Hello everyone,

would you please tell me how do we define a flexible victaulic joint? Only with gaps? And how much are the maximum gaps in axial and angular directions which I can use? The attached system is what I'm trying to model.

Thank you

This may help

Thanks Faizal, according to this article I can model it with Node/CNode restraints with gaps. But I found some cases in this forum that have modeled it with an expansion joint in the middle. I want to know if I hve to do the same or modelling only restraints with axial or angular gaps would be enough?

Thanks

I would suggest to model an expansion joint (with almost zero length) to include the pressure thrust in the piping. Mr. Diehl suggested to add Pressure thrust manually in the Caesar model, as a better option to model the Victaulic coupling.

Regards

Thank you Nidh

Another question is how I can see the effect of pressure thrust added manually or by expansion joint in the expansion case? normally pressure thrust is not included in expansion case and I can't add the added load F to expansion load case. I mean how would my load cases be to use the extra gap due to pressure thrust?

regards

There is a Configuration Directive to include pressure variations in the Expansion load cases. Note that pressure variations are not the same thing as the pressure thrust caused by expansion joints. Pressure thrust loads are included when Px is included in the load case. Pressure variations are included in a range (Lx - Ly) evaluation.

Charlot,

If you model your pressure thrust as a force in CAESAR II, you will have to add that load group (e.g., F1) to the load cases by hand. By default, CAESAR II does not consider these force sets as part of the sustained or expansion loads.

If you specify an effective ID for an expansion joint, CAESAR II will automatically include the calculated P*(effective area) on either end of the joint in load cases that include pressure.

Thank you Dave and Richard,

So what I understand is that adding that expansion joint and related pressure thrust load don't help my expansion case.
That extra gap due to pressure thrust is used in load cases that include pressure. right?

Regards,

I was answering a CAESAR II question.
I've seen assemblies of several Victaulic coupling one after the next. So arranged, these assemblies provide lateral flexibility. The pressure thrust will also pull these couplings away from each other and limit the flexibility they provide in the axial direction.
If you use an untied expansion joint or a series of, perhaps squirmy, Victaulic couplings you must provide some sort of pipe support to control axial pressure thrust. Usually, one side is anchored and the other side is highly guided and running direct to a nozzle.

You may not be required to investigate pressure thrust but you better accommodate it - for expansion joints either with hardware around the joint (tie rods or hinges) or added pipe restraint.

Going back to your original attachment - you show assemblies of Victaulic couplings that add system flexibility by twisting at the couplings. These are flexible Victaulic couplings. This is not the axial flexibility I was addressing above. These assemblies act like linkages rather than beams in bending. The stiffness method employed by pipe stress programs does not provide this sort of response. The stiffness method establishes straight line response, not arcs of response. You design the assembly with sufficient clearance so that twist can occur freely without binding the overall assembly. It's kind of like flexible metallic hose - you install a hose long enough to accept the required displacement rather than evaluate strength of the hose if it is too short. I believe you will find that the Victaulic people would use CAESAR II to evaluate load on their rigid couplings but simply assure clearance on their flexible couplings.

Thanks a lot Dave,

Sorry I mixed up different issues. But your answer was complete.