ERW Pipe Specifications and Models

1. ERW Pipe Size Chart

ERW Pipe comes in a variety of sizes, ranging from ½ inch to 16 inches. Each size has its own technical specifications, including outer diameter, wall thickness, and tolerances. Wall thickness must meet certain standards, such as ASTM A53, which stipulates a maximum wall thickness of 12.5% of the pipe's outer diameter.

The table below shows the standard dimensions and wall thickness ranges of ERW steel pipes based on common pipe schedules. All values are provided in millimeters (mm), with nominal sizes in inches (NPS).

Nominal Pipe Size (NPS)			Nominal Wall Thickness (mm)
DN	NPS	OD (mm)	Sch10	Sch20	Sch30	STD	Sch40	Sch60	XS	Sch80
15	1/2	21.3	2.11	-	2.41	2.77	2.77	-	3.73	3.73
20	3/4	26.7	2.11	-	2.77	2.87	2.87	-	3.91	3.91
25	1	33.4	2.77	-	2.90	3.38	3.38	-	4.55	4.55
32	1¼	42.2	2.77	-	3.18	3.56	3.56	-	4.85	4.85
40	1½	48.3	2.77	-	3.68	3.68	3.68	-	5.08	5.08
50	2	60.3	2.77	-	3.91	3.91	3.91	-	5.54	5.54
65	2½	73.0	3.05	-	4.78	5.16	5.16	-	7.01	7.01
80	3	88.9	3.05	-	4.78	5.49	5.49	-	7.62	7.62
90	3½	101.6	3.05	-	5.74	5.74	5.74	-	8.08	8.08
100	4	114.3	3.05	-	4.78	6.02	6.02	-	8.56	8.56
125	5	141.3	3.40	-	6.55	6.55	6.55	-	9.53	9.53
150	6	168.3	3.40	-	7.11	7.11	7.11	-	10.97	10.97
200	8	219.1	3.76	6.35	7.04	8.18	8.18	10.31	12.70	12.70
250	10	273.0	4.19	6.35	7.80	9.27	9.27	12.70	12.70	-
300	12	323.9	4.57	6.35	8.38	9.53	9.53	-	12.70	-
350	14	355.6	6.35	7.92	9.53	9.53	11.13	-	12.70	-
400	16	406.4	6.35	7.92	9.53	9.53	14.27	-	12.70	-
450	18	457.0	6.35	7.92	11.13	11.13	14.27	-	12.70	-
500	20	508.0	6.35	9.53	12.70	12.70	15.09	-	12.70	-
550	22	559.0	6.35	9.53	12.70	12.70	17.48	-	12.70	-
600	24	610.0	6.35	9.53	14.27	14.27	17.48	-	12.70	-

2. Common ERW Pipe Sizes

In practical applications, only a limited range of ERW pipe sizes are used frequently. The selection usually depends on the industry and operating conditions.

- Oil and Gas Industry

Common sizes: NPS 2" to 8" (DN50–DN200)

Typically used for medium-pressure pipelines and transmission systems.

- Water Supply and Drainage

Common sizes: NPS 1" to 6" (DN25–DN150)

Suitable for municipal water systems, irrigation, and industrial fluid transport.

- Construction and Structural Applications

Common sizes: NPS 2" to 12" (DN50–DN300)

Used in scaffolding, steel structures, and mechanical frameworks.

For larger diameter requirements (above NPS 16"), welded pipes such as spiral welded pipes are more commonly used.

3. Standards and Grades

ERW steel pipes are manufactured according to a range of international standards, depending on the application and performance requirements. The most commonly used standards include API, ASTM, and EN specifications.

(1) API 5L (Line Pipe Standard)

Widely used in oil and gas transmission systems. Common grades include Grade B, X42, and X52, offering different strength levels for pipeline applications.

(2) ASTM A53 (General Purpose Pipe)

Typically used for mechanical and pressure applications such as water, gas, and steam transport. Grade B is the most commonly used material.

(3) EN 10219 (Structural Hollow Sections)

Used mainly in construction and structural applications. Common grades include S235 and S355, with defined mechanical properties.

4. Dimensions and Tolerances

The key dimensional parameters of ERW steel pipes include outer diameter (OD), wall thickness (WT), and allowable tolerances. These factors directly affect the pipe's pressure capacity and application performance.

4.1 Outer Diameter (OD)

The outer diameter defines the overall size of the pipe and is standardized according to nominal pipe size (NPS). It remains constant regardless of wall thickness.

4.2 Wall Thickness (WT)

Wall thickness determines the strength and pressure rating of the pipe. It is commonly specified by schedule numbers (e.g., Sch10, Sch40, Sch80), where higher schedules indicate thicker walls.

4.3 Tolerance

Manufacturing tolerances define the acceptable variation in OD and WT. According to standards such as ASTM A53, wall thickness tolerance is typically controlled within a specified percentage range to ensure performance consistency.

For example:

- NPS 6" (DN150)

- Outer Diameter: 168.3 mm

- Wall Thickness (Sch40): 7.11 mm

This combination is commonly used in medium-pressure pipeline systems.

5. Weight Calculation of ERW Pipe

ERW pipe is typically sold and evaluated based on weight per unit length, making it important to understand how pipe weight is calculated. The weight depends on the pipe’s outer diameter (OD), wall thickness (WT), and material density.

The weight of ERW pipe (per unit length) can be calculated using the following formula:

W = 0.02466 × (D − t) × t

Where:

W = Weight (kg/m)

D = Outside Diameter (mm)

t = Wall Thickness (mm)

For example, a 6" (DN150) Sch40 ERW pipe has: Outer Diameter 168.3mm, Wall Thickness 7.11mm → Weight approximately 22.85 kg/m

6. How to Select ERW Pipe Specifications

Selecting ERW pipe is not just about choosing a size. In practice, it mainly depends on pressure conditions, application, and the required standard.

6.1 Based on Pressure

Wall thickness is directly related to pressure capacity. For higher pressure systems, thicker wall pipes are required to maintain safety margins.

In practice, lighter schedules such as Sch10 or Sch20 are used for low-pressure systems, while Sch40 is commonly seen in general industrial pipelines. For more demanding conditions, higher schedules like Sch80 are typically specified.

6.2 Based on Application

Different applications place different requirements on the pipe.

For example, in oil and gas transmission, pipes are expected to meet stricter strength and inspection requirements, so API 5L grades are commonly used.

For water systems, standard carbon steel pipes such as ASTM A53 are usually sufficient, unless corrosion or special conditions are involved.

In structural use, the focus is less on pressure and more on mechanical performance and dimensional consistency.

6.3 Based on Standard

In practice, the standard is often defined by the project rather than selected freely.

API standards are typically specified for pipeline projects, while ASTM is widely used for general industrial purposes. EN standards are more common in structural and European projects.

Once the standard is fixed, size range, tolerance, and testing requirements are usually determined accordingly.

6.4 Other Practical Considerations

Coating type, testing requirements, installation conditions, and connection methods all affect the final selection. These factors are usually defined by the project environment rather than the pipe itself.

7. ERW Pipe vs Seamless Pipe

In practice, ERW and seamless pipes are often considered for similar applications, but the choice depends on pressure requirements, safety margin, and cost.

How to Choose in Practice

In most conventional applications, ERW pipe is already sufficient and is often used as the default option. It covers a wide range of sizes, is readily available, and helps keep overall project cost under control.

Seamless pipe is typically specified when operating conditions become more demanding — for example, higher pressure, temperature variation, or systems with stricter inspection requirements.

Read full comparison: ERW vs Seamless Pipe

8. FAQs

Q1：What is ERW pipe used for?

ERW pipes are widely used in water transmission, general pipelines, structural members, and industrial systems.

In most standard conditions, they are considered a practical and economical choice.

Q2：Is ERW pipe strong?

Under standard specifications, yes.

ERW pipes can achieve stable mechanical performance and are suitable for most pressure and structural applications when properly manufactured and tested.

Q3：ERW vs seamless — which is better?

This depends on the operating conditions.

ERW pipe is generally preferred for cost efficiency and availability, while seamless pipe is used when higher performance under stress is required.

In most projects, the choice is defined by specification rather than preference.

Q4：What are ERW pipe size standards?

ERW pipe dimensions are defined by standards such as API, ASTM, and EN.

These standards specify outer diameter, wall thickness, tolerance, and testing requirements.

Q5：Can ERW pipe be used for high-pressure systems?

It can, within certain limits.

With appropriate wall thickness and compliance with relevant standards, ERW pipes are used in many medium to high-pressure applications.

For more demanding conditions, seamless pipe is often selected to provide additional safety margin.

9. Related Resources

(1) Learn More About ERW Pipe

What is ERW Pipe

What Does ERW Mean in Welding

(2) Compare with Other Pipe Types

ERW vs Seamless Pipe

ERW vs SSAW Pipe

(3) Technical and Production Insights

ERW Pipe Manufacturing Process

ERW Pipe Quality Control