Cast iron pipes are widely used in building drainage systems, industrial pipelines, sewage treatment plants, and municipal infrastructure due to their excellent wear resistance, corrosion resistance, and pressure bearing capacity. Understanding and correctly selecting the right size of cast iron pipes is essential to ensure the stable operation of the system and extend its service life.
Cast Iron Pipe Size Standards
The size of cast iron pipes is usually formulated according to international and domestic standards, such as the ASTM standards in the United States and the GB standards in China. The following are some common cast iron pipe size parameters
1. Diameter
The outer diameter of cast iron pipes usually ranges from 4 inches (about 100 mm) to 60 inches (about 1500 mm). Common standard diameters include:
DN100 (4 inches)
DN150 (6 inches)
DN200 (8 inches)
DN250 (10 inches)
DN300 (12 inches)
DN350 (14 inches)
DN400 (16 inches)
2. Wall thickness
The wall thickness of cast iron pipes varies depending on the required pressure rating and purpose. Common wall thickness standards are shown in the following table:
|
Nominal diameter (DN) |
Outer diameter (mm) |
Wall thickness range (mm) |
|
DN100（4inches） |
100 |
4.5 – 5.5 |
|
DN150（6inches） |
150 |
6.0 – 7.0 |
|
DN200（8inches） |
200 |
7.5 – 9.0 |
|
DN250（10inches） |
250 |
8.5 – 10.0 |
|
DN300（12inches） |
300 |
10.0 – 12.0 |
|
DN350（14inches） |
350 |
11.0 – 13.0 |
|
DN400（16inches） |
400 |
12.0 – 14.0 |
3. Length
The length of standard cast iron pipes is usually 3 meters (about 10 feet), and there are also customized lengths according to customer needs. 3-meter-long pipes are easy to transport and install, reducing the workload of on-site cutting.
4. Weight
|
Nominal diameter (DN) |
Outer diameter (mm) |
Wall thickness (mm) |
Weight (kg/m) |
|
DN100 |
100 |
5.0 |
35 |
|
DN150 |
150 |
6.0 |
60 |
|
DN200 |
200 |
7.0 |
90 |
|
DN250 |
250 |
8.0 |
120 |
|
DN300 |
300 |
10.0 |
160 |
|
DN350 |
350 |
11.0 |
200 |
|
DN400 |
400 |
12.0 |
240 |
Basis for selecting cast iron pipe size
In practical applications, the following factors need to be considered when selecting the right size of cast iron pipe:
Flow demand: Select the diameter of the pipe according to the flow demand of the system to ensure smooth flow and avoid blockage or overflow.
Pressure level: Different applications have different requirements for the pressure bearing capacity of the pipe, and the appropriate wall thickness needs to be selected according to the actual working conditions.
Installation space: The outer diameter of the pipe needs to match the installation environment to avoid installation difficulties due to space limitations.
Material standards: Cast iron pipes that meet national or international standards should be selected to ensure quality and safety.
Length and connection method: Standard length is convenient for transportation and installation, and the connection method (such as socket, flange connection, etc.) must meet the system design requirements.
Cast iron pipe application case
The following is the selection data of cast iron pipes in a municipal sewage treatment project:
Pipeline system: sewage main transmission pipeline
Pipe specification: DN300, outer diameter 300mm, wall thickness 10mm
Flow design: daily design flow 50,000 cubic meters
Pressure level: 0.8 MPa
Pipeline length: 3 kilometers, using a total of 1,000 standard 3-meter cast iron pipes
Total weight: 160 kg/m × 3000 m = 480,000 kg
The efficient operation and long-term stability of the sewage system are ensured by the reasonable selection of DN300 cast iron pipes.
