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What is the ASME B31.3 pipe wall thickness formula?

ASME B31.3 Paragraph 304.1.2 Eq (3a): t_m = (P × D) / (2 × (S × E + P × 0.4)) + CA, where P is design pressure, D is outside diameter, S is allowable stress, E is quality factor, and CA is corrosion allowance.

What is the quality factor (E) in ASME B31.3?

The quality factor E accounts for manufacturing method. For seamless pipe, E = 1.0. For furnace butt-welded pipe, E = 0.60. For electric resistance welded (ERW) pipe, E = 0.85. Refer to ASME B31.3 Table A-1B for specific values.

What corrosion allowance should be used for carbon steel pipe?

Typical corrosion allowance for carbon steel in process piping is 0.0625 inches (1.6 mm) for non-corrosive service, 0.125 inches (3.2 mm) for mildly corrosive service, and 0.25 inches (6.4 mm) for severely corrosive service. The actual value depends on the service environment.

What is the difference between Schedule 40 and Schedule 80 pipe?

Schedule 80 pipe has a thicker wall than Schedule 40 for the same nominal diameter. For 6-inch pipe, Schedule 40 wall is 0.280 in and Schedule 80 wall is 0.432 in. Schedule 80 is used for higher pressures or when corrosion allowance requires additional thickness.

pipe wall thickness · Engineering Calculator

ASME B31.3 Pipe Wall Thickness Calculator for Carbon Steel at 1480 psig

Formula

t_m = (P × D) / (2 × (S × E + P × 0.4)) + CA

Governing Standard

ASME B31.3 Process Piping — Paragraph 304.1.2, Eq (3a)

Required Inputs

Design Pressure (P) in psig
Outside Diameter (D) in inches
Allowable Stress (S) in ksi
Quality Factor (E) — 1.0 for seamless
Corrosion Allowance (CA) in inches

Output

Minimum Required Wall Thickness (t_m) in inches

Notes

For 6-inch Schedule 40 carbon steel pipe (D=6.625 in) at P=1480 psig, S=16.7 ksi, E=1.0, CA=0.0625 in: t_m = (1480 × 6.625) / (2 × (16700 + 592)) + 0.0625 = 0.281 + 0.0625 = 0.344 in. Schedule 40 wall thickness is 0.280 in — this is INADEQUATE. Schedule 80 (0.432 in) is required.

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