Issue 1 V1.08
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Welded Connections > Torsion on Tube/Pipe FP Butt Weld

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Full Penetration Tube Weld Stress

Notation and Units

Metric and Imperial Units

The above welding stress equations may be used with both imperial and metric units. As with all mathematical calculations care must be taken to keep consistent units throughout. Examples of units which could be adopted have been provided below:


  • a = weld throat thickness, in or mm
  • D = tube/pipe outside diameter, in or mm
  • d = effective tube/pipe inside diameter , in or mm
  • T = torque force, or Nmm
  • Zw = modulus of weld section, in3 or mm3
  • τ|| = shear stress parallel to weld direction, psi or MPa