Hi experts,

I am working on a Regenerator internal SCSP pipe connected to SCO well & found that there is slip joint near to aeration nozzle.

Just want to know below:
1) What exactly is slip joint & how do it differ with other kind of bellows?
2) how to model slip joint in caesar ii?
3) what stiffness needs to be considered preliminary if vendor data is not available?

1) A slip joint comes in single or double slip joint configuration. The pipe is allowed to telescope with pipe-in-pipe design. Double slip joints are anchored in the center.

2) As an expansion joint, or 2 expansion joints on either side of an anchor.

3) In reality, as it's pipe in pipe, you would expect a lateral stiffness equal to that of pipe when extended, and double that when collapsed. CAESAR doesn't understand that, though, so you should use a stiffness that makes sense. Zero axial stiffness for static analysis.

Thanks Michael for your response.

However, i am not clear on your below point:

1) "a lateral stiffness equal to that of pipe when extended, and double that when collapsed".
2) "Zero axial stiffness for static analysis"

Can you pls elaborate further on above 2 points in regards to slip joint

Thanks

1) When fully collapsed, it is a pipe inside a pipe. When fully extended, it's no longer really a pipe within a pipe. Therefore, it'll be approximately double stiffness or single stiffness, depending on which configuration the slip joint sees. To that end, there's not really a good way to demonstrate a variable stiffness of an expansion joint in CAESAR, in this manner. So, pick one that's conservative.

2) We use the (corrugated) expansion joint in caesar because both will see pressure thrust, and lateral stiffness.

When a corrugated expansion joint is compressed externally (let's say, by an operator driving a forklift blindfolded), it will resist the load in increasing amounts due to its axial stiffness, and then, if the external load is removed, the corrugated expansion joint will push back to its uncompressed form.

For a slip joint, while friction will resist the forklift, the slip joint will not go back to its original shape when you release it.

When we say zero stiffness, that does mean if we calculated forces for the forklift scenario, that zero transmission at the slip joint anchor will be reported by CAESAR. This is, obviously, incorrect, but also beyond the scope of CAESAR. I would suggest looking at the loads on adjacent supports if you're required to design the slip joint anchor.

I think you can reasonably find the axial displacement with a start model (the value would be not so sensitive to the lateral stiffness) and try to adjust the lateral stiffness by input the result of a hand calculation valid for that position of the telescopic assembly. In any case you can try few iterations if really necessary.