ASME B31.3 Straight Pipe Internal Pressure

Calculate the minimum wall thickness and maximum allowable pressure for a straight pipe under internal pressure according to ASME B31.3 Process Piping Code.

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This calculator is intended exclusively for use by trained professionals. While every effort has been made to ensure the accuracy and reliability of the calculations provided, we do not guarantee that the information is complete, up-to-date, or suitable for any specific purpose. Users must independently verify the results and assume full responsibility for any decisions or actions taken based on its output. Use of this calculator is entirely at your own risk, and we expressly disclaim any liability for errors or omissions in the information provided.

Input Parameters

Enter the design parameters for your straight pipe calculation. All fields are required except mechanical allowances (c), which can be zero.

Pipe Geometry

Design Pressure (P)

Internal design pressure of the pipe

Outside Diameter (D)

Outer diameter of the pipe

Nominal Wall Thickness (T̄)

Nominal (specified) wall thickness

Mechanical Allowances (c)

Sum of corrosion, erosion, and thread allowances

Material & Design Factors

Allowable Stress (S)

Material allowable stress per ASME B31.3

Quality Factor (E)

Quality factor from Table A-1A or A-1B (typically 1.0)

Weld Joint Factor (W)

Weld joint strength reduction factor (typically 1.0)

Mill Undertolerance (Um)

Manufacturing tolerance factor (0-1, typically 0.125)

Y Coefficient

Temperature coefficient from Table 304.1.1 (typically 0.4 for steel)

Calculation Results

The calculated values based on your input parameters. Key results include the minimum required thickness and maximum allowable pressure.

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Export Report

Generate a detailed calculation report with all input parameters, results, and equations in your preferred format.

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About This Calculator

This calculator implements ASME B31.3 Process Piping Code equations for straight pipe under internal pressure.

Key Equations

Pressure design thickness: t = PD / (2(SEW + PY))
Minimum required thickness: t_m = t + c
Actual wall thickness: T = T̄(1 - Um)
Maximum allowable pressure: P_max = 2(T-c)SEW / (D-2(T-c)Y)

Code Compliance

This calculator automatically checks for ASME B31.3 compliance conditions including thick wall criteria (t ≥ D/6) and high pressure ratios (P/(S×E) > 0.385) that require special consideration.