Double gimbal expansion joint for tank settlement

Normally we use lateral expansion joint(universal tied type) for tank settlement. Considering the tank nozzle bending moment due to hydraulic pressure, I think double gimbal expansion joint will be better for large size nozzle loads. Anyone who has used the double gimbal expansion joint for tank nozzle? Please asvise. Site photos are preferred.

It's unclear if you're referring to large nozzles with loads or nozzles with large loads. I'll assume you mean the latter.

If you have one expansion joint with stiffness k, and then compare it to two expansion joints with stiffness k installed in series, then the effective resistance is (sum(k^-1))^-1, or k/2.

So, yes, two expansion joints are better than one. But they're also more expensive and themselves add weight.

You mentioned tank settlement and nozzle bulge, but thermal expansion is often a concern, too.

Tank nozzle expansion joints (or ball joints) should themselves be generally installed perpendicular to the nozzle, since that configuration is the only one that addresses displacement from all three sources. But putting all things in perspective, displacement hasn't been defined here.

Thank you Michael, I agree with you.
I just want to know who has the experience to use the double gimbal expansion joint on tank nozzle. I think it does work but seems almost never be used in this kind of situation.

Older post but some comments

Gimbal unit is expensive and heavy especially where the pressure thrust is high either due to pressure or size or both. Universal is relatively cheap compared to gimbal units. Double gimbal requires more space.

Both types, e.g. universal having 2 bellows elements and double gimbal can have lateral movement in all directions. External axial movement is zero excluding the rod expansion if the rods go over both bellows elements. If there are two sets of rods the center pipe expansion has to be considered in a same way as for the double gimbal.

There is a difference in rotation. If the universal has 3 or more rods all rotation is prevented. If universal has 2 rods then the ends can rotate around one axis. Take 2 sticks in vertical and try to balance a plate on top of them. Take 3 sticks and try again. Expansion joint works the same.

Gimbal unit can rotate in all directions, e.g. one stick supporting the plate.

CAESAR II modelling for the universal has to be correct. Do not use simple modelling for 2 rod case. If you do the result is wrong. You do need to use comprehensive modelling so that the ends are free to rotate around one axis.

When you use 2 rods you have to make sure that the rod orientation is given on the drawing. I had a case where original rod orientation on turbine connection was vertical. Changing it to horizontal and doing the right modelling nozzle loads dropped substantially.

In the tank case, the bulging of the nozzle create rotation of the nozzle so double gimbal or universal with 2 horizontal tie-rod can absorb this along with the lateral displacement from settlement.
An EJ placed perpendicular to the nozzle will be subject to torsion due to bulging so in my opinion is not very good.
In any case try to model the nozzle with flexibilities.

If bulging is not a problem, maybe a support tied with the tank foundation would be acceptable.

Regards