Like to get your thoughts on this.

I have two vessels connected by axial expansion bellow/untied bellows(nozzle to nozzle).

The nozzle is 20" and the maximum system pressure is 10 bars. I computed the pressure thrust force for the design of the vessel supports and the structure.

There's a discussion in the office whether the nozzle will take up axial loads due to pressure thrust because the effective area of the expansion joint is greater than the area calculated from the inner diameter of the nozzle. Loads on the nozzle is the difference in area times the maximum pressure.

My opinion is the nozzle won't take any axial load but only compression load on the nozzle neck and flange. Because the system is pressurized and the pressure on the exposed area on the nozzle face is the same as the pressure on the exact same area when I am looking at the nozzle from inside the vessel. Hence the nozzle will not be displace therefore no axial loads on the nozzle-shell interface, only compression of the nozzle elements.

Is my opinion the better way to threat the pressure thrust on the nozzle or should the nozzle be design for the pressure thrust taken as axial loads?

The nozzles will see the only thrust generated by the annular area of convolutions. The thrust due to the 20" 'hole' will react on the far walls of the vessels, then into the foundations, which you have catered for.

There may be some compression of the bellows due to radial expansion and this will cause a force due to the EXJ spring rate, which will react on the flange face.

Edison,

There is a situation like yours presented by Witzenmann. You can find it at www.witzenmann.de the Witzenmann Hydra Expansion Joint manual page 506.
In the example, the two container are connected together by a straight-section tire rod.

I would also reccomend this manual for the persons that want to understand the basis of expansion joints. Very good material.

Best regards,

Sorry, the Witzenmann Hydra Expansion Joint manual can be find at www.flexperte.de

Best regards,