I've created that file. Please evaluate & feedback.
A consultant's opinion shows that there will be an upward force of 2223KN at the top elbow & a 2823 KN at the bottom elbow of the riser. Please advise.

This is a closed loop HVAC system.

Hi Hazem,

My name is Shawn. I am looking into your model. Please tell me which node of the top elbow and bottom elbow where those forces are applied. Also, what type of force? Member force or restraint force, and in which load cases?

Thanks,

Shawn

I must get out more.

I had a look at this and have never seen any thing like it.
I would be intrested to understand the idea of joining the two sections of pipe without defining all directions of freedom.
I would also be interested in how caesar would cope with a d/t of 1/120

by visual observation the nozzles are in trouble from the weight of the vertical pipe.
but hey, what do i know..

Hi Shawn & Superpiper,

This is a chilled water riser. The two anchors at the extreems are not nozzles but rather borders signifying a section of a long line. The consultant I refered to suggested installing a dummy leg or trunnion at the bottom elbow on which a restraint force of 2823 KN will act downwards in the operating case. Feeling thatthis is a big load, I modified his model by adding a victaulic at nodes 45 & 170 as well as a simple support at 15. He is using a short radius elbows (!?) which I didn't try to change. He used a program named "RM". Heard of it?

I've neglected CAESAR's warning regarding the d/t ratio.
My main focus was the loads. I'm affraid I don't understand....

"I would be intrested to understand the idea of joining the two sections of pipe without defining all directions of freedom." ??

Please clarify.

Thanks for your time.

I dont do this kind of thing (size etc), but i was thinking of it going home. (sad eh?)

1. This is a big pipe. hence big loads
2. This rises some 36 metres which is a hell of a height.
3. This is a large d/t
4. The temperature deltas are very low.

Commenting:

* Model a bit more of the connecting pipe. preferably to a fixed point or, add an anchor and see what happens.

* Take advice about large D/t (i dont know)
* Like so many analysis' this is a problem of forces, not stress
* I would think FEA is required to design a vertical support(s) which is able to handle the large vertical loads
*I would be wary of using a spring, load variations between empty and full pipe are large
*Victualic flanges? nope. do not flange if possible, or use something substantial (weldneck)
* suggest re-route to break up vertical rise
* suggest consutant be involved in support checking (design)
* look for wind loadings?
* Take a long hard look at what is happening at the wall of the pipe.


Treat this as what it is, a large cold pipe! visual analysis first,computer last.
The loads are the controlling factor.
I suspect that even if you can design a support that the pipe wall will accept, then the structural guys will reject 30 ton loads on there rack.

If so, and this large single rise is still required, then maybe think outside the box!(ie split the line in two going up the rises)


some thoughts and good luck.

oh, and with due respect, if you dont know how to design supports (i dont!) then find someone who can.

A note of caution....

CAESAR II is a beam element program it does not understand or obey the laws of hydraulics....

So if you have a vertical line filled with liquid CAESAR II calculates the weight of the liquid per lineal measure of the pipe.... however in the real world if we have a vertical pipe with no valve at the bottom and a open discharge at the end of the pipe the only weight that will be seen is the pipe weight itself. The column of liquid is not attached or restrained by the pipe.

This is also true if the line discharges into a vessel or pump so the length of risers weight may be less than what you will really experience.

Now if you have a valve on the bottom and close it off then the risers weight will include the liquid column. Mull it over...

Hi Hazem,

For node 45 with cnode of 46, the Y restraint is not in effect because the gap of 10 mm (both + and -) is not closed in operating condition. Same thing happens at node 60 with cnode of 61 and node 90 with cnode of 91.

For the section from 30 to 45, Caesar II includes the internal fluid weight, it increases the vertical load at elbow 30. To compensate this vertical load, you need to add an upward force at node 30. The force should be equal to the internal fluid weight from 30 to 45. As I mention, the Y restraint between node 45 and 46 is not in effect, the fluid weight down the node 46 is not carried by node 45.

The Y restraints between 60 and 61, 90 and 91 are not in effect. From 46 to 60, Caesar II adds the fluid weight on +Y at 50. From 61 to 90, Caesar II adds the fluid weight on +Y at 80. To compensate those restraint loads, you need to add an upward force at node 50 which is equal to the fluid weight from 46 to 60, also add an upward force at node 80 which is equal to the fluid weight from 61 to 90.

For the section from node 91 to node 130, I would suggest adding an upward force at node 110 which is equal to fluid weight of this section, and adding an downward force at node 130 which is equal to the fluid weight of the entire riser, from node 30 to 130.

It is very clear that the added forces are balanced. They are just used to adjust member forces (mostly axial) of each element to correct the false and default fluid weight calculation.


Regards,

Hi Shawn & John,

First of all thanks a lot for your valuable remarks.

What I gathered from your remarks is that under operating conditions (ambient T=45 deg. C, Operating T=5 deg.C & P=16 bars), the rigid +Y supports at nodes 50, 80 & 110 will only bear the weight of steel pipe. On the other hand, when the system is shutdown, these supports will carry the steel pipe as well as the water weight. CAESAR II, however, adds the water weight to the operating condition. Thus, I have to input the forces mentioned by SHAWN to negate that weight of water.

Now let me give you more details about the consultant's claim:
He has carried out his calculations on a 34 meters high riser having two +Y supports, one near the top elbow & another around the middle of the riser. Each of these two +Y supports is supplemented by a victaulic coupling below it. Also, he put a dummy leg under the bottom elbow.

According to him, in the operating case, the top elbow will have a load of pipe cross sectional area times presseure (1.7639 sq.m. X 1260 KP = 2223 KN) (The pressure has droped from 16 bars to 12.6 bars at the top of the 34 m riser). The bottom elbow will have the same load in addition to the water weight (approx. 600 KN)??

Regards,

I don't buy all this water weights etc.
and i think you are aproaching this from the wrong angle.
This is a problem of fundementals.
Grooved victualic flanges are totally inappropriate and do not supplement or aid thermal expansion (in my opinion)

I would personally, run the system fully welded and hang(support)
the riser from a support before the elbow, then guide the rise appropriatly in the vertical, and space the supports on the bottom appropriatly. I would then look at the forces and weights
acting on the elbow and the support to see if they are acceptable and workable.
If not, i would maybe look at supporting the riser via a couple of trunnions and checking same.
If not, then maybe breaking up the rise, of reducing the bore.
I would worry about springs and i would be concerned about unstable column effects if supporting on the bottom elbow.
i cant help but think all the talk of forces etc is a side issue.

Tim


edit to say i'll be supprised if a single support at the top is ok!

I'll try that SUPERPIPER.

Shawn, after adding the forces, how should the load cases become?
We now have F1, WW & WNC in addition to the original W, T1 & P1.

This is the first time I go into this kind of cases.

There is no possibility of substituting this big pipe by two smaller ones. Also, no possibility of welding such a large bore pipe.

As I mentioned earlier, this is an HVAC chilled water system. When it's running, we have temp. of 5 deg. C & press. of 16 bars. When it's shut down, the temp. will rise over time to the ambient (45 deg. C Saudi Arabia) yet the system remains under pressure.

I'm begining to think that the consultant has foreseen the huge loads at the elbows in the "shutdown" case!!??


Regards,

First let me say that the WWW is a resource akin to a library.... one must look in the, library... find and read the appropriate references and failing to find any information regarding your problem then ask for help....

This was not the case done here.... See the attached sketch of what you have modeled along with an excerpt from the Victaulic company describing exactly your situation.... do your research there rather than here! We are all employed to do OUR OWN WORK! So if you have a Victaulic Piping question read through the extensive free information available at their web site TSK TSK TSK…..