EXPANSION BELLOW STIFFNESS ADJUSTMENT-REGARDING

DEAR ALL
I NEED TO PUT AN EXPANSION BELLOW ON THE EXISTING STEAM LINE, SO THEY GAVE SOME LOCATIONS IN A STRAIGHT PIPE.WHILE ADDING A EXPANSION BELLOW IN THE LOCATION I HAVE 20 TON LOAD ON ANCHOR, SO IF I REDUCE AXIAL STIFFNESS VALUES AGAINST THE SOFTWARE VALUES ,I GET 10 TON LOAD ON ANCHOR,IS THIS METHOD IS CORRECT AND I CAN GIVE THE CHANGED STIFFNESS VALUE TO SUPPLIER,PLEASE ANY ONE GUIDE ME
REGARDS
RAMESH

Dear Ramesh

Why you are trying to use expansion bellow in an existing system?
Does the system already had bellow & you want to replace with new one?
If so follow the datasheet of the old one. Check type of bellow ( Tied/ universal).
I guess you model untied expansion bellow & trying to manipulate by changing it's stiffness. Note that it will be worse in case you put wrong bellow in wrong location. Study carefully before make any decision.

Regards

Habib

Good grief, get some expert help.

Hi Habib,
thanks for your reply
i want to analysis for a steam line of 170m straight pipe with 180 deg c with 14 bar pressure.one end is fixed which comes from engine room other end is allowed to move 330mm as per expansion. but now what is the problem is site not required the expansion of 330mm and they have only one flanged spool in mid of line.so they want to introduce a bellow over there.We want to put a new bellow.first i tried with untied bellow and i get a anchor point load of 20 tons. for reducing anchor point load i reduce the axial stiffness value.is this is correct method.
regards
Ramesh G

Dear Ramesh

It's not very clear why previously there was no problem now you want to change. You can look for possible route change.
provide some sketch with explanation.

Regards

Habib

Hi Habib,
problem is movement over 330mm, support not designed as per stress analysis,now pipe shoe came out of supporting member.so in last 8 supports full shoe came out of beam and pipe sitting directly in beam.then remaining supports moved corresponding to thermal expansion and sits in beam.so site people says in mid of line(170m) they have some break flange so they can introduce a bellow over there.based on the movement some other piping also fouls with respect to the main line branches.
so now they want to put a bellow and want to avoid movement from 330 to 150mm.so only i am analyzing with bellow,but for me anchor point load come nearly 20ton to reduce i adjusted the axial stiffness is this method is correct.
main consideration is avoiding hot work.but they gave some limit to do hot work not much.

Dear Ramesh

Unfortunately bellow should not be considered as possible solution in this type of cases. You can not avoid hot work anyway.
1)Use long length shoe
2) Addition elbow
3)Re route the system.

Using bellow you may end up with another mesh up.
Good Luck

Habib

Provide 3d loop in the existing system and as per experts advice avoid the use of expansion joints.

Dear All,
use of expansion loop is not possible,here condition is we should not do hot work.pipe is in pipe rack.we have one break flange in mid line, so site people wants to use bellow in the existing spool.plant is in running condition so avoiding hot work.management wants as per operations manager decision to use bellow but every one wants engineering clearance.so all waiting for me to provide report with one expansion bellow.but my problem is using expansion bellow i have a 10 ton anchor load axially.if i reduce axial stiffness i get reduce load in anchor point.please advice me is it correct method.
regards
Ramesh G

Dear Ramesh

Many people in the industry believe that bellow solve all the problem. But want somebody else to be responsible for that.
The method you are following is not correct.

In case your management want only bellow option, use IN-LINE PRESSURE BALANCE bellow if available space & cost permit.

Regards

Habib

Hi Habib,
How to model IN-LINE PRESSURE BALANCE bellow in CAESAR,can you advice me how to do this,and send a sample files what u have to rameshganesan.h@gmail.com.
really now iam in a difficult situation.
Regards
Ramesh G

Dear Ramesh

It has 3 part of bellow & two set of tie rod connected. Check vendor catalogue or ask for information from vendor. last time when I try to model this kind of bellow tie rod don't show good result in caesar, so I put effective ID of bellow as zero to remove pressure thrust effect, considering all pressure thrust will be taken care of tie rod combination of in line pressure balance bellow.
Note that this kind of bellow is highly costly & need longer space.

Regards

Habib

Dear Ramesh,

Please note that apart from cost and space, axial stiffness of pressure balanced expansion joint will be very high.Since in-line pressure balanced expansion joint consists of 3 inline bellows, axial stiffness of pressure balanced expansion joint will be very high as compared to axial untied expansion joint.

Regards,
KMF

Dear Khalid
we got approval to use 3 untied bellow in 170m straight pipe(steam line), by using 3 untied expansion bellow i get 18 ton load on limit stop near to 3rd bellow,how can we avoid this limit stop load, since the piping is analysed in pipe rack,every one is in trouble to solve this problem,its a thrust load ? how to manage this please advise.180 dec temp and 14 bar pressure.
Regards
Ramesh G

Dear Ramesh,
I read all the post what you had posted...and it seems a problem with the design. You can check for the pressure balance expansion joint......there is no problem with that......
Comming back to your original question of reducing the stiffness, I rem. I did this in one of our project where we dont have any scope for flexibility and need to reduce down the stiffness. In this case you need to check with the bellow manufacturer if he can accept or can give you an option of lesser stiff bellow....I remember that for me it took almost three months to finalized the bellow & lots of communication. So Best Of Luck

Regards,
R.K.

Dear R.K,
CAN U GIVE ME A IDEA OF MODELLING PRESSURE BALANCE EJ IN CAESAR.
CAN YOU SEND ME ANY MODEL FILES.MY ID IS rameshganesan.h@gmail.com.
please guide me how to use.
thanks/regards
Ramesh G

Dear Ramesh,
Unfortunately......I did not modelled them in Caesar-II...as per the client requirements we were forced to use the other analysis software. In that we modelled the expansion joint as a axial one and ignore the pressure thrust forces (it was having some seetings to ignore the forces in the load cases).
But I will suggest you to first get the tentative drawings & stifness for pressure balance exp joint. I will look in to the back up if i found anything i will revert on your personal mail ID.

Regards,
R.K.

Pressure thrust effects can not be adjusted by lowering the stiffness.

i know....but pressure balance expansion joint will balance the pressure thrust force and lower the effect on the support.....as well as the stresses.

Regards,
R.K.

True Dan...

Either you need to reduce pressure (which of course you can't) or use tie-rods for a lateral bellow!!!

No other way out...Although I figure out that you may avoid bellow in your case going through the whole story!!!Bellow on a 170m straight pipe seems a very odd case to me!!!

dear all,
WHEN PIPE IS VERTICAL – SUPPORT ARRANGEMENT IS X,Y,Z,RX & RY. RZ IS FREE TO ROTATE-REQUIREMENT TORSION ZERO.-ACHIEVED
WHEN PIPE IS IN 3 DIRECTIONAL SKEW- HOW TO ACHIEVE TORSION ZERO. FOR EG. PIPE X-10MM,Y10MM,Z-100MM.
Z IS VERTICAL.
regards
Ramesh G

Dear all,
i want to know whether CAESAR II Software can support wind and wave acting simultaneously.
We can give input details for wind and wave separately, but we want to run the case both acting together.
Regards
Ramesh G

Yes you can do this, just on the same element. Any give element can have either wind or wave, but not both.

You can have part of the model subjected to wave loading and part of the model subjected to wind loading - in the same load case.