Dear All, I have some questions:
1)I don't well understand what the pressure thrust caused by expansion joint is. Can anyone explain to me it?

I ask it because I need to model a expansion joint in my piping system. I set the axial and lateral stiffnesses as per manufacturer's catalog but I don't have any information about "Effective ID". Then the second question is:

2) Is it mandatory to consider the "Effective ID" parameter?
Do I make a serious mistake if I omit this parameter?

Thank you to all.

Dear Aleps,

I’ve attached a bulletin which explains pressure thrust as it relates to expansion joints. Regarding your questions:

1) The “Effective ID” in CAESAR II is actually the mean diameter (IDmean) . Most manufacturers catalogs provide the effective area (Aeff), so you can calculate the mean diameter via: IDmean = (Aeff x 4 / Pi )^.5

2) The pressure thrust is extremely important as the attached bulletin indicates. Omitting it could expose your system to extremely large axial loads that your analysis would not include.

Dan Edgar

Dear Edgar,

Thank you for your response but in my manufacturers catalogs the effective area is not provided, then, you can suggest me a typical standard effective area for 8" simple bellow expansion joint?
Thank you.

Furthermore, I'd like to highlight that in my piping system there isn't a real expansion joint but there's a adaptor couplings in order to connecting pipes of different outside diameters ( see the link http://www.flexseal.co.uk/products/flexible-couplings/adaptor-couplings/#.U_XNO6NmMVY).

Initially I modelled it as a simple reduction 8"x6" but the client does not agree and they want model this device.then, How can I model the adaptor couplings?

Dear Aleps,

I checked the website you provided. It's for a rubber reducer utilizing pipe clamps. As such, it is not really an expansion joint. It's a devise for reducing the diameter on very low pressure systems that has some movement capability. As such, the pressure thrust will be different on either side of the joint. It will be 6" on one side and 8" on the other. CAESAR II can not model this and you'll have to input 0 for the Effective ID but then apply a force equal to the pressure thrust at the joint center line.

Dear Edgar,
According to you, if I want consider the adaptor couplings in my model:
- I have to model an expansion joint, I leave blank the Effective ID field, but which stiffnesses Can I consider?

Regarding the pressure thrust, It is present at the moment that I insert a flexible expansion joint but in this case i'm not sure that this force is present.The pipe remains rigid, this device permits the change of diameter and it avoids leakage of fluid. Please, correct me if I am wronging.

Conservatively, Is it not correct to consider a simple 8"x 6" reduction in the model?

The problem is that, if I consider a 8"x6" reduction, I'm considering a 6" pipe welded to 8" pipe and it will result high loads at nozzle connection.

Really the 6" pipe is connected to 8" by adaptor couplings (as described above), therefore the 6" pipe won't be welded to 8" pipe.

But, Can I consider it in my Caesar model in order to reduce the loads at nozzle?

What pressure is your line?

The design pressure is 2 bar.