Dear My Friends,
I will be appreciated if you can answer my question:
According to ASME Code in the calculation formula of a vessel thickness(t=PR/(2SE -0.6P),
I do not know 0.6P is based on theoretical consideration or experimental consideration.
Best Regards,
Naderi

Hello Naderi

A more accurate assessment of the hoop stress in a cylindrical shell is derived using thick cylinder theory (lame theorem). The stress across the thickness of the shell is not the same all the way across the thickness. The stress is actually higher in the inside surface than the outside surface when internal pressure is operating.

To account for this, the 0,6P term is introduced to adjust the formula to more closely resemble the accurate thick cylinder formula.

In the case of very thin cylinders for low pressure usage, the 0,6P component of the equation makes little difference, and could be left out the equation. But when the thickness is more than 10% of the diameter, the term becomes significant.