ERW pipes are widely used in construction, oil & gas, water transmission, and structural applications. One of the most critical factors when selecting ERW pipes is understanding outer diameter (OD) and wall thickness, as these directly affect pressure capacity, strength, weight, and compliance with international standards.This guide provides a comprehensive overview of ERW pipe OD and wall thickness, including standards, size ranges, schedules, and selection tips.
Table 1: Small Diameter ERW Pipe Outer Diameter and Wall Thickness Specifications (Outer Diameter ≤ 114mm)
Table 2: Specifications of Medium and Large Diameter ERW Pipes (Outer Diameter 114-508mm)
Note: The wall thickness values above are for common specifications; non-standard wall thicknesses can be customized according to requirements during actual production. For large-diameter ERW pipes (outer diameter > 508mm), LSAW (longitudinal submerged arc welding) is often used, while the ERW process mainly covers small and medium-diameter ranges.
The nominal diameter of ERW pipes is usually expressed in inches, but the actual outer diameter is measured in millimeters. This "inch-based naming, metric dimensions" system stems from the common practice of international standards (such as API standards). For example, an ERW pipe with a nominal diameter of 6 inches has an actual outer diameter of 168.3 mm, not 152.4 mm (6 × 25.4), because the standard takes into account factors such as pipe end processing and fitting connections.
2. Wall Thickness Series
The wall thickness of ERW pipes is usually divided into the following series:
SCH series: such as SCH40, SCH80, SCH160, etc., where a larger number indicates a thicker wall and stronger pressure bearing capacity.
Standard Wall Thickness (STD): Regular pressure rating
Extra Heavy Wall Thickness (XS/XH): Used for high pressure or special working conditions
Non-standard Wall Thickness: Customized according to engineering requirements
For different nominal diameters, the actual wall thickness corresponding to the same SCH number is different. For example, the wall thickness of SCH40 is 3.91 mm in a 2-inch pipe and 8.18 mm in an 8-inch pipe.
3. Steel Grade and Wall Thickness Limitations
The selection of ERW pipe wall thickness needs to consider the steel grade (material strength):
Low steel grades (such as Q235, L245): Wider wall thickness range, up to 25 mm or more
High steel grades (such as X70, X80): Due to welding process limitations, the maximum wall thickness usually does not exceed 16 mm (small diameter) or 22 mm (large diameter)
Special steel grades: Such as low-temperature steel, corrosion-resistant steel, etc., the wall thickness specifications need to be determined according to specific standards.
ASTM A53 / A500
Used for structural and pressure applications
API 5L ERW Pipe
Common in oil and gas pipelines (Grades B, X42–X70)
EN 10219 / EN 10217
European standards for structural and pressure pipes
Typical tolerances:
OD: ±0.5% to ±1.0%
Wall thickness: ±10% (depending on standard)
2. ERW welded pipes are easier to quality control, resulting in high dimensional accuracy and smaller deviations in outer diameter and wall thickness.
3. Excellent toughness, superior resistance to crushing and bursting, low carbon, sulfur, and phosphorus content, and significantly improved impact toughness.
4. ERW casing pipes use hot-rolled coil plates, resulting in high grain size and structural density of the pipe blank, superior to seamless pipes.
5. In terms of price, ERW steel pipes are also quite competitive and have a long service life.
ERW Pipe Outer Diameter and Wall Thickness Specifications Table
The following is a table showing common outer diameter and wall thickness specifications for ERW pipes, compiled based on standards such as API 5L and GB/T 3091. It should be noted that actual specifications may vary slightly depending on the manufacturer, steel grade, and standard system used. For specific applications, the product standard or purchase contract should be consulted.Table 1: Small Diameter ERW Pipe Outer Diameter and Wall Thickness Specifications (Outer Diameter ≤ 114mm)
| Nominal Size (inch) | Outside Diameter (mm) | Common Wall Thickness Range (mm) | Standard Wall Thickness Series (mm) |
| 1/2" | 21.3 | 2.0 – 4.0 | 2.77, 3.73, 4.78 |
| 3/4" | 26.7 | 2.5 – 5.0 | 2.87, 3.91, 5.56 |
| 1" | 33.4 | 3.0 – 6.0 | 3.38, 4.55, 6.35 |
| 1-1/4" | 42.2 | 3.5 – 6.5 | 3.56, 4.85, 6.35 |
| 1-1/2" | 48.3 | 3.5 – 7.0 | 3.68, 5.08, 7.14 |
| 2" | 60.3 | 3.5 – 8.5 | 3.91, 5.54, 8.74 |
| 2-1/2" | 73 | 4.0 – 10.0 | 5.16, 7.01, 9.53 |
| 3" | 88.9 | 4.5 – 12.0 | 5.49, 7.62, 11.13 |
| 3-1/2" | 101.6 | 5.0 – 12.5 | 5.74, 8.08 |
| 4" | 114.3 | 5.0 – 14.0 | 6.02, 8.56, 13.49 |
Table 2: Specifications of Medium and Large Diameter ERW Pipes (Outer Diameter 114-508mm)
| Nominal Size (inch) | Outside Diameter (mm) | Common Wall Thickness Range (mm) | Standard Wall Thickness Series (mm) |
| 5" | 141.3 | 5.5 – 16.0 | 6.55, 9.53, 15.88 |
| 6" | 168.3 | 6.0 – 18.0 | 7.11, 10.97, 18.26 |
| 8" | 219.1 | 7.0 – 23.0 | 8.18, 12.70, 23.01 |
| 10" | 273 | 8.0 – 28.0 | 9.27, 15.09, 28.58 |
| 12" | 323.8 | 9.0 – 33.0 | 10.31, 17.48, 33.32 |
| 14" | 355.6 | 9.5 – 19.0 | 9.53, 11.13, 19.05 |
| 16" | 406.4 | 9.5 – 22.0 | 9.53, 12.70, 22.00 |
| 18" | 457 | 10.0 – 25.0 | 10.00, 14.30, 25.00 |
| 20" | 508 | 11.0 – 28.0 | 11.10, 15.90, 28.00 |
Note: The wall thickness values above are for common specifications; non-standard wall thicknesses can be customized according to requirements during actual production. For large-diameter ERW pipes (outer diameter > 508mm), LSAW (longitudinal submerged arc welding) is often used, while the ERW process mainly covers small and medium-diameter ranges.
Specifications System Description
1. Relationship between Nominal Diameter and Outer DiameterThe nominal diameter of ERW pipes is usually expressed in inches, but the actual outer diameter is measured in millimeters. This "inch-based naming, metric dimensions" system stems from the common practice of international standards (such as API standards). For example, an ERW pipe with a nominal diameter of 6 inches has an actual outer diameter of 168.3 mm, not 152.4 mm (6 × 25.4), because the standard takes into account factors such as pipe end processing and fitting connections.
2. Wall Thickness Series
The wall thickness of ERW pipes is usually divided into the following series:
SCH series: such as SCH40, SCH80, SCH160, etc., where a larger number indicates a thicker wall and stronger pressure bearing capacity.
Standard Wall Thickness (STD): Regular pressure rating
Extra Heavy Wall Thickness (XS/XH): Used for high pressure or special working conditions
Non-standard Wall Thickness: Customized according to engineering requirements
For different nominal diameters, the actual wall thickness corresponding to the same SCH number is different. For example, the wall thickness of SCH40 is 3.91 mm in a 2-inch pipe and 8.18 mm in an 8-inch pipe.
3. Steel Grade and Wall Thickness Limitations
The selection of ERW pipe wall thickness needs to consider the steel grade (material strength):
Low steel grades (such as Q235, L245): Wider wall thickness range, up to 25 mm or more
High steel grades (such as X70, X80): Due to welding process limitations, the maximum wall thickness usually does not exceed 16 mm (small diameter) or 22 mm (large diameter)
Special steel grades: Such as low-temperature steel, corrosion-resistant steel, etc., the wall thickness specifications need to be determined according to specific standards.
ERW Pipe Standards and Size Tolerances
Different standards define OD and wall thickness tolerances:ASTM A53 / A500
Used for structural and pressure applications
API 5L ERW Pipe
Common in oil and gas pipelines (Grades B, X42–X70)
EN 10219 / EN 10217
European standards for structural and pressure pipes
Typical tolerances:
OD: ±0.5% to ±1.0%
Wall thickness: ±10% (depending on standard)
Performance Characteristics of ERW Pipes:
1. The most significant feature is high production efficiency and fast heating speed, without the need for filler metal.2. ERW welded pipes are easier to quality control, resulting in high dimensional accuracy and smaller deviations in outer diameter and wall thickness.
3. Excellent toughness, superior resistance to crushing and bursting, low carbon, sulfur, and phosphorus content, and significantly improved impact toughness.
4. ERW casing pipes use hot-rolled coil plates, resulting in high grain size and structural density of the pipe blank, superior to seamless pipes.
5. In terms of price, ERW steel pipes are also quite competitive and have a long service life.
