Hi all,

I am trying to model correctly a pressure balanced expansion joint in CAESAR (with elbow, not in line). I thought that as they have more than two tie rods joining its ends, the bending stiffness should be very high (rigid).

Trying to know a bit more I have found a very interesting paper in the website of Pathway (http://www.pathwayb.com/Downloads/Manage...%20Programs.pdf), that includes table 1, according to which all angular movements (X,Y,Z) are possible for pressure balanced expansion joints.

But if both ends of the expanion joint are linked with more than two tie rods, I can't see how angular movements are allowed. Any suggestion or clarification?

Thank you for your help.

Please look any image for the expansion joint you describe. The rods go over two bellows elements and the centre piece is therefore "free". You may see some brackets between the rods and the elbow but they are not there to prevent angular movement.

This kind of bellows is quite nice design but can give grey hair to bellows designer. That balansing bellows together with long rods can be difficult to support. If you plan to use one, especially large size/high pressure please talk to reliable supplier.

please I am trying to model a pressure balanced expansion joint in CAESAR
with elbow, can you help me i didnt found any example
Thank you

Open a Support Request on eCustomer and ask for this model.

Hello Mr Richard Ay or Dave Diehl
I wanted to get this caesar file for pressure balanced EJ checked by caesar techincal guy because there is limited info on how to model pressure balanced EJ in your techncal guide. Please help or suggest someone who can help me !

Dear Sassimec,
It is the general policy of this blog that we do not review / approve specific pipe models. The blog is more for discussions regarding problems / bugs with the program and therefore the type of support you are requesting is beyond the scope of this blog. That’s the bad news, the good news is that since the model is almost entirely related expansion joints you can get assistance at Pathway’s blog at sfpathway.com under the ask the expert tab. Since I’ll be handling your request at Pathway, I’ll go ahead and send you my initial comments via a personal e-mail.
Dan Edgar, Pathway

Whoops! Sassimec, you have private messages blocked on your profile, so I won’t be able to respond to you. You can either submit your request at Pathway’s web blog or contact me directly via the e-mail address in my profile. Sorry for the delay.
Dan Edgar, Pathway

Thank you Dan Edgar for your quickly response , you can send me your comment by mail sessi.mohamed@hotmail.fr

the pressure at the balancing bellows elements (behind bend) must be zero,when i put this pressure, the restraint on the column and evaporator nozzles will be very hight value, when i change it to 3.5 bar, all restraint are ok, i don't understand this phenomenon. Please any advice or solution.

Mohamed,

I’ve tried numerous times to respond to your latest e-mail and it keeps being rejected. I’m not sure if it’s on my side or yours, so I’ll respond here.

I reviewed your model and it appears to be operating properly. Remember that CAESAR II will exaggerate the deflected scale to better visualize the deflected position of your model. Given this, I don’t see any problem. I check the bellows input data and it appears that all of the input is acceptable. The balancing bellows axial spring rate is approaching the minimum SR I’d recommend for this service and if your model can take it I’d recommend you make it the same as the line bellows.

Dan Edgar

Dear Mr. Sassimec,

Fine example(pressure elbow EJ.C 2)
I have the same problem at the moment with modeling a pressure balanced expansion joint in the elbow. Have you received an answer from Richard Ay or found what was the reason for your high forces with zero pressure in your file ? I would be very nice if you could help me.

Best Regards
Peter

Sir,

I went back and reviewed the discussion Sassimec and I had in 2007 and found that we resolved his comment. I have attached a discussion on modeling pressure balanced elbows (PBE) along with two example CAESAR II files. Hopefully this information will be of assistance, if not, let me know.

Dear Dan & Sassimec,

It is a great assistance indeed thank you very much! Please could you explain if really the trunnion behind th elbow gets the inner pressure, in other words is there an open connection between the elbow and the balancing expansion joint or do we have zero inner pressure in the trunnion ? These models show a shared pressure containment, this is correct ?

Best Regards
Peter

Sir,

Yes, we will drill holes in the elbow to allow the balancing bellows to pressurize. In this way, the longitudinal pressure thrust is moved from the elbow to the end of the balancing bellows.

Thanks sassimec.