Oil Storage Tank 1

[durcan]

Looking at designing a cooking oil storage tank which has to staore 17,500 Liters of cooking oil. Can any body give me any tips, to get the presure on the side of the tank, i take the densidy x height x 9.81, for a given point, am i correct?
The tank will also need a support frame, any body any experance in design such a tank.

Tanks

 

[desertfox]

Hi durcan

Yes you're right with your formula the pressure at any depth
in a liquid is given by "density" x "height" x 9.81.
Remember that the bottom of the tank will see the most pressure and this pressure will be uniform across the tank bottom.
As regards a support frame I may be able to help however you need to give the shape and size of the tank first and its material thickness.


regards
desertfox

thickness

 

[durcan]

Hi, more info on tank
all stainless steel
dia 2500 mm, height 3350mm, 3mm wall
cone bottom dia 2500mm going down to dia 154.2mm height 820 mm
It vol. approx 17,500 Liters.

I have some outer supports (ribs), my pressure is .40405 mPa
on the cone and .32228 mPa on the cylinder, these are the maxium values.
My ribs were going to be 12.7mm thick and tappering in to the top? starting at 200mm, with 150mm 12.7mm thich ribs running around the tank.
Where the main problem seams to be is where the cylinder & cone joins, Will I need some extra support? I don't mind adding more in that area.

 

[desertfox]

Hi durcan

I cannot get the same max pressure's using the formula discussed earlier ie:-

density x height x 9.81

according to my calcs and using an oil density of 918kg/m^3

918 x 3.35 x 9.81= 30168.693 N/m^2 for the cylinder part

and adding the 0.82m for the cone I get :-

918 x 4.17 x 9.81= 37553.2686 N/m^2

Now even with the pressure I have calculated above the hoop stress at the welded seam is 12.57 N/mm^2 which is very low.

I have based my hoop stress calculation on "Roarks formula's for stress and strain" page 448 case 1b and before anybody rushes in to correct me, yes the formula I used is based on a uniform pressure throughout the length of the vessel and I have used it to determine maximum stress at the intersection of the cone and cylinder.
Now using a similar scenario and calculating the hoop stress based on a cone per the same book page 449 case 2a
the hoop stress maximum would be 18.3657 N/mm^2 again a very low stress.

In conclusion it would appear that the stresses at the intersection are very small and although there maybe some bending stresses at the intersection due to change of shape
in my opinion these would be neligible.

One point that I find surprising though is that you do not mention any codes that you are working to and I would of thought for this type of vessel and storage of such oils there would be such codes.

regards desertfox

 

[durcan]

Thanks for that fox,
I was using 1000 Kg/m^3 as density, to be on the safe side.
So thats why we had different answers.
I am also out by a factor of 1 so my pressure should be .03 & .04 mPa, as 1Pa = 1N/M^2

I am running my calulation again!

will update

 

[desertfox]

Hi durcan

Okay glad we found our differences, I will watch for your update.
Finally have you managed to find any codes for this type of vessel?

regards desertfox

 

[etf1]

I would suggest you follow BS 799 Part 5. Although this Standard is for storage of petroleum fuel oils, your application could be considered 'similar', for the limited aspects of storage in tanks. The Standard gives details of wall/bottom thickness, reinforcement beam requirements, nozzles and manholes, installation and testing, heating coils, venting, overflow and gauging etc for cylindrical as well as rectangular tanks. I though wish to remind that, strictly speaking, the Standard is not applicable for cooking oil (where relatively higher density and freedom from contamination will be considerations too), but you could draw upon it for some useful guidance. Also, the Standard bases its calculations on carbon steel. You may factor suitably for SS.

 

[durcan]

Hi etf1
Where can i get a copy of this standard?

Thanks

Durcan

 

[etf1]

Hi Durcan,

Sorry, I was away for 3 weeks, so did not read your post untill just now. I can arrange a PDF file of some of the Standard's excerpts, but do not know how to send these to you. I don't think I can attach the file to the Forum's post; nor do I want to infringe upon the copyrights of BSI. I have useful info for you, but guide me how to help you. I am new to Engg Tips.

Warm regards,
etf1

 

[durcan]

please email me on pdurcan@eircom.net, that would be great