Seamless steel pipe selection principles and methods

1. Preferred Pipe Material

- Metal Materials First: Priority given to steel pipes; if unsuitable, non-ferrous metals or non-metallic materials are considered.

- Hierarchy within Steel Pipes: Carbon steel first, then stainless steel. For carbon steel, welded pipes are preferred over seamless pipes unless otherwise necessary.

2. Influence of Medium Pressure

High Pressure (Above 1.6 MPa): Use seamless steel or non-ferrous metal pipes. For very high pressures (up to 32 MPa), use high-pressure seamless pipes (20# or 15CrMo).

Medium Pressure (Below 1.6 MPa): Welded steel, cast iron, or non-metallic pipes can be used. Cast iron should not exceed 1.0 MPa.

3. Influence of Medium Temperature

- Hydrogen (1.0 MPa):

Below 350°C: 20# seamless steel pipes.

351-400°C: 15CrMo or 12CrMo seamless steel pipes.

4. Influence of Chemical Properties of Medium

- Neutral Media: Ordinary carbon steel pipes.

- Acidic/Alkaline Media: Acid-resistant or alkali-resistant pipes. The specific material depends on the strength and concentration of the medium.

- Special Cases:

Carbon dioxide in urea plants: Stainless steel.

Fuming sulfuric acid: Carbon steel.

Dilute sulfuric acid: Duralumin.

5. Function of the Steel Pipe

- Additional Functions: Absorbing shocks, accommodating thermal expansion/contraction, frequent movement (e.g., high-pressure steel wire braided hoses for gas applications).

6. Effect of Pressure Drop

- Calculate Pressure Drop: Determine the inner diameter of the pipe and ensure it meets requirements. Adjust based on material flow rate and select a standard steel pipe that matches or slightly exceeds the calculated diameter.