RIGID WEIGHT OF VICTAULIC COUPLING

Friends,

Though a lot many discussions have happened over a period of time regarding "How to model a victaulic coupling" in caesar.
I read the article by Mr. Dave Diehl, in Mechanical Engineering News June 1998 edition, where he explained modelling a victaulic using Node/CNode with restraints.




I got a doubt on how to add the weight of the coupling as Rigid at that particular node location as no separate pipe element is created as per that method.

Thanks in advance for providing your views and taking out time.

Regards

Instead of two pipes CNODED together, have two pipes, two rigid elements, where the two rigid elements are half as long and half as heavy as the coupling, and have the two rigid elements CNODED.

Michael,

Thanks for your reply.

I want to know whether that coupling length to be used (2 half lengths with two equal half weights) is the coupling thickness or the pipe gap, i.e 10 or 15 mm gap b/w the pipes which is required to take up the thermal expansion?

Regards

Total Installed length = Total CAESAR length.

Hi Check this log back our lead stress Engineer Steve from London done some study on this couplings. May be use fully for you.

Points to be take care

1.span to follow as per vendor span chart.
2.Check the Hydro test pressure its with stand or not.
3.which type of coupling you are using like some flexible coupling then model in Caesar. Rigid coupling not required to model.
4.Are you using for any big bore cooling water lines...
check the spans if support span not meeting change to welded elbows....

regards

akula

Further to the above post, attached are some guidelines for modeling of flexible and rigid Victaulic couplings,
updated and corrected in 2012.
Hope useful.

Dear Steve,

Thanks for providing your valuable thoughts on the matter and providing the reference file.

The figures in the PDF are not visible; can you please send the file again with figures visible in the same.


Regards
MJ

Michael,

I tried with the method you explained to put rigid weight for the VC along with restraints as explained by Dave in the article as mentioned in thread.

While running the pipe for static analysis, sometimes Caesar couldn't find a solution and runs iteratively. Upon checking (by pressing F2), it shows "old state close, new state open" for few nodes where VC is installed.

Can you please explain why am I getting this kind of error in my file. The error doesn't appear for all the nodes where VC is installed.

Thanks & regards

MJ

The why is that CAESAR runs several numerical simulations on the model in order to error-check itself, and that the method in question is resulting in a non-linear support switching between "in use" and not "in use." E.G. in odd-numbered calculations, CAESAR thinks a given support is sliding or hitting a guide (or whatever non-linear condition), and in even-numbered calculations, CAESAR thinks the same support isn't slighting or hitting a guide (or whatever non-linear condition).

The strange part is that this can be caused by a number of non-linear supports elsewhere in the model culminating and centralizing here.

Verify that your VC CNODE supports make sense, and aren't too elaborate. Then look at other supports in the model, particularly near your VC. If any are lifting off (or are trying to), you can adjust the friction value (or removing it).

If you still can't get it, try posting a screenshot.