Dear Stress Analyst,

I am modelling universal expansion joint using the expansion joint modeller. We had bad results, we had failure in code compliance and very big nozzle loads. What I did is I made many trials, I put 15mm gap in the tie rod, I use very small stiffness,making my expansion joint almost free and flexible. I had the vendor's data for expansion joint but I did not follow the data like stiffnesses . My point is I will inform the vendor for the results what I had obtained and they can design again an expansion joint that can be suitable for my piping system. My question is. Is it possible for them to design an expansion joint by giving only the displacement in end to end (flange face) in expansion joint? What must I do?I need your help guys.


Regards,
Machoguy

The problem is most likely pressure thrust. Send in the job to techsupport@coade.com and I will take a look. It may be that something is entered incorrectly.

If you have gaps between the nuts and attachments then the rods are not control rods. Rods with gaps are limit rods (And you do not have true universal compensator). Loose rods are used to limit damage if your anchor/s fail. This type of compensator will alway have full pressure thrust. You will have large nozzle loads.

Before you continue you need to figure out:
- do you need a compensator
- is the selected type correct compensator type

My bet is that you have incorrect type/arrangement. Check 3 hinge compensators in 3 pin system. May solve your problems if you have axial and lateral movement.

To answer your original question. Compensator designer requires a lot of info to design any compensator correctly. There are only few companies, which try to give full details. Typical list includes movements, , pipe dims, pressure, temperature, external loads, space limitations, material limitations, what is inside, what is outside, flow conditions, cycle requirements, pipe design code, bellows design code, pressure test requirements, NDT requirements, marking, packing, installation position...

Hi Good day to all of you.

I want to clarify about my universal expansion joint vendor's data. The vendor give me design movement conditions like axial, lateral and angular.
My question is how to use these data? Why they have axial movement condition since universal expansion joint cannot accept axial movement? Please I need your explanation although I can ask directly to my senoir's advice but I like to post my question here.


Regards,
Machoguy

Talk to the vendor.

My guess is that these data are for the individual xj's and not for the tied xj assembly.

If you read Sam Kannapan book in Chapter Exp. Joint & Exp. Loop, there is statement to limit lateral movement and such moments on bellow for such exp. joint. When you make the model, observe what part of exp. joint at each built element. At the output observe reaction & displacement there. Take a close discuss w/ your vendor for the allowable Moment & Displacement.

I would say you do need to talk to Pathway. The design is for a unit that has specified axial movement. Bellows designer has to consider nipple (Item 4) and pipe end expansions as they are inside the rod flanges. However the given movement is too big for this. In addition it seems that it is axial extension and not compression (Based on calculation). There is a small possibility that the designer is considering presetting and has used the software extension for this purpose. Drawing shows it as compression.

Please note that the rods are called "limit rods". This is not universal design. In general it is not a standard design.

Thanks for the calculation. I like always to check and compare other design calcs to my own software.

I get the same results for the design. They are giving you working spring rates and not initial elastic. They have their own fatigue material data, which is allowed.