I have one doubt about using Tied Expansion Bellows.

Actually Now I am doing Hot water Pressurized Line. According to Vendor document I chose convolutions and axial rate of Bellows and all details. But now my Engineer does not satisfy the Output results of Bellows. So we decide to change the vendor, he suggested only 6 convolutions and give different axial rate. How can I change all the details for my CAESAR MODEL?

Can I simply replace all the values instead of Previous Values?
(I attached the Image)

Is it correct?

If i am thinking wrong Please Correct me?

Hi priyan

if you use tied expansion bellow then effect of axial stiffness will vanish.
Tied bellow arrest axial flexibility of bellow.
In case you use vendor data from different just change input data as you have already done.
When vendor is giving stiffness data then number of bellow convolution as no importance to you.

Yes i consider your advice. But In my attachments i am choosing 10 convolutions it gives Axial Stiff is 3179.973. If i am choosing 6 convolutions it gives 9280.606.

so whenever we increase convolution length our axial stiff the value is decreasing. Not Vanishing.

Is it Correct?


I do not know why this much difference in Axial Stiff.

Not only Axial Stiff, Torsion stiff is also give much difference value.(See the attachment)

If i am thinking wrong Please correct me.

HI shr
if you use tied expansion bellow then effect of axial stiffness will vanish!

if you do the complex model about the EXP,you should need the axial stiffness ,and in some cases,it can absorb the deformation of the pipe between the two bellows ,and can check the force and moment of the ties.

but about the simple model of the draw- bar lateral expansion jonit,the EXP length is 1200mm,can you ever model the zero length ?i always model the 1200mm length,but about the 1200mm length model,if the the EXP weight is large,maybe the EXP weight distribute maybe isn't equal for the pipe system?what do you think it?

regards
zzw

Hi Priyan
Effect of axial stiffness vanishing means it is not out from input data rather it's overall effect vanish from system.

In simple way to understand bellow is very similar like spring.
Now if you increase length of spring (for same type) it's stiffness property will decrease, similarly if you increase number of convolution of bellow it's stiffness will decrease.

Now concept of tied bellow is similar to two spring in parallel.
effective stiffness K=(K1+K2), where K1 & K2 individual stiffness of springs.
Compare with tied bellow , overall stiffness equal to stiffness of rod + Stiffness of bellow.
Now axial stiffness of rod very high ( depends on diameter of rod )

when stiffness of bellow change a little overall axial stiffness of tied bellow do not change much since rod stiffness is very huge & deciding factor.

Hi zzw
your point is not very clear to me.
Anyway tied expansion bellow is not design to absorbed axial expansion, either you make simple model or complex model.
Length of tied bellow you mention 1200mm is slightly high. Please check vendor catalogue.

Extraordinary explanation shr.

thanks for your valuable information.

HI shr

in the space 'Z' pipe,you can use the tied expansion bellow ,because it can absorb the axial deformation of the pipe between the two bellows ,except the absorbing the deformation of the lateral direction,in the case the pipe is long between the two bellows

Length of tied bellow you mention 1200mm is slightly high. it is not high,i have do more long The tied expansion bellow

Hi zzw

Are you intend to use two tied bellows or one tied bellow in Z shape piping configuration ?

If you want one bellow I guess you like to put it in middle leg of piping.
If you want 2 bellows you may use it both end leg of piping I guess in that case your middle leg is quite long.

Whatever case may be your tied bellow absorbed lateral deflection only , not the axial deflection. May be absorbing lateral deflection it fulfill your purpose, I mean reduce nozzle load.

HI shr
generally ,there is one the draw- bar lateral expansion in Z shape piping configuration ,maybe i can't explain cleariy the EXP ,i am so sorry,
i mension the draw- bar lateral expansion jonit ,please to see the picture

Hi zzw
Yes this kind of 2 bellow unit used to absorbed more lateral expansion than a single tied bellow.
In this case also it arrest axial flexibility.
You can get better nozzle load by using this kind of bellow.

HI shr
do you have simulate the cpmplex the model of the straight pipe pressure-balanced expasion jiont?

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