API-650, tank vacuum pressure

[Engr ZANIA]

hello!
I have to design a storage vertical tank of Dia 42m and height 16m having wind velocity of 50 m/sec. For vacuum pressure of -0.6 Kpa (6mm of Hg) appendix V of API650 required two stiffeners with a very large impractical cross-sectional area,Is there any other way to reduce the area avoid it??

 

[MJCronin]

Consider posting in the Storage Tank Forum...

MJCronin
Sr. Process Engineer

 

[JStephen]

First step is see if you're doing something wrong. Depends on the definition of "very large impractical". In particular, watch the units specified in the equations.
One approach always worth checking is to increase the shell thickness so you don't need the stiffeners- try that for comparison.

 

[Engr ZANIA]

I have gone through all the formaula again and again. I have also tried increasing shell thickness but couldn't get anything worthful.in appendix-V atleast two stiffner are required for vacuum pressure greater than .25 kpa

 

[LittleInch]

0.6 kPa is 8mm Hg or 60mm water.

For a 17 high 42m diam tank, that's a lot.

What size are the stiffeners?

API 650 is just not intended for any appreciable vacuum

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[KevinNZ]

Others have looked at this problem

http://www.ast-forum.com/ast_forum_tree.asp?master=10306

https://archive.epa.gov/emergencies/content/fss/web/pdf/lieb_04.pdf

https://www.sciencedirect.com/science/article/pii/S0263823115000683