Metal Expansion Joint
Metal Expansion Joint
(OP)
Hello.
It is my first time to design an expansion joint and I need some advice or tips regarding the design of expansion joint.
Actually, I need the parameters for Bellow Stiffness (for CAESAR II Input) and according to my research the vendor will provide those stiffness.
I was wondering on how the vendor will come out on such values for stiffness if the system in the CAESAR II did not yet run?
Do they have a pre-qualified selection/table? (The same like in the case of spring selection that the vendor will usually provide the table for selecting the spring based on the generated CAESAR II load of the pipe.)
In short, what data does the vendor needs to know upon requesting for the design of expansion joint?
Please help me to understand the process of designing an expansion for I have no experience on it.
Thank you and hope for your support.
Sincerely,
marchie
It is my first time to design an expansion joint and I need some advice or tips regarding the design of expansion joint.
Actually, I need the parameters for Bellow Stiffness (for CAESAR II Input) and according to my research the vendor will provide those stiffness.
I was wondering on how the vendor will come out on such values for stiffness if the system in the CAESAR II did not yet run?
Do they have a pre-qualified selection/table? (The same like in the case of spring selection that the vendor will usually provide the table for selecting the spring based on the generated CAESAR II load of the pipe.)
In short, what data does the vendor needs to know upon requesting for the design of expansion joint?
Please help me to understand the process of designing an expansion for I have no experience on it.
Thank you and hope for your support.
Sincerely,
marchie





RE: Metal Expansion Joint
Its been a few years since I have specified an expansion joint, but if you want to talk more in depth, PM me.
RE: Metal Expansion Joint
Thank you for your knowledge.
Actually, I am doing an investigation regarding the failure of an expansion bellow.
The situation is like this...
The existing pipe (built: year 1981) has an existing expansion bellow but in several years these bellow was broken. They decided to replace it with new bellow (using the data from old requisition/specs.) but with different vendor. But upon installation and testing as the maintenance reported, the new bellow only last for 3 hours and there is already a leak in the weld joint. They decided to temporarily install a pipe spool in replaced with the broken bellow and they wonder about the effect of the spool (although the leakage was solved after installing the spool). They were not sure about the future effect of it in the pipe.
Upon investigation, I decided to ask for their oldest bellow (the one that last for several years) and I saw a flat bar (not tie rods) welded in both flanges of the oldest bellow. Now my question is, Is this right or acceptable according to your experience? I thought tie rod is the only way to restrict the axial movement/thust. The new bellow that last for 3 hours only used tie rod. And I was suspecting maybe the welded flat bar (OLDEST BELLOW) vs. the tie rod (NEW BELLOW) is the main difference of their design. Am I right? Correct me if I am wrong.
Please help me clarify the issue and hope for your opinion.
[See attachment for the photo. I deleted the word "NOT"]
Sincerely,
marchie
RE: Metal Expansion Joint
RE: Metal Expansion Joint
I agree with you. Does the effect of these flat bars will be the same with tie rods?
The client actually wondering why the new bellow (w/ tie rods) only last for 3 hrs while the old bellow (w/ flat bars) last for several years? Both old and new bellow have the same design specification but different vendor. What's wrong with the new bellow?
RE: Metal Expansion Joint
Are you sure these bars were meant to be permanent? They look to me like they were there to protect the bellows during shipping??
If they are meant to be permanent and assuming one end is free, they are limiting the bellows in x and y planes, but not Z. If both ends are fixed then it is not clear what the bellows are doing.
Tie rods only restrain movement if it goes beyond a certain axial( Z) component and do very little in X and Y, though this does depend on the design and fixing of the tie rod ends - do you have a photo or drawing of the replacement bellows?
however I can't see any serious welding on either end of those flat bars so it's a bit of a puzzle at the moment.
I can only guess at the moment that the tie-rods are not limiting some sort of movement which is outside the bellows movement limits which the flat bars prevented. However we don't have the data yet.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Metal Expansion Joint
Question: The picture of the old Expansion Joint appears to have the two flat bars welded at 120 degrees apart. Is that correct? Is there a third bar on the far side where we do not see it in the picture?
If there are three bars this would result in a very rigid element and the bellows would be nonfunctional. Why did the original (1981) installation require/have an expansion joint?
You did not provide any information on the commodity. What is it? What is the operating Temperature? What is the Operation Pressure? The Piping appears to be Class 150, is that correct?
Sometimes its possible to do all the right things and still get bad results
RE: Metal Expansion Joint
"..the bellows would be non-functional". This is an incorrect statement. Yes one end of the bellows cannot move relative to the other du to the tie bars but the bellows would accommodate the expension between the two ends, similar to an axial tied bellows. So unless you know the exact reason for the bellows installation you cannot say "the bellows would be non-functional.
RE: Metal Expansion Joint
If those bars are welded to both EJ flanges, there will be no movement between the two ends. Therefore the joint is worthless.
Another question: Why is there no EJ on the Suction side of the Pump?
Sometimes its possible to do all the right things and still get bad results
RE: Metal Expansion Joint
Temperature and a rough idea of pipe layout would likely give quite a bit of information about this situation. It may be that the original design info on the datasheet was inadequate but you happened to end up with a more robust expansion joint than necessary. And now the replacement was designed to just meet the design conditions and it doesn't meet what it's actually experiencing in the field. A bit of speculation there.
Thanks,
Ehzin
RE: Metal Expansion Joint
Thank you for all your comment.
Actually, I did not take those pictures but I guess it might be 3 flat bars welded at 120deg and the flanges used are slip-on & 300#. Also they just installed those spools without consulting first that is why all the information that was given by the client is all history. The datasheet they provided are very old and incomplete. But based on my initial analysis (using the spool) the pump nozzle is exceeding the allowable (API-610) at Moment that is why the old design has a bellow. I am currently asking the vendor regarding the design specification of the new bellow (that last only 3 hrs), maybe there is some discrepancy with the old and new bellow's design specification.
It is really hard to gather all the information specially if the plant was built 3 decades ago and I did not saw the actual situation.
Sincerely,
marchie
RE: Metal Expansion Joint
Sometimes its possible to do all the right things and still get bad results
RE: Metal Expansion Joint
A possible scenario could be that the original expansion joint design was always inadequate but the bars kept displacement/distortion from damaging the expansion joint. It just happened to lead to excess pump flange loadings, although within reason since you haven't noted any major pump issues. When you installed it the "right" way the joint failed because the design was wrong from the beginning. Once again, this is speculation.
If you've any kind of modeling performed for the pipe routing with the expansion joint look and see what the axial/lateral/angular displacements are on the joint and compare to the data sheet. I'm not entirely positive what expansion joint data looks like in Caesar II reports but I imagine this information could be gleaned from it.
Thanks,
Ehzin
RE: Metal Expansion Joint
How much linear expansion is there going to be in a vertical pump discharge line that's maybe 20 feet long?
Then again, LI said: "They look to me like they were there to protect the bellows during shipping?"
RE: Metal Expansion Joint
RE: Metal Expansion Joint
RE: Metal Expansion Joint
After a short period of time maybe everyone thought they were part of the design!
that's why nowadays things like this are painted yellow with a remove before use painted on it.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Metal Expansion Joint
RE: Metal Expansion Joint
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Metal Expansion Joint
Our client decided to design new expansion joint but still I need your help because its my first time to design an expansion joint.
I just want to ask on how to design new expansion joint. The following questions are:
1.) What are the information that I need to submit to the vendor of expansion joint?
2.) How to determine the movements (Axial, Lateral, Angular)? Is that through CAESAR II displacement report from pump expansion (because the line is connected after the flange of pump discharge) OR from the location of the expansion joint?
3.) How to determine the thickness of the bellow?
4.) How to determine the no. of ply if it is connected to pump?
I will also read the EJMA but still I need your expertise to guide me through.
Thank you and hope for your support.
Sincerely,
marchie
RE: Metal Expansion Joint
2) Yes, you need a calculation of teh movements.
3) The vendor will provide you all the info.
4) ?
RE: Metal Expansion Joint
you say "If those bars are welded to both EJ flanges, there will be no movement between the two ends. Therefore the joint is worthless." That is pure BS. The expansion of the length of pipe that would have been there if it were hard piped is accommodated by the EJ. So there would be no relative movement of the ends but there would be movement withint he convolutions of the bellows. The tie-bars are there to prevent the pressure thrust coming into the equation.
RE: Metal Expansion Joint
I agree that it would remove a large portion of the thermal growth for THAT section while not introducing an extreme pressure thrust due to the bars. However, I think removing that growth could be minimal. I don't see it in the earlier pictures or previous comments but removing the growth from ~1-2 feet of pipe won't do much if you still have 10+ feet of pipe in the same direction.
Thanks,
Ehzin
RE: Metal Expansion Joint
Did I say it would be the total solution - no. I was just saying what the bellows would be doing and laterly correcting Pennpipers mis-conception that the joint would be worthless. It may be that during the original installation the Tie bars were never removed as they should have been or perhaps someone thought about the pressure thrust "late in the day" and concluded that the best way forward was to install the tie-bars and consider the section as being rigid. Who knows until the system is reviewed/analysed. All comments are pure speculation!!!!