Dear All,

Please suggest me for 1626mm OD pipe how can I put the data for Hinged Expansion joint.
For that Expansion joint can I get the data from EJ modeler. If not , then please help, how to do?

Also pls help me how to attach that same Arrangement drawing, so that you can better to understand.



Thanks & regards
Gyana

Hi Gyana
Modelling procedure is same irrespective of pipe diameter.Check user/application guide for modelling.
For large diameter pipe you have to ask vendor for bellow property you can not go for caesar default modeller.

If you want to attach file here, while replying you are getting option
" Reply Quote Quick Reply Quick Quote Notify Email Post "

Go for Reply there will be option for "File manager" , you go there & can attach file.


Regards

Habib

When modelling the compensator do not forget the mass of the hinge arrangement. It can be quite a lot. Hinge forces can be high. With these large sizes you should consult a bellows designer if you have no experience with them.

Hi,

Thanks for early reply.As suggested by you I am attaching
that file please look.Again very very thanks.





Thanks & Regards
Gyana

Sorry but I absolutely and totally cannot understand what you try to do with these hinge compensators if positioned as shown. If they are rotated 90 degrees then I may understand. If rotated you may need a third in the long leg. Instead of two spring supports you may be better off with a guide.

Do you have a wind load on this?

Not so often here. If question drop an e mail/priv message also.

Dear Jouko,

I am really very sorry for late.

1. Actually on that attachment drawing the positions as shown is wrong.
Yes these are now rotated to 90 degrees.

2. No there is no wind load.But i want to know, if this have a wind load
on this then what to do?

3. As suggested by When modelling the compensator do not forget the
mass of the hinge arrangement. It can be quite a lot. Hinge
forces can be high.

So what we should do, if we know the mass of the hinge arrangement.
Which value we should put? As i know there is no options to put the
Expansion joint weight.

Kindly guide me ASAP.

Thanks & Regards
Gyana

Hi Gyana
At one end of pipe you mention fixed support , other end I guess a nozzle.
Since temperature is quite high attached bellow location is simply not going to work.
Are you doing a revamp job or copied data from old plant to build a new one?
For hinged bellow, weight of hinge is quite high. At the time of hinge rod modeling Put weight of hinge ( where Caesar default put zero).
Wrong bellow type selection & wrong location of bellow may cause more harm than good in system.
You may pass all relevant data/information to my personal Id. I can try to help.
My Id habibur21@gmail.com

Regards
Habib

As said not often lately here. Very late answer.

If you have wind load you have to include it. Bellows designer has to know all the forces, moments and directions. Also if pressure thrust is included or excluded plus statement if the forces are on centre line or somewhere else... I have done quite a few bellows designs. About the only time I have received correct design data was when I received CAESAR II model from the stress engineer. We worked together to get the model correct.

Hi Jouko

**Also if pressure thrust is included or excluded plus statement if the forces are on centre line or somewhere else**

Can you please elaborate the above statement.

1) In which situation we may expect forces at off centre? Can we observe that in caesar model?

2) pressure thrust is included or excluded --Do you mean that sometime we may not consider pressure thrust in CAESAR for bellow considering the same will be taken care of Tie-rod /Hinge/Gimble, & subsequently our output result also change a little bit.We need to inform bellow designer about our pressure thrust consideration in caesar.


Thanks & Regards

Habib

Normal calculation results from CAESAR II are on the centre line but if you build fancy model you may get forces and moments at the hinge points. Bellows designer has to know what you give to him. Think of a torsion moment as an example. If you give the moment at the centre line the designer has to do some calculations. Moment can be carried over the bellows via the element or hinges or both. All depends on stiffnesses. To calculate the hinge pin and bracket the torsion moment in the centre line is "converted" to two forces 90 degree to the pipe centre line. On the other hand you may give some forces at the hinge pins and then the calculation would be different.

When you give the forces and moments you need to specify what is included. One item is the pressure thrust. Some engineers leave the pressure thrust out if the bellows design is such that the force is carried by the hinges or rods. If you do not tell the bellows designer that the pressure thrust is included he will most probably add it again and then the design becomes too heavy. Other items to give are what bellows mass was considered and if there are any additional forces or moments the designer should consider (additional axial force during hydro testing or similar).

Pressure thrust issue becomes easily problematic. For instance if you have sliding supports CAESAR II may calculate smaller than pressure thrust as axial force at the bellows. In such case bellows designer has to consider the full pressure thrust instead of the calculated lower calculated value. An other potential problem area is if the pipe is installed vertical. Mass of the pipe can work against or same direction to the pressure thrust. Bellows designer has to know the highest force, which may not be during operation. Worst case can be when pressure is lost but pipe is still hot.

Now. If somebody reading above decides that it is best to include some extra safety marging into the forces and moments to be given to bellows designer then that decision is the worst decision that can be done. Additional safety marging can easily result in bellows that doesn't work.

Bellows design is not an easy business. Most of the time it is made more difficult by the stress engineers.

Hi Jouko

Thank you very much for your explanation.
Your post is really informative & interesting.
I was under the impression that since we specify calculated load & pressure in the line so bellow designer by default to follow supplied load data or pressure thrust whichever is higher.
Specifying pressure thrust consideration in caesar or not could avoid over design of bellow.

You additionally mention “Additional safety margin can easily result in bellows that doesn't work”

Do you mean additional load may require more hardware requirement hence increase bellow weight. That might create another issue in piping system.
Because even at higher force & moment design also I believe bellow designer should follow same specified stiffness property & effective ID.

Thanks Again

Habib

When you increase forces and moments they mainly result in heavier rods, brackets gimbal rings and similar. Increasing torsion moment may require thicker bellows element increasing the spring rates. Any increased force and moment on brackets can be problematic. Typically brackets are attached to thin pipe ends. Forces and moments result in deformation and very high local stresses. Solutions are to make thicker pipe ends, longer brackets, reinforcing pads or rings... All add mass, cost money and cause all kind of problems including high thermal stresses during start up and shut down, sometimes even during operation.

If your design has some NB200 bellows in normal process line the problems are minimal but if you have high temperature or pressure or diameter or combination of these then there is a problem. To get correct solution requires close co-operation between the stress engineer and bellows designer. And both have to be competent on their field. Plants are full of failed and wrongly designed bellows. It is surprising how many of them actually don't blow up or damage other equipment.

I could give more detailed explanation of the decision making and design process but this is a bit wrong forum and the space is limited. Last detailed presentation I made on this topic contains one bellows design over 60 pages and other documentation a bit more.

Hi Jouko

Thank you very much for your explanation.

Regards

Habib