API 620 tank design 4

[alienitmeca]

hello

i am designing a vertical storage tank per API 620, i find this standart quit difficult to work with, specially when designing the shell and the roof, i could use a sample of the calculation, if possible, or any advice,

thank you in advance

 

[fegenbush]

Shell course widths are controlled by material availability, fabrication equipment and capacity, shipping restrictions, and field handling restrictions. This is not a question we can answer for you, since we do not know the specifics of your location or that of construction.

The design procedure is assume a thickness -> calculate required thickness -> modify assumed thickness -> repeat as necessary.

 

[alienitmeca]

fegenbush,

thank you for your reply, that was quit helpful for the determination of course number,

but i still don't understand how the first assumed thickness is obtained !! could you explain how to may i get it, since the sample F1 in appendix F per API 650 have choosed 3/4 in !!

thank you in advance

 

[fegenbush]

It is an iterative approach. You must start somewhere, anywhere, then converge on the minimum thickness. If you choose to start at 3/4" as *your* rule, that is fine, but for some tanks it may take a few iterations to get the final solution.

 

[alienitmeca]

fegenbush,

thank you, that was really helpful,


i have another question concernig the roof and bottom design;

- API 620 does not give any specifcations about roofs that need internal structure, where could i find the the Standard that gives such specifications?

- as far as the bottom is concerned, do i use the same design per API-650 (central plates and annular plates (if needed)), if not what should be the criteria for the bottom design?

thank you in advance

 

[DaniMP]

Hi !

Could I use this thread to ask a few questions (I did not find in API 620 / 650 hints or answers regarding these issues) :
- in designing my storage tank, are there some guidelines regarding the diameter / height ratio to observe ?
- do I need to leave some minimum space around the tank in my retention volume ?

Thank you !

 

[fegenbush]

Tank diameter/height ratios and rules-of-thumb therein are based on years of experience designing and building tanks to find out what works and what doesn't. Sometimes the customer pays attention to the decades of experience that the tank contractor possesses, and sometimes they do not. Disregarding the value of this experience and the recommendations it produces are costly mistakes.

Minimum tank spacing is controlled by a number of factors. Often, the local jurisdiction will reference specific codes if the tank is to contain combustible materials (e.g. LNG). NFPA 30 is the most referenced specification in this regard.

/I do plan to get back with the original poster on his new questions, but ballots are due in this week.

 

[IFRs]

Tank height is often controlled by foundation capacity and sometimes restricted by local zoning.
Wind and or seismic considerations can make a lower wider tank more economical.
Available steel grades and thicknesses may limit your height.
I did my negatives first, then all but 12B.
Working on that one...

 

[alienitmeca]

DaniMP,

as far as the tank diameter/height ration, you could check Table A.1a—Typical Sizes and Corresponding Nominal Capacities per API 650, it could help.

 

[alienitmeca]

Hello,

API 620 does not specify when annular bottom plates should be used, could you indicate when they must be used

 

[Tyal51]

Recently I read an "in house" storage tank specification which ended up a mixture of specifications. The intent was good, but one cannot short circuit the tank selection data, design requirements, and installation preference for any particular company. These all need to be separate, but can be included by having different sections with-in the specification. I can see where an inexperienced manager may assign a task of this nature to a junior engineer, with the objective of developing a "simplified design" but take notice of the advice stared in the "Special Notes" of API 650 (05/11/2011) - "Users of this standard should not rely exclusively on the information contained in this document". Sound business, scientific engineering and safety judgment....

Only fools rush in where other fear to tread.