i usually insert pressure as barg (gauge), not as bara (absolute).

now i have a line having a light vacuum inside: 7,0 mbara.

what value have i to insert? if atmospheric pressure is 1bar, then i should insert -0.993 bara?

does caesar accept negative pressure? if yes, having an axial expansion joint without tie rods, will caesar consider pressure forces that will try to "close" the expansion joint (usually positive pressure try to "open" it)?

Hi Vermaccio,

I believe negative pressure(vacuum) is not address in beam element software. You have to evaluate it separately using some guidelines from ASME addressing external pressure (buckling collapse).

Is your line will constantly operate in vacuum or is it only occasional?

Make sure to put in your datasheet of expansion joint that it will be subjected to vacuum, so vendor will consider it in design.

Warm Regards,

Negative pressure is considered in the expansion joint.
If you do a simple model it will be better. A single vertical element, with a big diameter. This element is epansion joint element, add an anchor at bottom.
Put two pressures P1= -0.9 bar, P2=+0.9 bar. Run only P1 and P2 loadcases and see the displacements in the upper node. for P1 will be negative, for P2 will be positive.
Regards,

thank you.

but...

7.0 mbara: how do i insert it? as -0.997 barg?

barg= bara-1 so

-0.993