Saddles for atmospheric vessel

[ElCidCampeador]

I'm trying to design saddles for an atmospheric vessel. The saddles shall be as shown in this image:

http://www.cordivari.it/media/immagini/2212_n_serbatoio_gasolio_cilindrico_orizzontale_con_piedi.jpg

how can I do? Is there a simple procedure to follow? tnks

 

[TomBarsh]

I guess it's all in the description. I myself would call those "feet" or "legs". Saddles usually indicate some sort of web plate with a circular pocket in which the vessel sits (welded to the shell or not). The analysis generally follows the "Zick" analysis or similar.

But these supports and the shell would not exhibit the same sort of stress distribution. It would seem that the load applied to the shell from the attachment of the "feet" is very localized. It seems that a local-type stress analysis would be appropriate. Such as WRC-107, EN-13445, or FEA, etc. Then the feet themselves need to be designed for the loads they are subjected to.

 

[ElCidCampeador]

It would seem that the load applied to the shell from the attachment of the "feet" is very localized. It seems that a local-type stress analysis would be appropriate. Such as WRC-107, EN-13445, or FEA, etc. Then the feet themselves need to be designed for the loads they are subjected to.

sorry, but now I don't have software in order to apply WRC or EN or FEA. Is there a sort of template? Something that I can use for example. This one is only a tank vessel, not required the application of particular code (In spite of this, I use ASME VIII Div.1 for shell and head) or certification.

 

[JStephen]

The Zick analysis is the standard design method, and covered in Zick's original paper and a number of pressure vessel handbooks. Some experience using it helps, it's not that clear at first glance. It's intended for pressure vessels and if you apply it to thin-shell atmospheric tanks full of liquid, it can be difficult to satisfy the design.
If it is a one-off tank, you can very easily spend more engineering cost analyzing than what you save by your analysis, so it may be worthwhile to use beefier saddles just to avoid additional analysis.

 

[r6155]

This type of supports are made by experienced fabricators without design calculation, with minimum hand calculations and rules of thumbs.
Increases in stress are to be expected particularly in the case of vessels with a ratio of wall thickness/diameter <0,005 whose contents are over 20 m3.

Regards
r6155

 

[MrPDes]

These sorts of leg supports are usually used on very small vessels, where you just use experience and make them really sturdy.

You could size the thickness and size of the legs and weld using some simple conservative everyday engineering calcs to get an idea of what you need, however the design would really need to be proof tested by filling the first tank with water and simulating seismic/Wind etc. In other words, they need to be "designed by experience" or "designed using testing".