How to calculate the thickness Required for the Square or Rectancular vessel subjected to internal & External pressure..?????

Thank you for your answer.

Please refer Appendix 13 of ASME section VIII DIV 1.

_________________
Makrand Pandurang Sakpal,
Static Equipment Design,
makrands9@gmail.com,
Ph no:- 9967949656.

For external pressure case, I would try to demonstrate what comes first: plastic collapse or excess bending stresses. If the latter (almost certainly)- I would use App13 as well. I presume that the vessel is not supported by ribs/stays.
Konrad

_________________
Konrad Anikiel