Hy Collegues,

I am trying to model a pressure balanced Expansion joint but in my opinion it does not work in the right way and I don't understand the reason:

the model is schematized in the following site:
http://www.ejsus.com/ejssearch/ejs.htm?m...1&action=search

does anybody has and example to send by mail? Soon I'll post images of the modelling for comments. Another question is related to the thrust force when we use ope bellows on pump; when I check the load on Nozzle, I find the contribution of the thrust force on pump flange: is it correct or this contribution act on the body of the flange?

Many thanx for you help!

Hy,

here is the scheme I have used to model the exp joint: the image is related only to half part, the second half is specular and the restraints are the same working to the other rigid tie rod.

http://i.imgur.com/PqBc6b6.png?1

When modeling an in-line pressure balanced expansion joint (ILPB) I recommend using a much simpler model, that being a single zero length bellows and:

1) Single zero length bellows with the overall spring rate of the three bellows.
2) Center the bellows in the length of the joint.
3) Model weld ends on either side of the bellows equal to ½ the length of the joint.
4) The weld ends should be set to ambient temperature.
5) The weld ends should be rigid elements with the weight set to ½ of the total joint weight.

It is possible to develop a detailed model of all of the bellows and restraints but it’s not worth the time and the possibility of making a mistake is high. The above simple model will accurately simulate the expansion joint to the system. The axial movement will have to be manually increased for the length of the joint.

Hi Lorenzo,

In my understanding, the thrust force which Ceasr is showing on pump nozzle, that will be transferred to pump foundation through casing. It will not act at pump nozzle.

In the past, I have followed these guides from Senior Flexonics:

Modeling In-Line Pressure Balance Exp Jts

In-Line Pressure Balanced Exp Jt Spring Rate and Movement Calcs

Modeling Metallic Bellows in Pipe Stress Programs

Hi,
I have some doubts on how to model In-line Pressure balanced expansion joint specially on restraints (rotations allowed?)
Here is a scheme of the expansion joint.
Could you comment the model.

Thank you

Nicolas61 - Looking at your model, I see that you have used the detailed model procedure. I still recommend the simplified model discussed above. You should also download and read the information that Mamacint provided.

Hi Dan,
Thanks for your reply.
I had modeled ILPB detailed before reading this post. I'm gonna compare both models.
But is there something wrong on my model.
Thank you

Nicolas

Nicolas61 - The principal of this forum is to respond to general questions on practices and procedures. Specific requests for review and approval are too time consuming and potentially error pron and therefore are denied.