ASME B31.3 Branch Connection Analysis

Analyze welded branch connections for adequate reinforcement according to ASME B31.3 Process Piping Code. Calculate required and available reinforcement areas.

⚠️ 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.

System Parameters

Enter the design pressure and branch angle for the connection.

Design Pressure (P)

Internal design pressure of the system

Branch Angle (β)

Angle between branch and run pipe centerlines

Header (Run) Pipe Parameters

Enter the parameters for the main run pipe that will receive the branch connection.

Geometry & Material Properties

Outside Diameter (D)

Outer diameter of the header pipe

Nominal Wall Thickness (T̄)

Nominal wall thickness of the header pipe

Mill Undertolerance (Um)

Manufacturing tolerance factor (0-1, typically 0.125)

Mechanical Allowances (c)

Sum of corrosion, erosion, and thread allowances

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)

Y Coefficient

Temperature coefficient from Table 304.1.1 (typically 0.4 for steel)

Branch Pipe Parameters

Enter the parameters for the branch pipe that will be connected to the header.

Geometry & Material Properties

Outside Diameter (D)

Outer diameter of the branch pipe

Nominal Wall Thickness (T̄)

Nominal wall thickness of the branch pipe

Mill Undertolerance (Um)

Manufacturing tolerance factor (0-1, typically 0.125)

Mechanical Allowances (c)

Sum of corrosion, erosion, and thread allowances

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)

Y Coefficient

Temperature coefficient from Table 304.1.1 (typically 0.4 for steel)

Reinforcement Pad Parameters (Optional)

Enter parameters for a reinforcement pad if used. Leave values at 0 if no pad is used.

Outside Diameter (Dr)

Outer diameter of the reinforcement pad (0 if no pad)

Thickness (T̄r)

Nominal thickness of the reinforcement pad (0 if no pad)

Mill Undertolerance (Um,r)

Manufacturing tolerance factor for pad (0-1, typically 0)

Allowable Stress (Sr)

Material allowable stress for pad (0 if no pad)

Weld Parameters

Enter weld dimensions and properties for the connection.

Weld Leg, Branch (zb)

Weld leg size between branch and header pipe (0 if no credit taken)

Weld Leg, Reinforcement (zr)

Weld leg size between pad and header pipe (0 if no pad)

Max Weld Throat (tc,max)

Maximum allowable weld throat thickness

Calculation Results

Analysis results for branch connection reinforcement requirements.

Enter values above to see calculated results

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 requirements for branch connection reinforcement.

Key Equations

A1 = Required reinforcement area
A2 = Area available in run pipe
A3 = Area available in branch pipe
A4 = Area available from reinforcement
Must satisfy: A2 + A3 + A4 ≥ A1

Code Compliance

Branch connections must provide adequate reinforcement to compensate for material removed from the run pipe. This calculator determines the required reinforcement area and compares it to available reinforcement from the run pipe, branch pipe, reinforcement pad, and welds.