Worked Example: Pipe Wall Thickness Design

This worked example demonstrates how to find the minimum required thickness ( $t_{min}$ ) for a straight pipe under internal pressure using the ASME B31.3 standard.

1. Problem Statement

Calculate the required pressure design thickness ( $t$ ) and the minimum required thickness ( $t_{min}$ ) for a seamless steel pipe operating at a design pressure $P = 400 \text{ psi}$ . The pipe has an outside diameter $D = 10.75 \text{ in}$ (standard 10-inch pipe). The allowable stress of the material at the operating temperature is $S = 20,000 \text{ psi}$ . The pipe is seamless ( $E = 1.0$ ), and the operating temperature dictates $Y = 0.4$ . A corrosion allowance of $c = 0.125 \text{ in}$ is required.

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2. Given Data

Design Pressure (P)

psi

Outside Diameter (D)

Allowable Stress (S)

psi

Quality Factor (E)

Temperature Coefficient (Y)

Corrosion Allowance (c)

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3. Formula and Calculation

Calculate the pressure design thickness ( $t$ ):

Error: Formula chemical-pipe-wall-thickness not found in the Formula Registry.

The required pressure design thickness is $0.1066 \text{ in}$ .

Calculate the minimum required thickness ( $t_{min}$ ): $t_{min} = t + c$ For initial values: $t_{min} = 0.1066 + 0.125 = 0.2316 \text{ in}$

Conclusion: The selected pipe schedule must have a guaranteed minimum thickness greater than $0.2316 \text{ in}$ .

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