Spiral steel pipe is a kind of steel pipe made by rolling a steel strip into a pipe shape at a certain spiral angle (forming angle) and then welding it. It is widely used in pipeline systems for oil, natural gas and water transmission.
Nominal Diameter (DN)
Nominal diameter refers to the nominal diameter of a pipe, which is a nominal value of the pipe size. For spiral steel pipe, the nominal diameter is usually close to, but not equal to, the actual inside or outside diameter.
It is usually expressed by DN plus a number, such as DN200, which indicates that the nominal diameter is 200 mm steel pipe.
Common nominal diameter (DN) ranges:
1. Small diameter range (DN100 - DN300):
DN100 (4 inches)
DN150 (6 inches)
DN200 (8 inches)
DN250 (10 inches)
DN300 (12 inches)
2. Medium diameter range (DN350 - DN700):
DN350 (14 inches)
DN400 (16 inches)
DN450 (18 inches)
DN500 (20 inches)
DN600 (24 inches)
DN700 (28 inches)
3. Large diameter range (DN750 - DN1200):
DN750 (30 inches)
DN800 (32 inches)
DN900 (36 inches)
DN1000 (40 inches)
DN1100 (44 inches)
DN1200 (48 inches)
4. Extra large diameter range (DN1300 and above):
DN1300 (52 inches)
DN1400 (56 inches)
DN1500 (60 inches)
DN1600 (64 inches)
DN1800 (72 inches)
DN2000 (80 inches)
DN2200 (88 inches)
DN2400 (96 inches)
DN2600 (104 inches)
DN2800 (112 inches)
DN3000 (120 inches)
OD and ID
Outer Diameter (OD):
OD is the diameter of the outer surface of the spiral steel pipe. The OD of a spiral steel pipe is the actual size of the outside of the pipe.
The OD can be obtained by actual measurement and is usually measured in millimeters (mm).
Internal Diameter (ID):
ID is the inner surface diameter of the spiral steel pipe. The ID is the actual size of the inside of the pipe.
ID is usually calculated from the OD minus twice the wall thickness in millimeters (mm).
ID=OD-2×wall thickness
Typical applications
Spiral steel pipes with different nominal diameters have different applications in various fields:
1. Small diameter spiral steel pipe (DN100 - DN300):
Commonly used in municipal engineering for water supply pipes, drainage pipes, gas pipes, etc.
2. medium diameter spiral steel pipe (DN350-DN700): widely used in oil, natural gas pipeline and industrial water pipeline.
3. large diameter spiral steel pipe (DN750 - DN1200): used in long-distance water transmission projects, oil pipelines, large-scale industrial projects, such as medium transportation.
4. super large diameter spiral steel pipe (DN1300 and above): mainly used for cross-regional long-distance water, oil and gas pipeline projects, submarine pipelines and other large-scale infrastructure projects.
Standards and norms
The nominal diameter and other specifications of spiral steel pipe are usually produced in accordance with the relevant standards and norms, such as:
1. International standards:
API 5L: applicable to pipeline transportation steel pipe, stipulates the size and material requirements of spiral steel pipe.
ASTM A252: applicable to structural steel pipe, the size of the spiral steel pipe and manufacturing requirements.
2. National Standard:
GB/T 9711: applicable to steel pipe for oil and gas industry transportation, specifies the technical requirements of spiral steel pipe.
GB/T 3091: applicable to low-pressure fluid transportation with welded steel pipe, specifies the spiral steel pipe size and technical requirements.
Post time: Jul-15-2025
