Tanks vs pressure vessels in earthquake calculations

[Mark Cr]

I'm using Eurocode 8 - part 1 for seismic calculations of a pressure vessel, but our customer is asking us for using Eurocode 8 - part 4 (section "Tanks") for the seismic calculation, something that my software doesn't have.

Is it right to ask for using the section "tanks" for a pressure vessel?
Is there any norm (better european) that defines what is a tank and what a pressure vessel in order to see the differences between the two concepts?
Is there any software to carry out seismic calculations of a pressure vessel supported on legs taking into account impulsive, convective and vertical stresses of the fluid moving inside the vessel because of an earthquake?

[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 .

[fernandovz]

Hi, I does not know the Eurocode, but earthquake calculations for tanks and pressure vessel are different. For tanks there are convective and impulsive mass which will be inappropriate to consider in a pressure vessel. I think you are OK and you shall argue your position.

[gerge22]

Are You doing only earthquake calculation or are You doing the entire design ( thickness and nozzles ) ?

[Mark Cr]

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

[Mark Cr]

We are making the entire design: thicknesses and nozzles. Only piping between different vessels is a matter of other companies.

[gerge22]

then according to what standard are you doing the thickness calculation? asme or SR EN 13445 ?
SR EN 13445 clearly states that it covers unfired PRESSURE VESSELS with a maximum allowable pressure bigger then 0.5 bar.
Asme Section VIII Division 1 - Provides requirements applicable to the design, fabrication, inspection, testing, and certification of pressure vessels operating at either internal or external pressures exceeding 15 psig.
From what you are telling me ( pressure design 10-26 bar ) i would certainly qualify these as pressure vessels.