I am working on a piping system which can be divided into 3 different segments based on the fuctional aspects. Like, first there are 4 Manifold, second there are 4 interconnect pipe lines which connects 4manifold to one more system of pipe lines. In this third system, from one 6" line 4 branches are are taken and connected to the interconnect piping via control valves.

My question is , which approach would be better. Should I model everything in Single CAESAR file means all 4 circular manifolds , 4 interconnect pipes and the main supply system. Or it is better to model things seprately like 4 manidfolds in 4 individual CAESAR files , 4 interconnect pipe in other 4 files and the supply system piplines in 1 caesar file and run the analysis seprately.

If I take 2nd approach then what restraints should i put at the connecting points e.g. If one manifold is modelled seprately then at the point where it connects to interconnect pipe should I put restraint as ANCHOR and then use to resulting FORCES and MOMENTS value of the Manifold results as the Input when I run respective interconnect piping analysis. Does this sound meaningful to you? Or is there any other approach for this?

Please suggest.

Hello CHENNAI

Keep it simple. If you split your system in three different systems you should do it in real anchor points where you can add and subtracts loads. In this case the anchor points will act as a mechanical brake between two different parts of the system: What happen in one side of the system has no effect on the other side. In this case the anchor should be designed with the net load on the anchor.
If you split you model in any place different than a real anchor then you will be doing what the software does automatically. You will end copying border conditions such as loads and displacements from one system to the other... chances are that you end spending more time in this than in your actual problem.
If you want to keep everything in separate files for modeling, you can try with including piping input files for analysis.
I would only recommend splitting systems in different models if you know that the other side of the system would never notice whatever you do in one side of the system. Such as the situation on opposite ends of the pipe rack

Regards,

Hi,

I will be splitting the model at points other than real anchors and what happens in one system does affect the other system.

Now, in such a case if I isolate a part for separate analysis, should I put anchors at the connecting points and copy the resulting forces and moments into the input of connecting system

or

should I leave the connecting point as free and copy the displacement of connecting point into the input for the adjoining system.

which will be the right option to simulate the conditions??

Would it be too confusing for me to say either approach is appropriate?

You can start your artificial boundary conditions either way - setting either forces or displacements. But whatever you use to start, you should take these results and apply the opposite (displacements or forces) to the missing systems and see what happens to them. As the other (missing) systems load up or move, you now have a new set of loads or displacements to apply to your original system. You keep on iterating back and forth across these artificial boundarys until they get back to equilibrium.

That's why your probably better off by modeling these systems together - the entire stiffness matrix will keep this "boundary" in equilibrium automatically.

With an eye on system stiffness, you can reduce model size. Say, for example, you have a 4 inch line off a 16 inch header. In terms of load and displacement, the 4 inch line will go wherever the 16 inch line wants because the 4 inch line cannot provide enough load to move the 16 inch line elsewhere. You can specify the 16 inch displacements as the boundary condition on the 4 inch line analysis and believe the numbers without iteration. That's what you do now for hot equipment connections. (Aside, but this would not work if you had 100 4 inch connections off that 16 inch line.)

Your piping system communicates forces and displacements through system stiffness. You cannot arbitrarily stop this movement of information (those forces and displacements) with your casual location of system boundaries.

Thanks Dave,

The concept is clear for me now. And also, I have modelled the everything in a single file there wont be any issue for the timebeing.

But sometimes I have to work upon a some systems in isolation without proper input on whats there in connected system and that time I just get a bit puzzled as to how to simulate the end conditions at the connection points. But as you said I can follow any of the two approach of putting restraint and metioning F & M in results OR keeping the end free and mentionin displacements in the results.

Thanks.