Spiral steel pipe

I. What is a spiral welded pipe?

Helical welded pipe, formally known as helically submerged arc-welded pipe, is a type of steel pipe produced by rolling low-carbon carbon structural steel or low-alloy structural steel strips into a pipe blank at a specific helical angle (known as the forming angle), and then welding the pipe seam to complete the pipe.

Its most distinctive external feature is that spiral weld seam.

II. Main Features

The characteristics of spiral welded pipes are very distinct, possessing both significant advantages and certain limitations:

Advantage:

1. Large caliber, flexible material usage:

Using steel strips of the same width, it is possible to produce steel pipes of various diameters by simply changing the forming angle.

The diameter range that can be produced is wide; currently, domestically, it can reach as much as 3.6 meters or even larger—something that straight-seam welded pipes simply cannot match.

2. Low cost and good economic benefits:

The price of raw materials (steel strips) is typically lower than that of steel plates with the same specifications, and the production process features high continuity, resulting in lower overall costs.

3. Reasonable load-bearing capacity:

Since the weld seam is spiral-shaped, it avoids concentrating the weld along a single straight line, thereby ensuring relatively uniform load-bearing capacity of the steel pipe in the direction of the principal stress.

4. High dimensional accuracy:

Using hot-rolled steel strip as the raw material, its wall thickness tolerance is typically smaller and more uniformly distributed than that of steel plates.

Limitations:

1. Weld length:

Compared to straight-seam welded pipes, steel pipes of the same length have weld seams that are 30% to 100% longer. This means that the probability of welding defects is relatively higher.

2. High internal stress:

The forming and welding processes can leave significant residual stresses within the pipe body, which may have a certain impact on the steel pipe's pressure-bearing capacity and dimensional stability.

3. Slow production speed:

Because it uses spiral progressive forming, its production speed is typically lower than that of high-quality straight-seam submerged arc welded pipes.

III. Major Manufacturing Processes

Its production process clearly reflects its characteristics:

Unrolling → Leveling → Edge trimming → Butt welding → Milling edges → Conveying → Pre-bending → Forming → Internal welding → External welding → Cutting off → Finishing → Inspection

Among these, forming and internal and external submerged arc welding are the two core processes.

IV. Major Application Areas

Due to their large diameter and cost advantages, spiral welded pipes are widely used in the following fields:

1. Low-pressure fluid conveyance:

Water conveyance: urban water supply and drainage networks, agricultural irrigation pipes, and large-scale water conservancy projects.

Gas transmission: Used for medium- and low-pressure urban gas pipeline networks.

Oil transportation: Early and some low-pressure oil-and-gas pipelines.

2. Structural support sector (this is a very important market):

Pile pipes: Pile pipes used for foundations in construction, bridges, and docks—this is one of the largest application markets for spiral welded pipes.

Support columns: Used for bridge piers, columns in large-scale factory buildings, and the like.

3. Other fields:

Wind power generation: Section (part) used to manufacture wind turbine tower sections.

Corrugated pipe culvert: A culvert used for roads and railways.

V. In-depth Comparison with Straight Seam Welded Pipes

Helical welded pipe is located in the “low-cost” and “moderate performance” quadrant, making it an ideal choice for cost-sensitive applications with large-diameter requirements.

Longitudinally Submerged Arc Welded (LSAW) pipes are positioned as a high-performance, highly reliable solution, but they also come with a higher price tag.

In addition to their positioning in the chart, they also have the following key differences in technical details: