Dear all,
I´m a new user of Caesar II. I need to model a DRESSER Joint (it´s not a comum expansion joint)and I hope you can help me.
I found at CaesarII's tutorial a explain about "Slip Joint" (similar to DRESSER JOINT). I have dificult to define the stiffness K1.
Another question is how to permit the angular moviment?
Best regards.

Maybe you can create a few different models (using File->Save As and change the name) with different values of K1 so that you envelope it. That way you can determine how critical selecting the correct value of K1 is on your results throughout the model. If it becomes important you will have to contact the manufacturer and hope they can give you some guidance.

If you modeled this as a zero-length expansion joint then use a small value for bending stiffness. Then input a Z2 restraint with K1 set to some large value and K2 set very small (it must be greater or equal to 1.0), with Fy being your break-away torque (ft-lb, not lb). Then input the angular restraint (Rx, Ry, or Rz as appropriate) with a gap equal to that allowed by the coupling.

I looked into this coupling. There are similarities between this and Viking Johnson coupling. I have a technical paper I have writen on VJ coupling modelling. I try to attach it to this message. If it doesn't work please send me your e mail.

Thank you!
I finaly modeled joint type dresser. The VJ coupling are very similar.
About the techinical paper, I have a doubt. What is the influence of the legth on the results? I did some tests with differents legths (50mm, 100, 300mm) and the results are almost the same.
Please, do you can imagine why the author suggested 10mm?

Regards,

NaOliveira

I wrote the paper.

Originally the length was 10 mm because the rubber ring is about that length. The development was quite long. I had really horrible results in some calculation cases. Plant owner's specialist originally insisted defined length. I used the one that gave the best result. I made several units and for the last 2 I used zero length.

Sorry! I forgot that you wrote the paper!
In my case, the axial moviment is around 10mm / 20mm. I cannot consider a zero-legth with high axial stiffness.
I used high translational stiffness and high torsional stiffness. The axial and bending stiffness I used like indicated in the paper.
I did some tests and it seems to be ok. I were afraid of the legth, but maybe it´s right.

Do you have more papers in reference to modeling with CaeserII?

Thank you very much!!!!!!!!!!!!!
Best regards,
Naoliveira

I think you may be destroying the coupling. Make sure that you read the suppliers documentation. Viking and Johnson coupling has a rubber seal. Maximum axial movement allowed is the deformation of the rubber. If the seal slips on the pipe it is destroyed. If this dresser type is a slip joint then the situation is different. In both cases you need to take care of the pressure thrust. You cannot rely on the friction between the seal and pipe. Also you need anchors quite often to make sure the couplings do not slip out. VJ has good literature. I have not studied DRESSER.

Each coupling type has its own limitations and good points. Often they are misused. Read the documentation!

You can look on my site www.jat.co.za. There is some software to use if you use stress ISO.

naoliveira
Please can you share modeled dresser joint CAESAR II ?