scientific, economical, and reliable decisions during procurement, design, and construction. In the future, as manufacturing technology and material processing continue to advance, these two processes will demonstrate their critical value in even more extreme environments.

For more information on welded steel pipe technical specifications, testing standards, quality control processes, or project application examples, please contact a professional steel pipe manufacturer for customized solutions.