ERW Pipe Specifications

Specifications for ERW (Electric Resistance Welded) steel pipe define key characteristics such as outside diameter, wall thickness, pipe length, nominal pipe size, weight, steel grade, dimensional tolerances, and testing requirements. In practice, the required ERW pipe specifications are typically defined by a combination of parameters, including pipe size, wall thickness (or wall thickness class/Schedule), steel grade, length, and applicable product standards. For example, an order might specify ERW pipe conforming to ASTM A53 Grade B, NPS 6, Schedule 40, while also detailing length and testing requirements.

Understanding these specifications is crucial when selecting ERW steel pipe for applications such as water transport, oil and gas pipelines, fire protection systems, structural engineering, and general industrial use.

What are the specifications for ERW steel pipes?

ERW steel pipe specifications refer to the technical parameters that define the requirements for physical properties, dimensions, materials, and performance.

Simply labeling a pipe as "ERW" is insufficient; a complete specification typically includes the following parameters:

Nominal Pipe Size (NPS)
Outside Diameter (OD)
Wall thickness
Wall thickness class (Schedule) or specified wall thickness
Pipe length
Steel grade
Weight
Dimensional tolerances
Pipe end type
Welding and heat treatment requirements
Testing and inspection requirements
Surface condition and coating (if required)

These parameters determine whether the pipe can be installed correctly and whether it is suitable for the intended operating conditions.

1. ERW Steel Pipe Size Specifications

Pipe size is one of the most important specification parameters for ERW steel pipes. ERW pipes are typically designated using the Nominal Pipe Size (NPS) system (based on ASME/US standards), whereas in other standards or markets, they are often designated by their outside diameter in millimeters (mm). For example, NPS 2 corresponds to an outside diameter of 60.3 mm. It is important to note that NPS is merely a nominal designation and does not always equate to the actual outside diameter.

2. ERW Steel Pipe Outside Diameter Specifications

Outside Diameter (OD) refers to the actual external diameter of the steel pipe. For a given nominal size, the outside diameter is usually determined by the applicable dimensional standard, while the wall thickness may vary.

For instance, an NPS 6 pipe has an outside diameter of approximately 168.3 mm, but its wall thickness will vary depending on the selected Schedule or the specifically required thickness.

3. ERW Steel Pipe Wall Thickness Specifications

Wall thickness is another fundamental specification for ERW steel pipes; it influences the pipe's inside diameter, weight, mechanical strength, pressure resistance, corrosion allowance, and service life.

Wall thickness can be specified directly in millimeters (mm) or indirectly through a wall thickness class (Schedule, such as Schedule 10, Schedule 40, Schedule 80, or Schedule 80S). For example, common ERW pipe sizes may be supplied with different wall thicknesses:

NPS	OD	Example Sch 10 thickness	Example Sch 40 thickness	Example Sch 80 thickness
2"	60.3 mm	2.77 mm	3.91 mm	5.54 mm
3"	88.9 mm	3.05 mm	5.49 mm	7.62 mm
4"	114.3 mm	3.05 mm	6.02 mm	8.56 mm
6"	168.3 mm	3.40 mm	7.11 mm	10.97 mm
8"	219.1 mm	3.76 mm	8.18 mm	12.70 mm
10"	273.1 mm	4.19 mm	9.27 mm	15.09 mm
12"	323.9 mm	4.57 mm	10.31 mm	17.48 mm

4. ERW Steel Pipe Length Specifications

Steel pipe lengths are typically specified as standard/random lengths or fixed (cut) lengths.

Common specifications include:

6 meters
12 meters
Single Random Length (SRL)
Double Random Length (DRL)
Fixed length

For example, a buyer might specify:

NPS 6 × Schedule 40 × ASTM A53 Grade B × 6 meters

Fixed-length pipes are usually preferred when a project has specific requirements regarding installation or fabrication dimensions, whereas random-length pipes offer greater flexibility for general supply purposes.

5. ERW Steel Pipe Weight Specifications

The weight of ERW steel pipe is typically expressed in kg/m (kilograms per meter) or lb/ft (pounds per foot).

Weight depends primarily on the following pipe parameters: outside diameter, wall thickness, and length.

For pipes of the same nominal size, a greater wall thickness results in a heavier weight per unit length (per meter).

For example, an NPS 6 Schedule 80 pipe is heavier than an NPS 6 Schedule 40 pipe because the former has a thicker wall.

Pipe weight is particularly important for calculating material quantities, transportation, handling and lifting, and project cost estimation.

6. ERW Steel Pipe End Specifications

The pipe end configuration should be selected based on the connection and installation method.

The most common types include:

Plain ends: Plain-end ERW pipes are typically used for welding or in applications requiring subsequent end processing.

Beveled ends: Beveled ends are commonly used for butt welding. The bevel design facilitates the construction of welded joints.

Threaded ends: Threaded ends are used when the pipe needs to be connected via threaded fittings or other threaded components.

In piping engineering and industrial applications, plain ends and beveled ends are generally more common than threaded ends.

7. ERW Steel Pipe Inspection Specifications

Inspection requirements are typically determined by applicable product standards and project specifications. Key inspection items for ERW steel pipes may include:

Hydrostatic testing – Checks the pipe's resistance to leakage under a specified test pressure.
Non-destructive testing (NDT) – Commonly used to inspect weld seams or detect internal defects (discontinuities).
Mechanical testing – Verifies performance indicators such as tensile strength and yield strength, when required.

FAQs about ERW steel pipe specifications

1. What are the main specifications for ERW steel pipes?

Key specifications for ERW steel pipes include pipe size, outside diameter (OD), wall thickness, pipe schedule, steel grade, length, weight, and end type. Depending on specific application requirements, specifications may also include relevant testing requirements.

2. What sizes are available for ERW steel pipes?

ERW steel pipes come in a wide range of sizes. Common NPS (Nominal Pipe Size) sizes include 1/2, 1, 2, 3, 4, 6, 8, 10, and 12 inches; larger sizes may also be available depending on the manufacturer and product specifications.

3. What is the wall thickness of ERW steel pipes?

The wall thickness of ERW steel pipes depends on the pipe size and the specified schedule or wall thickness value. Common schedule ratings include Schedule 10, Schedule 40, and Schedule 80.

4. What is the difference between NPS and OD?

NPS stands for Nominal Pipe Size, while OD refers to the actual Outside Diameter of the pipe. For example, an NPS 6 pipe has an actual outside diameter of 168.3 mm.

Conclusion

Specifications for ERW (Electric Resistance Welded) steel pipes are primarily determined by parameters such as size, outside diameter, wall thickness, steel grade, length, weight, and end type. These parameters collectively define the specific ERW steel pipe specifications required for a project.

Read more: Applications of ERW Steel Pipe or ERW Pipe Manufacturing Process: From Steel Coil to Finished Pipe