About Us
Eastern Steel Manufacturing Co.,Ltd is a leading manufacturer and distributor of seamless steel pipe, welded steel pipe, OCTG products and fittings. We supply first-step processing, semi-finished parts and finished parts to help our clients meet fabrication requirements beyond their capacity or to improve operations by moving forward the pre-production processing.
News
In this column you can find the steel pipe related articles you need, including industry trends, product standards and materials, and some technical guidelines.
Services
Eastern Steel Manufacturing Co.,Ltd not only improve product production and sales services, but also provide additional value-added services. As long as you need, we can complete your specific needs together.
Facility
Eastern Steel Manufacturing Co.,Ltd not only improve product production and sales services, but also provide additional value-added services. As long as you need, we can complete your specific needs together.
Projects
Many years of large-scale project experience in various fields（Oil & Gas, Construction, Power Energy, Marine & Offshore, Water Treatment, Exploration & Drilling Services, Pipeline & Petrochemical etc.）, professional project team is responsible from receiving until the end of the project.
1. What Is Large Diameter Steel Pipe?
Large diameter steel pipe refers to steel pipe with a relatively large outside diameter. The exact size range varies with the product type, manufacturing process, and applicable standard. For general reference, steel pipes with an outside diameter above 108 mm are commonly considered large diameter pipes.
Large diameter steel pipes can be manufactured as either seamless or welded pipes, depending on the required size, specifications, and production process.
Seamless steel pipe is produced from a solid steel billet. The billet is heated, pierced to form a hollow section, and then rolled or sized to the required diameter and wall thickness.
Seamless pipe is commonly specified for pressure piping, process systems, energy equipment, and other applications where seamless construction is required by the design or applicable standard.
Welded steel pipe is made by forming steel plate or coil into a tubular shape and joining the edges by welding. Different welding processes are used for different pipe sizes and production requirements, including ERW, LSAW, and SSAW.
Welded pipe is widely used for large-diameter applications because the manufacturing process can accommodate a broad range of outside diameters and wall thicknesses. Common applications include oil and gas transmission, water pipelines, structural projects, and large-scale infrastructure.
| Aspect | Seamless Steel Pipe | Welded Steel Pipe |
|---|---|---|
| Manufacturing | Produced from a solid billet by piercing and rolling | Formed from steel plate or coil and welded |
| Weld Seam | None | Present |
| Common Types | Hot-finished, cold-drawn | ERW, LSAW, SSAW |
| Size Range | Depends on manufacturing process and applicable standard | Available in a wide range of diameters, including very large sizes |
| Typical Materials | Carbon, alloy, and stainless steel | Carbon, alloy, and stainless steel |
| Common Applications | Pressure piping, process systems, energy equipment | Oil and gas transmission, water pipelines, structural and infrastructure projects |
| Cost | Generally higher | Generally lower for many large-diameter applications |
Large diameter steel pipe sizes are usually specified by outside diameter (OD) and wall thickness (WT). Depending on the applicable standard and project requirements, pipes may also be identified by DN or NPS.
| Specification | Typical Range |
|---|---|
| Outside Diameter (OD) | 108 mm – 1200 mm+ |
| Wall Thickness (WT) | 5 mm – 50 mm |
| Standard Length | 6 m or 12 m |
| Custom Length | Available according to project requirements |
OD × WT gives the actual outside diameter and wall thickness of the pipe. DN (Nominal Diameter) and NPS (Nominal Pipe Size) are nominal designations used for pipe sizing and component matching; they do not directly indicate the actual outside diameter.
Actual wall thickness options depend on the pipe type, material, and applicable standard.
| DN / NPS | Outside Diameter (mm) | Typical Wall Thickness (mm) |
|---|---|---|
| DN200 (8") | 219.1 | 8–20 |
| DN300 (12") | 323.9 | 10–30 |
| DN500 (20") | 508.0 | 12–40 |
| DN800 (32") | 813.0 | 20–50 |
| DN1000 (40") | 1016.0 | 20–50 |
The required wall thickness depends on the design pressure, material grade, temperature, applicable standard, and service conditions.
Carbon steel is widely used in oil and gas transmission, water pipelines, structural projects, and general industrial applications. Common specifications include API 5L for line pipe, ASTM A252 for pipe piles, and ASTM A106 for seamless pipe used in high-temperature service.
Alloy steel is used where higher strength or better performance at elevated temperatures is required. ASTM A691 covers electric-fusion-welded carbon and alloy steel pipe for high-pressure, high-temperature service.
Stainless steel is used where corrosion resistance is required. Common grades include 304/304L and 316/316L, while large diameter welded stainless steel pipe is covered by standards such as ASTM A358 and ASTM A409.
Duplex grades such as 2205 and Super Duplex 2507 are used for chloride-containing and marine environments because of their higher strength and resistance to chloride stress corrosion cracking.
Long-distance oil and gas pipelines use large diameter pipe to transport crude oil, natural gas, and refined products. LSAW and SSAW pipes are widely used for large-diameter transmission lines, with API 5L commonly specified for line pipe.
Water transmission projects use large diameter pipe for municipal water mains, irrigation systems, desalination plants, and water intake and discharge lines. Large internal diameters allow high flow rates over long pipeline distances.
Driven piles, offshore wind turbine monopiles, jacket legs, and bridge foundations are common applications for large diameter structural pipe. ASTM A252 and EN 10219/10210 are among the standards used for structural and piling applications.
Refineries and chemical plants use large diameter pipe for process lines, manifolds, headers, and other fluid-handling systems. Stainless steel, duplex steel, and alloy steel are used where the service involves corrosive media, high temperatures, or demanding operating conditions.
Power plants use large diameter pipe in circulating water systems, cooling water lines, intake and discharge systems, and other high-flow applications. These systems require pipes capable of handling continuous high-volume flow and pressure fluctuations caused by hydraulic surge or water hammer.
The main factors to check when specifying large diameter steel pipe include size, pipe type, material, applicable standard, and inspection requirements.
| Selection Factor | What to Check | Examples |
|---|---|---|
| Pipe Size | Outside diameter, wall thickness, and length | OD × WT; DN or NPS |
| Pipe Type | Manufacturing process, size, and applicable standard | Seamless; ERW; LSAW; SSAW |
| Material & Grade | Steel grade and service conditions | Carbon steel; alloy steel; stainless steel; duplex steel |
| Product Standard | Standard covering the pipe type and application | API 5L; ASTM A252; ASTM A671/A672; ASTM A691; AWWA C200 |
| Standard | Scope / Typical Use |
|---|---|
| API 5L | Line pipe for oil and gas transmission |
| ASTM A106 | Seamless carbon steel pipe for high-temperature service |
| ASTM A252 | Steel pipe piles for foundation applications |
| ASTM A671 / A672 | Electric-fusion-welded carbon steel pipe for specified service conditions |
| ASTM A691 | Electric-fusion-welded carbon and alloy steel pipe for high-pressure, high-temperature service |
| EN 10219 / EN 10210 | Structural hollow sections |
| AWWA C200 | Steel water pipe for water transmission |
| ASTM A358 / A409 | Welded austenitic stainless steel pipe, including large diameter sizes |
Hydrostatic Testing: Verifies the pipe's ability to withstand the specified test pressure.
Ultrasonic Testing (UT): Detects internal and weld-related discontinuities.
Radiographic Testing (RT): Examines weld integrity using X-ray or gamma radiation.
Mechanical Testing: Includes tensile strength, yield strength, and elongation.
Chemical Analysis: Verifies the chemical composition of the specified steel grade.
Visual and Dimensional Inspection: Checks surface condition, outside diameter, wall thickness, length, and other dimensional requirements.
Q1. What is the difference between seamless and welded large diameter steel pipe?
Seamless steel pipe is produced from a solid billet without a weld seam, while welded steel pipe is formed from steel plate or coil and joined by welding.
Q2. What does OD mean in steel pipe?
OD (Outside Diameter) is the external diameter of the pipe. It is commonly specified together with wall thickness (WT) and may be used alongside DN or NPS to define pipe size and ensure compatibility with fittings and piping systems.
Expression of Diameter of Large Diameter Steel Pipe
Steel Number Indication and Specification Table of Large Diameter Steel Pipes
E-mail: sales@eastern-steels.com
