Longitudinal Welded Steel Pipe

Longitudinal Welded Steel Pipes refer to welded pipes where the weld seam is parallel to the longitudinal direction of the steel pipe. They are made by rolling steel strips or plates and then welding them longitudinally, characterized by a single straight weld seam.

High-frequency resistance welded straight seam pipes (ERW/HFW) are one of our core products. Using hot-rolled coils as raw materials, they utilize high-frequency current to fuse the pipe joints, achieving a production speed of 20–50 meters per minute. This process creates a small heat-affected zone, resulting in pipes with regular roundness and uniform wall thickness, making it the mainstream production process for small and medium-diameter pipes.

Specifications

Product Performance Advantages

1. High Dimensional Accuracy: The pipe body is regularly formed, with uniform wall thickness and good roundness, facilitating easy on-site installation.

2. Low Defect Rate: The single short weld design significantly reduces internal defects, resulting in a high pass rate for non-destructive testing.

3. Stable Mechanical Properties: Bending resistance, pressure resistance, and seismic resistance all meet industry standards, ensuring safe and reliable use.

4. Excellent Cost-Effectiveness: Lower cost than seamless steel pipes, with high mass production efficiency and shorter delivery cycles.

5. Strong Corrosion Resistance: Can be treated with hot-dip galvanizing, 3PE anti-corrosion, and epoxy powder anti-corrosion, providing excellent rust prevention and acid/alkali resistance.

Surface Treatment Types

1. Original Hot-Rolled Surface: Retains the original hot-rolled surface of the pipe, suitable for indoor steel structures and general water supply applications.

2. Hot-dip galvanizing treatment: Excellent rust and corrosion resistance, making it a specialized pipe material for fire protection and drainage, and agricultural greenhouse frames.

3. Anti-corrosion coating treatment: Utilizes a three-layer polyethylene (3PE) anti-corrosion process, widely used for buried oil and gas transportation and municipal underground pipeline networks.

Application Scenarios

1. Municipal Engineering: Water supply, gas pipelines, sewage discharge, underground integrated pipeline networks.

2. Building Steel Structures: Factory frames, building columns, bridge supports, pile foundation casings.

3. Oil and Gas Energy Sector: Oilfield gathering and transmission pipelines, power plant circulating water pipelines.

4. Industrial Manufacturing: Equipment supporting pipelines, machinery supports, ventilation ducts, cable conduits.

5. Landscaping and Infrastructure Construction: Guardrail posts, greenhouse pipes, road guardrails.

Real-world Application Case Study

Southeast Asia Wind Power and Port Project (2025)

Our company supplied a total of 12,000 tons of 3PE anti-corrosion longitudinal welded steel pipes for a large-scale wind farm and port expansion project in the Philippines. The pipes ranged in outer diameter from 219 to 630 mm and wall thickness from 6 to 12 mm, primarily for wind power foundation piles, seawater cooling pipelines, and gas transmission pipelines.

The project adhered to ISO 3183 and API 5L international standards throughout. All pipes underwent 100% hydrostatic testing, ultrasonic flaw detection of welds, and anti-corrosion layer thickness testing before leaving the factory. The project was completed on schedule and smoothly without any quality issues. The client has reached a long-term cooperation agreement with us. This case fully demonstrates Zhongtian's comprehensive strength in undertaking large-scale overseas infrastructure projects.

Product Comparison Advantages:

1. Compared to seamless steel pipes: Lower cost, faster mass production speed, and can meet the requirements of most normal and medium pressure operating conditions.

2. Compared to spiral welded pipes: Shorter weld seams, smaller deformation, stronger stability in small and medium diameter pipe applications, and better adaptability for on-site construction.

Quality Inspection Items

All Longitudinal Welded Steel Pipes from our factory undergo a full set of rigorous tests before leaving the factory. The process is as follows:

1. Appearance and Dimension Inspection

2. Hydrostatic Test

3. Ultrasonic Testing of Weld Seams

4. Tensile and Impact Tests

5. Anti-corrosion Coating Thickness Inspection

Products comply with domestic and international standards such as GB/T 3091, GB/T 9711, API 5L, and ISO 3183.

FAQ

Q1: What is the maximum pressure capacity of our factory's Longitudinal Welded Steel Pipes?

A The pressure capacity of the pipe is determined by its outer diameter, wall thickness, and material. Standard Q235B high-frequency welded pipes with a wall thickness of at least 3 mm can withstand a maximum pressure of 2.5 MPa in ordinary water and gas transmission applications. Higher-grade pipes such as L245 and X42 can meet the high-pressure requirements of oil and gas transmission.

Q2: What is the approximate delivery time for export orders?

A: Standard 6-meter and 12-meter pipes are in stock, with a delivery time of 7–10 days. Custom lengths, hot-dip galvanized pipes, or 3PE anti-corrosion pipes have a delivery time of 15–25 days. Currently, our products are stably exported to ports and infrastructure projects in Southeast Asia, Singapore, the Philippines, and Myanmar.

Q3: Can you provide third-party testing reports?

A: Yes. We support on-site testing by authoritative institutions such as SGS, BV, and TUV. Each batch of products comes with an original manufacturer's material report, including complete data on chemical composition, mechanical properties, and non-destructive testing, fully complying with international export standards.

In conclusion, as a professional pipe manufacturer and supplier in China, Zhongtian relies on its own factory's advanced high-frequency welding technology and stringent quality control standards to create reliable Longitudinal Welded Steel Pipes. Whether for municipal water supply, oil and gas transportation, wind power, or port infrastructure projects, we can provide cost-effective solutions. Choosing Zhongtian means choosing durable, high-quality straight seam welded pipes.