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# Calculation of Tank Wall Thickness

## Calculation of Tank Wall Thickness

(OP)
Hi,

Can anybody help on the calculation for the wall thickness of a storage tank 98"OD x 216"straight side? The SS304L tank is vertical with cone top and flat bottom at atmospheric temperature and pressure to hold 67% HNO3 (1.41kg/l or 11.7 lb/gal). We had a proposal with 10gauge SS304L for this tank. But not sure if it is safe for tank with this height. Highly appreciate your advice.

Thank you!

bydublin

### RE: Calculation of Tank Wall Thickness

If this is to be an API 650 tank it will have certain minimum thicknesses.  For this tank that would be 3/16 inch.  To to a proper design you need pressure (internal and external), wind, seismic and temperature, joint efficiencies, etc.  But, you may want to use another code or just good engineering practice and calculations.

### RE: Calculation of Tank Wall Thickness

(OP)
That is the problem! If I go with API650, the price is double. We have a tank (11gauge)for the same purpose, size 10'od x 10'h, which  has been using over 15yrs, problem free. Is there a formula or code to calculate tank wall thickness with given tank OD and height? Where I can find this?

Thanks,

bydublin

### RE: Calculation of Tank Wall Thickness

I suppose you could treat it like a pipe and use classical PD/2T type equations.  Or use API equations but not the minimums.  Etc

### RE: Calculation of Tank Wall Thickness

And look at the "features" [nozz, M/W's. etc] permitted in API-12F.  12F is much more applicable for small tanks.  Building small tanks to API-650 will indeed double the cost of your tank.

If you use 12F, please use a 'doghouse' shaped manway, not the rectangle 12F recommends.  The square corners at the top of a 12F manway generate the highest spots of stress in that tank.  I have had multiple cases of Stress-Corrosion Cracking from those square corners.

### RE: Calculation of Tank Wall Thickness

(OP)
Thanks for all your guys' inputs. I did some research, look like API 650 covering a large range of tank volume. In practice, we don't need a manyway. Can an engineer say his work follow API in this way (no manway in tank). Don't know who is able to work on this? We are in ohio.

Thank you!

### RE: Calculation of Tank Wall Thickness

Does your engineer have a proposal as to how to accomplish the mandatory 20-year Internal Inspx to evaluate the floor??

Manways, side and/or top, appear to be required to me.

### RE: Calculation of Tank Wall Thickness

Dublin.....

While a "homegrown" tank design may not fail, it will be hard to prove that it is safe.

Storage of deadly/dangerous liquids may require a design certified to be in accordance with a nationally recognized Code or Standard.

NFPA-30 requires tanks that store diesel fuel to be in accordance with a UL, API or ASME code. Is your liquid less dangerous than diesel fuel ?

Yes, storage of large amounts of deadly liquids in API-650 stainless steel tanks is expensive.......

### RE: Calculation of Tank Wall Thickness

I imagine that you can buy cheap tanks from China.

### RE: Calculation of Tank Wall Thickness

Just looking at the thickness, the stainless steel minimum allowable thickness for shells and roofs per UL142.  You still have to prove it with calcs.  These are just guideline minimums.  Minimum bottom is 0.158" per UL142 for stainless steel.

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