Welded pipes are primarily classified into three categories based on manufacturing processes and weld patterns: ERW (resistance-welded pipes), LSAW (flat-seam submerged arc welded pipes), and HSAW/SSAW (spiral submerged arc welded pipes).

Their manufacturing processes and application scenarios each have distinct focuses. In brief: ERW is primarily designed for small and medium diameters, emphasizing efficiency and precision; LSAW excels in large diameters and high-pressure applications, making it the preferred choice for high-risk projects; while HSAW can produce extremely large diameters using narrow materials, offering optimal cost-effectiveness.

Comparison of the Three Main Types of Industrial Welded Pipes

First, I've compiled their key differences into a summary table for quick reference:

Dimension for Comparison	ERW (Electric Resistance Welding)	LSAW (Longitudinal Submerged Arc Welding)	HSAW (Helical Submerged Arc Welding) / SSAW
weld shape	Vertical longitudinal seam, parallel to the tube body	Vertical longitudinal seam, parallel to the tube body	Spiral weld seam, encircling the tube body
raw material	Hot-rolled steel coil	Single-thick plate	Hot-rolled steel coils or narrow strip steel
Applicable Scope	Small to medium (usually ≤ 610 mm)	Medium to large (typically 406 mm – 1500 mm)	Large to extra-large (typically 219 mm – 3660 mm)
Welding Method	High-frequency resistance welding, without welding wire	Double-sided submerged arc welding, using welding wire and flux	Double-sided submerged arc welding, using welding wire and flux
merit	High production efficiency, low cost, and high dimensional accuracy	The weld exhibits excellent performance, high-pressure resistance, and low-temperature corrosion resistance.	Narrow strip material can be used to produce large tubes with minimal equipment investment and low cost.
shortcoming	Only capable of producing thin-walled pipes with small to medium diameters, with potential weld defect risks.	The process is complex and costly.	The weld length is 1.5–2 times the pipe length, with poor control of geometric dimensions.
Typical Application	Urban gas, refined petroleum products, and low-pressure fluid transportation	Long-distance oil and gas pipelines, high-risk areas such as cold regions and seabeds, and offshore engineering projects	Large-diameter water transmission, pile driving, structural pipes, general fluid transportation
Heat Affected Zone (HAZ)	small	small	big
production efficiency	High (~12 meters per minute)	Medium (~4 meters per minute)	Low (~2 meters per minute)

Detailed Analysis of Welded Pipe Types

ERW (Electric Resistance Welding) tube

ERW primarily utilizes the skin effect and proximity effect of electric current to heat the edges of the steel strip to a molten state, followed by applying pressure to achieve fusion. No welding wire is added throughout the entire process.

Core advantages and limitations: ERW pipe welds feature short, smooth seams with excellent dimensional accuracy and low cost. However, the material is sensitive to chemical composition, and there is a risk of incomplete fusion defects in the welds.

Production and Standards: The ERW process employs a high-speed continuous production line, ideal for mass manufacturing. The primary compliance standards include API 5L and GB/T 9711.1.

Application scenarios: It is the absolute mainstream in the field of small and medium-diameter pipes, widely used in urban gas transmission and distribution, refined oil transportation, water supply networks, and structural support for buildings.

LSAW (Longitudinal Submerged Arc Welding) straight seam submerged arc welded pipe

In the LSW process, a single steel plate is first pressed into a cylindrical shape on the forming machine, creating a longitudinal opening. Subsequently, filler welding wire is directly applied to perform double-sided submerged arc welding on both the inner and outer surfaces of the tube blank.

Forming Methods: The mainstream forming processes primarily include UOE, JCOE, and HME. Among these, the UOE method, which incorporates a post-weld diameter expansion process, effectively eliminates internal stresses, resulting in exceptionally high precision of the finished product.

Core Advantage: The weld seam represents the weakest point in the pipe structure. All the advantages of LSAW pipes stem from their precise and controllable welding process, resulting in exceptionally high weld quality.

Standards and Materials: Primarily adhering to standards such as API 5L and GB/T 9711, with stringent requirements for material quality and production processes.

Application scenarios: It serves as the "designated pipeline" for high-risk/high-value applications, such as the main trunk lines of high-pressure oil and gas long-distance pipelines, submarine pipelines, areas with extreme cold or seismic activity, and pipelines crossing rivers.

HSAW (Helical Submerged Arc Welding) pipe

HSAW (also known as SSAW) involves continuously feeding the steel strip into the forming machine at a specific angle, causing it to advance spirally like a coiled spring, with its edges converging to form a helical seam. Subsequently, a double-sided submerged arc welder firmly welds this seam.

Core strengths and weaknesses: The equipment is flexible, but the length of the spiral weld is significantly increased. From a stress analysis perspective, the weld can avoid the primary direction of internal stress; however, its performance is suboptimal under complex stress conditions such as seismic loading.

Classification and Standards: Based on pressure rating, they can be categorized into general fluid transmission pipes (e.g., SY/T5037 standard) and pressure-bearing fluid transmission pipes (e.g., GB/T 9711 standard).

Application scenarios: Widely used in long-distance, large-diameter low-pressure water transmission projects, urban heating pipelines, and pile foundation load-bearing structures for docks and bridges.

Summary: How to choose?

In general, choosing the right welded pipe involves a trade-off between performance, cost, and risk.

Performance first, cost irrelevant: prioritize LSAW.

Optimizing cost-effectiveness: In conventional high-pressure applications such as oil and gas transmission and urban pipeline networks, ERW is an exceptional choice.

Economically achieving ultra-large diameters: For large-diameter projects requiring relatively relaxed pressure and weld quality standards—such as water transmission and pile driving—the HSAW is the optimal choice.