ASME B31.3 Pipe Bends

Calculate wall thickness requirements for pipe bends under internal pressure according to ASME B31.3 Process Piping Code. Includes intrados and extrados correction factors.

⚠️ Disclaimer

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 pipe bend calculation. The bend radius (R1) is critical for determining correction factors.

Pipe Geometry & Bend Parameters

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

Bend Radius (R1)

Radius of the pipe bend centerline

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 for pipe bends include correction factors and thickness requirements for both intrados (inside) and extrados (outside) of the bend.

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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 pipe bends under internal pressure.

Key Equations

Intrados factor: I_i = (4R1/D - 1) / (4R1/D - 2)
Extrados factor: I_e = (4R1/D + 1) / (4R1/D + 2)
Inside bend thickness: t_i = PD / (2(SEW/I_i + PY))
Outside bend thickness: t_e = PD / (2(SEW/I_e + PY))
Maximum pressure: P_max = min(P_max_i, P_max_e, P_max_straight)

Code Compliance

Pipe bends require special consideration due to stress concentration. The intrados (inside) typically has higher stress due to the bend geometry, while the extrados (outside) may have reduced stress. This calculator determines the governing thickness requirement.