Pipe wall thickness calculation method for t≥D/6 or for P/SE>0.385

[Sean_Wei]

Hello there,

ASME B31.3 eq. (3a) or eq. (3b) below is for t＜D/6, while for t ≥ D/6 or for P/SE > 0.385, the standard only said “require special consideration of factors such as theory of failure,effects of fatigue, and thermal stress”. How should I calculate it when in this situation？



Thanks

 

[1503-44]

 

[GD2]

A comparable analogy can be found in ASME Sec VIII Div 1 Mandatory Appendix 1 for Cylindrical Shell.

 

[goutam_freelance]

You can try to use Sec VIII Div 3 which caters to high pressures. Even though piping is outside its scope, it is permitted to design as per this code and get a U3 stamp if necessary.

Even though formulae for stresses in thick walled cylinders are available, the complications will arise due to the following:

1. Steady thermal stresses due to unequal temperatures between inside and outside surfaces.
2. Unsteady thermal stresses during heating or cooling and the resulting stress cycles contributing to fatigue.
3. The allowable stress(which failure theory to use etc.)