Hi, Good day! I am designing stainl

[Lord Ets]

Hi, Good day! I am designing stainless steel and sometimes mild steel storage tank. Our client and my boss always give me the dimension, what liquid to be stored, and design pressure full of water. I always design those tanks using API 650 - Annex V for external pressure. Since there is no data. I always used the maximum which 6.9 kPa. Knowing that I will get a over design tank.

Anyone can help me what is the best assume between 0.25kPa and 6.9kPa for external pressure since it's not specified.

 

[JStephen]

Per API-650, the default external pressure is 1" water column for regular tanks, or zero for tanks with circulation vents per Annex H. See 5.2.1(b).
If in doubt, that's a question for the purchaser and also needs to be coordinated with sizing of vents.
On a small tank, it may not make much difference, but on a large tank, it will.

 

[HTURKAK]

You may design for pressure full of water for test conditions if G of the content is 1.0 or less than 1.0. There are liquids which the relative density G =1.7 or more which your approach will not be correct.


The vacuum pressure shall be decided acc. to size and no. of PV valves and typical internal vacuum is 1 or 2 in WC . For atmospheric tanks vacuum breakers, open vents or PV valves are provided to avoid vacuum collapse . The vacuum pressure should normally be specified by the purchaser.

What are the size of the subject tanks ?

 

[Lord Ets]

JStephen and HTURKAK, the dimensions of the tanks are

11.56m dia x 10.10m height - 2pcs.
12.4m dia x 16.245m height
8.4m dia x 13.52m height
8m dia x 10.48m height
3.95m dia x 5.52m height - with frame.

That's the problem. Always dimensions and location only are the given data. Even soil data was not present.

I have another question regarding of foundation settlement. I designed the tank foundation with mat footing and getting excessive settlement ranging 75-90mm. I don't know if it safe. Rebars and soil bearing cap is already safe, but I doubt with the settlement. Based on your experience, do you have any idea what is the acceptable settlement for the foundation of tanks.

Thank you so much guys. God bless.