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How to calculate steel pipe allowable pressure?

Calculating Steel Pipe Allowable Pressure According to ASME B31.3

Calculating the allowable pressure for a steel pipe involves considering various factors such as material properties, design temperature, and pipe dimensions. According to the ASME B31.3 Code for Process Piping, Formula is:

P = 2SEt / (D - 2t)

P = Internal design pressure
S = Allowable stress for the material at the design temperature
E = Weld joint efficiency factor
t = Nominal wall thickness of the pipe
D = Outside diameter of the pipe

How to Calculate Steel Pipe Pressure Rate:

1. Determine the Material Allowable Stress (S):
   The allowable stress depends on the material and the design temperature. Refer to the ASME B31.3 tables (Table A-1) to find the allowable stress value for the specific material at the design temperature.

2. Determine the Weld Joint Efficiency (E):
   The weld joint efficiency factor accounts for the type of weld used. Typical values are:
   - Seamless pipe: E = 1.0
   - Longitudinally welded pipe: E = 0.85 (or as specified in the code)

3. Measure the Nominal Wall Thickness (t):
   The nominal wall thickness should be determined, and corrosion allowance should be considered if applicable.

4. Measure the Outside Diameter (D):
   The outside diameter of the pipe must be known.

5. Insert Values into the Formula:
   Substitute the values for S, E, t, and D into the formula to calculate the internal design pressure P.

Example Steel Pipe Allowable Pressure Calculation:

Lets assume the following values for a steel pipe:
- Material: Carbon steel (A106 Gr.B)
- Design Temperature: 200°C (392°F)
- Allowable Stress (S) from ASME B31.3 for A106 Gr.B at 200°C: 20,000 psi
- Weld Joint Efficiency (E): 0.85
- Nominal Wall Thickness (t): 0.5 inches
- Outside Diameter (D): 10 inches

P = (2 x 20000 x 0.85 x 0.5) / (10 - 2 x 0.5)
P = 17000 / 9
P ≈ 1888.89 psi

Thus, the allowable internal design pressure for the specified steel pipe is approximately 1888.89 psi.

Important Notes:

- Ensure all measurements are accurate and all necessary factors such as corrosion allowances and additional code requirements are considered.
- Always refer to the latest version of the ASME B31.3 Code for any updates or changes in the allowable stress values or other parameters.

High Pressure Seamless Stainless Tubing

High Pressure Seamless Stainless Tube

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