API 650 Storage Tank?

[lcmechengr]

I need to design a stainless steel chemical container/storage tank that will be operating at atmsopheric condtions and will be protected from vacuum but it will be configured similar to a vertical pressure vessel with eliptical heads, shell, and support legs welded to the shell. Does API 650 cover this type of vessel/storage tank? If not, what code or standard would this need to conform to? Thanks for any help.

 

[JStephen]

This geometry is not covered by the standard US tank standards. API-650 is for flat-bottom tanks. API-620 includes domed bottoms, but not leg-supported configurations. You can use ASME Section VIII, although it's not pressurized. It's not uncommon to see something like this specced to API-650 or API-620 "to the extent applicable".

 

[massad]

You have to follow ASME Sec VIII Div 1 for such kind of design , since there is no internal pressure so you can use the minimum thickness mentioned in the code , but the vacuum condition governs the actual thickness of the storage tank or vessel.

BR
Assad

 

[JoeTank]

kmechengr,
API-620 covers leg-supported tanks as you have described.

Joe Tank

 

[MJCronin]

What is the stored volume ? If it is more than ~ 45,000 g, a shop built tank may not be a good choice

You may want to consider a tank "deigned, fabricated, inpected and tested to the ASME Code but not stamped". It is unfortunate that there is no formal category for such a vessel, although they are common in the US.

My company recently completed a raw material tank farm comprised of many 20,00 g vertical tanks designed to these requirements. The design pressure of 14 psig ensures a robust, quality tank and enables the tank to be used for several purposes.

Most ASME fabrication shops are familiar with this type of construction.

My opinion only....

-MJC

 

[COSTASTSAPROUNIS]

Here i can see a conflict.
If you follow ASME you will not consider sloshing effect of the liquid in the tank.
I you follow API 650 you will not take into account the stresses in the heads and the local stresses of the legs on the skin.
The allowable stresses in both codes have different definitions.
But you have to follow a guide.
Si in my opinion you should follow ASME but but before this examine the ratio of H/D (height over diameter to see if sloshing is possible).
Costas


Dr. Costas J. Tsaprounis

 

[JoeTank]

Hey Guys,
Some of you are not paying attention. API-620 covers this type of construction too. And seismic sloshing is covered in Appendix L.

Joe Tank

 

[MJCronin]

JoeTank:

Yes, API-620 does seem to apply, but the vague phrase "protected from vacuum" must be evaluated.

I do not believe that an API-620 can be designed to "full vacuum" like an ASME vessel. But, we have to play another guessing game with the original poster to find the actual service conditions.

Dr. Costas:

I do not believe that the structural effects of "sloshing" (typically a seismic loading condition) are a concern of the orignal poster.

My opinion only..

-MJC