Shell thickness standards 4

[vij36]

Respected members,

One of my friend shared a document for determining minimum shell thickness required for hot water (90 deg C) storage tank.
There are two methods, one is CODRES and the other is API 650 method. API method looks simple to me.
We require 20,000 liters capacity hot water storage tank. The water will be stored at 90 Deg Celsius. I am making costing estimates for MS and SS 316.

As per this reference tensile strength of MS is 400 MPa.
MS Tensile Strength
Can I consider the max allowable stress as 400/4 i.e. 100 MPa. Is this correct ?

And for corrosion allowance it is usually 0.0625". Corrosion Allowance

So the design parameters:
Td (Design thickness)= ((2.6xDx(H-1)xG)/Sd) + CA
Dia = 4.5 ft. (formula says ft. but all other dimension in inches ?)
H = 45 ft.
G specific gravity (I took as 1 for 90 deg hot water ?)
Sd 100 MPa. it comes to 14503 lb/sq.in (for mild steel)
CA taken as 0.0625"

Td comes around 2.466 mm

Is this the calculation correct ? Kindly guide.

Thanks,

 

[vij36]

Calculation sheet attached.
Kindly verify

 

[HTURKAK]

I do not want to remind that API 650 tanks are ;above ground, cylindrical, flat bottom, ground supported.

-If the material tensile strength is 400 MPa ( typical A 36 plate. ), it is equal to 58,000 psi and the relevant Product Design Stress Sd 23,200 psi .

-You should look API 650 App.J—SHOP-ASSEMBLED STORAGE TANKS

-The minimum shell thickness ; Copy -paste from the standard

a. For tanks with a diameter less than or equal to 3.2 m (10.5 ft) – 4.8 mm (3/16 in.).
b. For tanks with a diameter greater than 3.2 m (10.5 ft) – 6 mm (0.236 in.).

- The minimum bottom plates shall have a minimum nominal thickness of 6 mm (0.236 in.)

There is specific forum for Storage Tank Engineering. You may post your thread to that forum to get more specific responds.

 

[vij36]

Thank you @HTURKAK. So the minimim thickness is 4.8 mm. Then I would go for 5 mm and bottom plates as 6 mm.
Any other design parameters should I consider please let me know

 

[HTURKAK]

Without knowing the other applicable loads i can not comment. Pls provide more info (applicable wind loading,seismicity , roof type, internal pressure .. ). A sketch showing the dimensions , foundation etc. will be helpful.

 

[bimr]

How did you come up with a 4.5' diameter by 45' high tank? That is probably not the most economical tank design?

Is this tank to be installed on the ground?

SS doesn't require corrosion allowance.

 

[vij36]

Dear Sir,
Because of the peculiar site conditions the tank need to be contained in area of 4.5 ft and 11 ft rectangular foot print. It can be open to sky. So for 4.5 ft dia the height comes about 45 ft to have 20 CBM tank. And the tank will be placed on a concrete platform of 3 ft height. Noted your input on CA for SS. Regards,

 

[bimr]

A two tank arrangement is probably more cost efficient. Each tank being 4.5' diameter by 20 feet high.

 

[vij36]

Ok Sir. Will take estimates for two tank model also. Just want to ensure that the shell thickness remains same i.e. 4.8 mm

 

[bimr]

There is an Indian code for steel tanks conforming to code of practice for use of steel in gravity water tanks IS: 805-1981.

This code calls for 6 mm thickness plus 1.5 mm for water containing salts.

Link

 

[HTURKAK]

Just for curious, how are you planning to compare single tank alternative (Dia = 4.5 ft.,H = 45 ft. ) with double tanks alternative (Dia = 4.5ft.,H =23 ft. ) ?

For double tank case, at least you will need double ( foundations, bottoms, roof and piping ).. If you provide some data for wind, seismicity,safe soil bearing pressure , roof loading , you may get more helpful responds..