ERW carbon steel pipe sizes

ERW carbon steel pipe sizes are commonly specified by NPS (Nominal Pipe Size), outside diameter (OD), wall thickness (WT), inside diameter (ID), and pipe Schedule. Common ERW carbon steel pipe sizes range from small NPS sizes such as 1/8" and 1/4" to large diameters, depending on the manufacturing standard and application. Among them, Schedule 40 and Schedule 80 are two of the most commonly referenced wall-thickness options for piping systems.

What Are ERW Carbon Steel Pipe Sizes?

ERW carbon steel pipe sizes describe the dimensional characteristics of an electric resistance welded carbon steel pipe. The most important dimensions are:

NPS: Nominal Pipe Size, normally expressed in inches.
OD: Outside diameter of the pipe.
WT: Nominal wall thickness.
ID: Approximate inside diameter calculated from OD and wall thickness.
Schedule: A designation used to identify the pipe wall-thickness series, such as SCH 40 or SCH 80.
Weight: The theoretical weight of the pipe, usually expressed in kg/m or lb/ft.

Note: NPS does not always equal the actual outside diameter. For example, NPS 2 ERW pipe has an actual OD of 60.3 mm (2.375 in), rather than 2 inches.

ERW Carbon Steel Pipe Size Chart

The following table summarizes common ERW carbon steel pipe dimensions for Schedule 40 and Schedule 80. The dimensions are based on the standard NPS/OD/WT system commonly used for carbon steel piping.

Common ERW Carbon Steel Pipe Sizes – SCH 40 vs SCH 80

ERW Pipe Size: NPS vs OD

One of the most common sources of confusion when purchasing ERW carbon steel pipe is the difference between NPS and actual OD.

NPS is a nominal designation, while OD is the actual standardized outside diameter. For example:

ERW Carbon Steel Pipe Schedule and Wall Thickness

Pipe Schedule is directly related to wall thickness, but Schedule is not a universal fixed wall thickness for every NPS.

For example:

NPS 2 SCH 40 → 3.91 mm wall thickness
NPS 2 SCH 80 → 5.54 mm wall thickness
NPS 6 SCH 40 → 7.11 mm wall thickness
NPS 6 SCH 80 → 10.97 mm wall thickness

The OD remains the same for a given NPS, while increasing the Schedule generally increases the wall thickness and decreases the internal diameter.

How to Choose the Right ERW Carbon Steel Pipe Size

Selecting an ERW pipe size requires more than choosing the nominal diameter. The following factors should be considered:

1. Determine the required flow capacity

The required flow rate influences the required internal diameter. A larger ID generally allows greater flow capacity and lower flow velocity for a given fluid.

2. Select the NPS

Choose the nominal pipe size based on the required flow rate, connection size, equipment interface and piping design.

3. Select the wall thickness

Wall thickness should be selected according to design pressure, temperature, material strength, corrosion allowance and applicable design code.

4. Select the appropriate material standard

For example, ASTM A53 is commonly used for carbon steel pipe for mechanical and pressure applications as well as steam, water, gas and air lines.

5. Confirm the actual OD and ID

This is particularly important when the pipe must connect to valves, flanges, fittings or existing piping.

6. Confirm dimensional tolerances

The table values represent nominal/reference dimensions. Actual manufactured dimensions are subject to the tolerances specified by the applicable product standard.

FAQ About ERW Carbon Steel Pipe Sizes

1. What are the most common ERW carbon steel pipe sizes?

Common ERW carbon steel pipe sizes include 1/2", 3/4", 1", 1-1/2", 2", 3", 4", 6", 8", 10" and 12". The available size range depends on the applicable manufacturing standard and supplier.

2. What is the OD of a 2-inch ERW carbon steel pipe?

A standard NPS 2 ERW carbon steel pipe has an outside diameter of 60.3 mm (2.375 inches). The OD remains the same for different Schedules, while the wall thickness and ID change.

3. What is the difference between SCH 40 and SCH 80 ERW pipe?

For the same NPS, SCH 80 has a thicker wall than SCH 40. As a result, SCH 80 generally has a smaller internal diameter and higher pipe weight. The appropriate Schedule should be selected based on design requirements rather than Schedule number alone.

4. Does ERW pipe size refer to OD or NPS?

ERW pipe size is normally specified using NPS, not the actual outside diameter. For example, NPS 4 corresponds to an actual OD of 114.3 mm.

5. What is the wall thickness of a 2-inch SCH 40 ERW pipe?

A standard NPS 2 SCH 40 pipe has a nominal wall thickness of 3.91 mm, an OD of 60.3 mm and an approximate ID of 52.48 mm.

Conclusion

ERW carbon steel pipe sizes are primarily identified by NPS, OD, wall thickness, ID and Schedule. SCH 40 and SCH 80 are common choices, but the correct size and wall thickness should be determined from flow requirements, pressure, temperature, material grade, corrosion allowance and applicable standards.

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