Nozzle Boundary Condition in pipe flexibility analysis 1

[usecheijk]

Hi!,
In a flexibility pipe analysis, how to modeling a nozzle connected to a pressure vessel at the end of a pipe?, How to modeling the structural stiffness of the vessel? Such stiffness could be replaced by any flexible boundary condition at nozzle?

Thanks in advance,

Jack.

 

[XL83NL]

AutoPIPE has a built in feature that allows one to model the nozzle’s flex based on a few parameters, like OD, tw, etc.
Such methods are also detailed in Peng & Peng’s book, which is an absolute must have for a pipe stress engineer. Those methods explained in there can also be included in a decent pipe stress program if said program doesn’t have a dedicated feature; generally, it’s just a matter of constructing the right beam elements and boundary conditions to physically model the real world phenomena.

Huub
- You never get what you expect, you only get what you inspect.

 

[1503-44]

Enter vessel radius, temperature and nozzle height.
Rotational and axial stiffness can be added if the nozzle is not totally rigid at the point defined above.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[RVAmeche]

In Caesar II you can either define the nozzle displacements at the nozzle (if known) or you can create a sequence of rigid elements to simulate the vessel growth starting from the vessel anchor.

C2 also has the ability to determine API 650 tank nozzle stiffnesses and do WRC calculations, but IMO its better to get that stuff from the vendor.

 

[Alex Matveeff]

This is explained in my complete pipe stress training course

Course agenda download

Short description. Nozzle can be modeled:
[ul]
[li]as an anchor, without flexibility[/li]
[li]as flexible restraint, with local nozzle to shell connection flexibiity[/li]
[li]as flexible restraint, with local and global vessel flexibiity[/li]
[/ul]
The flexibility of the nozzle to shell connection can be calculated using WRC 297 or BS PD 5500 or using finite element analysis (FEA) automatically

WRC 297 method has a lot of restrictions. Only radial nozzles, d/D<0.5, d/T>5, etc.

Finite element method has no restrictions and can be performed automatically.

Need to select flexibilities FEM. Speciy the vessel and nozzle properties

Run FEM analysis

And receive the flexibiities (and also allowable loads or stresses in the nozzle after piping system analysis)

To model the global flexibility of the vessel you can use the cylindrical shell elements:

Sometimes legs of the vessel may be much more flexible than the vessel itself and nozzle to shell junction. And sometimes the steel structures can be more flexible than the vessel and nozzle. In this case need to make something like this:

or like this:

Hope it will be useful

I'm the PASS/START-PROF Pipe Stress Analysis Software Developer