I am new for tied bellow design so kindly advice me how to create the tied expansion bellow and what are the stiffness values to be filled in the CAESAR II expansion bellow design dialog box (axial stif, trans stif, bending stif, torsional stif and effective id).
I have studied books but I am not get clear idea about tied expansion bellows, mainly I have conflict on tied bellow restraints.
I modeled 24 inch pipe dia, 200 meters long (straight pipe), temp @ 46 degree C, pressure @ 16 bar, corban steel pipe for chilled water piping application.

A EJ-1 B EJ-2 C
X-------''''--------X--------'''''-------X

Starting, mid and end points are consider as a anchor, here I used tied bellows (EJ-1 & EJ-2) between two anchors.

I modeled the flange, bellow and tie rods, The pipe axis is X, so I provide X, Ry and Rz restraints at one end of the tie rod, the other end no restraint support.
Finally I run the analysis the anchor loads are around 130 tons, I thought that I made a mistake in this analysis.

Kindly advice me how to reduce the anchor loads.

1. Additional bellows are required to reduce the anchor load.

2. If can I provide gap at X restraints or only one side restraints like -X or +X,
Here the One side restraints also more anchor loads.

You are using the wrong type of expansion joint. Tied Universal expansion joints will only absorb movements perpendicular to the EJ axis. You are attempting to put them in line. With straight pipe you only have the option of using an unrestrained expansion joint (X-Press) which will expose your anchors to the system pressure thrust ( Pt = P x A) or an in-line pressure balanced joint which is very expensive. I’d recommend you download our EJ catalog from myej.com and review the discussion on expansion joint selection.

here i have to use the expansion join without tie rod, this is right way to proceed the stress analysis and kindly advice what are the stiffness values to be filled in the CAESAR II expansion bellow design dialog box (axial stif, trans stif, bending stif, torsional stif and effective id)

regards
rajiv

The values depend on the movements to be absorbed by the joints. Make a run, calculate the movements to be absorbed and then go to the catalog for X-Press style joints and select the joint that is capable of those movements. You will then find the axial stiffness in the catalog. The lateral and angular values will be rigid due to the self-guiding feature of the X-Press.

Thank you very much for your advice, and i discussed with my client, they are asking me to design the bellow with tieds, kindly advice me, if we have any bellow with tie rods for above straight line pipe and why we can not use the tied bellow in straight line pipe,
I seen one tied bellow, the tie rod each ends we have nuts on outside of the bellow flange but not in inside. So no restrictions during the axial compression (towards inside) and also it try to move axial expansion (towards outside), here I put the bellow between two anchors so only compression, only the tie rods are used for extra safety during the axial expansion. can we use these kind of tied bellow.

Please find attached bellow image for your view.

kindly advice me.

Regards
Rajiv

The rods you are discussing are LIMIT RODS and are a safety device designed to engage only in the event of a main anchor failure. They will have no impact on your model and should not be included. Here again, they are discussed in our catalog that I recommended that you download.

Hi Dan, good day.

With regards to axial expansion joint, is it correct that there should be a thermal force greater than pressure thrust before the expansion joint starts to compress itself?

And also for tied expansion joint, adding a gap in the inner nuts of tie-rod to allow compression would require a thermal force equivalent or greater than pressure thrust. Is this correct?

Thank you.

In the “normal” axial compression configuration, X-----|||------X, the pressure thrust will develop at the elbows and then be resisted by the thrust anchors (X) and the only load in the pipe line would be the thermal movement times the axial spring rate of the expansion joint (|||). Since the pressure thrust is being eliminated at it’s source, the elbows, the pipe will no longer be in tension but slightly compressive. As a result, the line will need to be guided as though it was a compressive column. See the guiding requirements discussion in our catalog.

Thanks for your answer about the untied axial expansion joint. The two anchors will be the ones subjected to pressure thrust load.

How about for tied-expansion joint with gap in the inner nuts? I thought by adding any gap will introduce pressure thrust again in the system because EJ can be in tension/compression again, and will defeat the purpose of tie-rod. Is it correct?

Thank you.

See my comment on 1/10/14. When the joint compresses, ie inner nut gap, the pressure thrust will develop at the main thrust anchors at the ends. The rods should than be referred to as "Limit Rods" and will not effect your model and can be omitted. Limit rods will activate in the event of a main anchor failure only and are a safety feature.

thank you sir