Vacuum Design of Cylindrical Tank

[GasProcess]

I was calculating the safe thickness of a closed dome ended cylindrical tank subjected to vacuum of 20 inches Mercury and normal atmospheric pressure outside. The length between lines of support is 6000 mm and the vessel dia is 60". Material is SA516 Gr-60. The thickness of the shell is about 10 mm.

I am struck because the thickness of the domes is 5 mm and isolated external corrosion with RWT of 3 mm. Could some one please help me to evaluate the tank.

- Should the calculations be performed with 3 mm as thickness for whole tank? or

- Evaluate the domes separately considering them as sphere with 3 mm thickness while evaluating shell as cylider with 10 mm thickness?

- Also please suggest if a patch plate is welded externally over the corroded area, could the thickness of the dome be considered as 5 mm for the full dome.

Thanks in advance

 

[TD2K]

This likely isn't the best forum for ask this question, try:

http://www.eng-tips.com/threadminder.cfm?pid=794

 

[MJCronin]

Agreed....

Re-rating a vessel for new vacuum conditions has been discussed elsewhere and is a more propper topic for the "Boiler and Pressure Vessel" forum.

If this is an ASME coded vessel (you can tell by the vessel nameplate, or the fact that your province follows ASME rules), you must get the vessel re-certified and "repair stamped" by the appropriate authority

This type of calculation is, most commonly, performed by the organization doing the re-rating

-MJC