Seamless Steel Pipe Size Chart – OD, Wall Thickness

3.2 Boiler Tube Size Range

3.3 Heat Exchanger Tube Dimensions

3.4 Precision Tube Size Range

3.5 Hydraulic Tube Size Range

4. Factors Affecting Seamless Steel Pipe Sizes

4.1 Rolling Process Parameters

The piercing mill's rolling angle and rolling speed directly affect the pipe's outer diameter accuracy. The reduction and number of rolling passes during cold rolling determine wall thickness variation. Fluctuations in process parameters can also lead to dimensional deviations.

4.2 Raw Material Quality

The diameter, roundness, and material uniformity of the tube billet are all transferred to the finished product. If the tube billet exhibits ovality, it can easily result in an out-of-round outer diameter of the steel pipe.

4.3 Temperature Control

Excessively high or uneven heating temperatures can cause inconsistent tube billet deformation, and differences in cooling rates can cause dimensional shrinkage deviations, especially in high-precision cold-drawn tubes.

4.4 Equipment Accuracy

Mechanical clearances and die wear in equipment such as rolling mills and sizing mills directly affect the consistency of pipe diameter and wall thickness. Older equipment can exacerbate dimensional fluctuations.

4.5 Subsequent Processing

Improper operation in processes such as straightening and cutting can lead to deviations in pipe straightness or length.

5. Dimensional Requirements for Seamless Steel Pipes in Different Industries

5.1 Oil and Gas Industry

Large-diameter (219-1422mm) and thick-walled (6-20mm) seamless steel pipes meet high-pressure, long-distance transportation requirements and reduce joints.

5.2 Chemical Industry

Mostly medium-diameter (25-377mm) with a wall thickness of 5-16mm. Seamless stainless steel pipes are often used for corrosive media, while small-diameter (10-50mm) pipes can be used for low-pressure applications.

5.3 Power Industry

Seamless boiler pipes have an outer diameter of 32-426mm and a wall thickness of 2.5-20mm. High-pressure boilers require thicker wall thicknesses, complying with GB5310 standards.

5.4 Mechanical Manufacturing

Mainly seamless precision pipes with an outer diameter of 6-200mm and a wall thickness of 0.5-10mm. Dimensional tolerances are strictly required (within ±0.1mm).

5.5 Construction Industry

Small-diameter (20-50mm, wall thickness 1-3mm) seamless pipes are used for decoration, while large-diameter (159-630mm, wall thickness 5-15mm) seamless pipes are used for structural support.

6. Typical Seamless Pipe Size Selection in Practice

6.1 For General Industrial Piping

In most conventional industrial systems, SCH40 pipes are commonly used as a default choice, with diameters typically ranging from DN25 to DN150 depending on flow requirements.

6.2 For High Pressure or High Temperature Systems

For high-pressure or elevated temperature applications (such as boilers or steam lines), SCH80 or SCH160 pipes are typically specified, often using ASTM A106 standards.

6.3 For Oil & Gas Transmission

In oil and gas transportation, large diameter pipes (DN200 and above) with thicker wall schedules (SCH40–SCH160) are commonly used to ensure strength and long-distance reliability.

6.4 For Precision or Hydraulic Systems

Precision and hydraulic tubes usually use small diameters (≤120 mm) with thin walls, focusing on dimensional accuracy rather than high pressure resistance.