Selection of Wall Thickness and Pressure Resistance Calculation for Seamless Steel Pipes

For seamless steel pipes, given the outer diameter and wall thickness, we can calculate the maximum pressure the pipe can withstand. Alternatively, if the outer diameter and pressure are known, we can determine the most economical and suitable wall thickness. These two scenarios are commonly encountered by our designers. Here is the calculation formula:

Let the tensile strength of the material be σ, pressure be P, and pipe outer diameter be D;
The pipe wall thickness δ = (P * D) / (2 * σ / S), where S is the safety factor.

For pressure P less than 7 MPa, S = 8; for P between 7 and 10 MPa, S = 6; for P greater than 10 MPa, S = 4.

Example: Calculating the maximum pressure for a φ16*3 seamless steel pipe (20# steel).
Step 1: Choose a safety factor of S = 6 and a tensile strength of 410 MPa for 20# steel.
For φ16*3 seamless steel pipe, the pressure it can withstand is:
P = (2 * σ / S * δ) / D
= (2 * 410 / 6 * 3) / 16
= (calculated value > x)

Therefore, in the second step, choose a safety factor of S = 4:
P = (2 * σ / S * δ) / D
= (2 * 410 / 4 * 3) / 16
= (calculated value)

Real-world design examples:
1. For a GL heater water-mixing pipe, we selected a φ76*4 seamless steel pipe (20# steel).
Step 1: Choose a safety factor of S = 6 and a tensile strength of 410 MPa for 20# steel.
The pressure the pipe can withstand is:
P = (2 * σ / S * δ) / D
= (2 * 410 / 6 * 4) / 76
= (calculated value within range of 7 to x MPa)

Conclusion: The φ76*4 seamless steel pipe can withstand the steam pressure in this project without concern.

2. For the same project, we initially selected a φ18*2 seamless steel pipe (20# steel) for the GL heater heat exchanger. Can this φ18*2 pipe withstand the steam pressure?
Step 1: Choose a safety factor of S = 8 and a tensile strength of 410 MPa for 20# steel.
The pressure it can withstand is:
P = (2 * σ / S * δ) / D
= (2 * 410 / 8 * 2) / 18
= (calculated value > 7 MPa)

Therefore, in the second step, choose a safety factor of S = 6:
P = (2 * σ / S * δ) / D
= (calculated value)

Thus, the φ18*2 seamless steel pipe can handle the steam pressure, so there is no need to select a pipe with a thicker wall.