Tanks vs pressure vessels in earthquake calculations

[gerge22]

What is your design pressure? Is it bigger or smaller then 0.5 bar?
If you are using PED in your design , you could argue that because your vessel has a design pressure bigger then 0.5 bar it is a pressure vessel.
In my opinion if you have a pressure smaller that 0.5 bar then you have a tank .

[Mark Cr]

Thank you! The design pressure of the vessels (there are five in question) range between 10 bar to 26 bar.