On account of the 10% ullage, the actual internal volume must be 2500 liters. You then have some choices of shorter with larger diameter, or longer with smaller diameter. There is no one formula for choosing this, because it depends on the sizes and thicknesses of plate that are locally available. You can try several length/diameter options and compare the estimated costs of each. A reasonable first guess might be 1000mm OD x 3500mm long (approximately).

when i assume ID=1000mm

length becomes 1845mm

but the required thickness become 6.2mm

6,8mm thick plates are unavailable.

for 10mm thickness there is no good dia to length ratio .

Your length calculation is off. If t_reqd = 6.2 mm, where does the 6.8 mm come from? Weld efficiency?

its 6.2mm thk required for 1000 ID

6mm and 8mm thk plates are unavailable.

my senior is saying to design it for 10mm thk plate.

ID=1000

L=1845

while calculation for 10mm thk plate are

ID=1597mm

L=77mm

I am unable to understand their logic.

I'm sorry; I misread the 6, 8 mm as 6⁸/₁₀ mm.

I usually work in imperial units, and my SI calculations may be rusty. It's midnight here, so I will look at this again tomorrow.

You can always select a smaller diameter, even if the plate is thicker than needed. This may save on the cost of the heads. What shape do you ordinarily use?

Head type mostly is used elliptic(2:1) for small tanks.

while calculation for 10mm thk plate are

ID=1597mm

L=77mm. it shall be 770 mm , also for 1500 liters

For this diameter: 1000 mm (100 cm) and length 1845mm ( 184.5 cm ) , you can get only 1500 liters , sizes at dwg in [cm] , vol 1449,059 liters

Thanks for such a visual explanation,

volume of shell is 1450 or 1550 liters at 10% ullage

other has been filled by dish ends.

i am having problem for thickness.

i calculate for 8mm but seniors are saying make it ten.

my question is only this that is there any problem/issue except other than economical.

as thickness is directly propotional to diameter.

Your seniors are right

You have to consider corrosion too ! It it depends on many enviromental issues

(good welding+painting-isn"t allways enough)

But when the required thickness is 6.2mm and nominal thickness 8mm. Corrosion allowance has been considered.

It was your´s first post

i have to design 2250water litr capacity bullet horizontal tank for LPG at 10% ullage.

Just to be in consideration that the vol is 2550 liter,

for

8mm thick and 1000 mm diameter, vessel lenght is 3284

for

10 mm thick and 1597 mm diameter, vessel lenght is 1273 mm

As mentioned before, you can always make the vessel diameter smaller than the maximum allowed by the plate thickness. Then consider also the cost of the heads.

This design started at 2250 L (or 2500 to account for ullage). When did it change to 1450/1550?

Another possibility is to make the shell from pipe rather than rolled plate, if the local Code allows.

Volume of vessel=2250Ltrs

ID=1000mm

L=1845mm

Ullage =10%

Volme after ullage=2250*0.9=2025ltr

volume of shell=pi/4(ID^2*L)=(3.146*1^2*1.845)/4=1451ltrs

volume of Both Elliptic heads+both SF=2*[pi/24(ID^2*t)+pi/4(ID^2 *L)]=682ltrs

Abdul....

What has not yet been discussed here is cost and availability of heads.

I suggest that you investigate the standard head sizes available and base your shell length(and volume) on what is available.

For LPG, consider three or four alternatives with the diameter to shell length ratio as 3, 4 and 5. ( or 6)

Your lowest cost will be in there somewhere.

Whwre you lost the 2250 vol to be 1450 vol

You're making a meal of this. The weight of steel does not change significantly with vessel diameter, because if you change dia by factor f, length changes by 1/f², area by 1/f² x f = 1/f, and shell thickness by f. 1/f x f = 1.

So choose what you think is a likely shell thickness and calculate diameter. Then you have dished end volume, subtract that from required total volume and calculate vessel tan-tan. If you think the resulting vessel is too long and thin, repeat using a thicker shell. If you think it's too short and fat, repeat using a thinner shell.