Hello.

I just want to know if the fluid density is needed in modeling the pressure vessel as a simulation in CAESAR II? Thank you.

If referring to the fluid within the pressure vessel itself, generally, no.

However, fluid within the piping will affect the loads on the nozzles, and thus should be included within the analysis.

Further, if you are performing a full analysis of the nozzle, the design pressure of the vessel should have any hydrostatic head built into it.

Note that this applies to any equipment whose nozzle does not move as a function of fluid density or level. Large tanks do not meet this requirement.

If you need loads on vessel foundation or do seismic analysis, then yes. You need to add fluid density.

Only purpose of Equipment modeling is to calculate the actual deflection of nozzle with respect to the equipment support in operating/design condition. Hence it is not necessary to key in the fluid density for equipment as per my opinion.

Seismic analysis of equipment or equipment support loading is not part of CAESAR II stress analysis.

Natural frequencies will be wrong if you ignore mass of fluid inside vessel