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1. Nov 16, 2014

### straws

i have a pre made tank approx dimemsions 3x3x3 feet the thickness of tank walls appear to be 3/16 to 1/4 inch thick. with a 1foot square opening on top for filling this opening had a raised "wall" approx 2inches. tank is used to collect used oil for shop heating. (this tank looks like a resturant tank thats in back to collect the cooking oil) currently useing a pump to move oil to and from(way to slow) thinking of have a "pressure" lid made with an air hose quick disconnect to blow/push oil from tank to storage vessel. suggestions? will this idea work?

2. Nov 16, 2014

### Doug Huffman

Yes, it may work. Will the tank withstand the air pressure (force per unit area) plus the hydrostatic pressure of the contents?

3. Nov 16, 2014

### straws

i am not sure...what do i need to find to answer the..force per unit? do i need sq ft of thesides? and not sure what to ask about the hydrostatic pressure? the contents (oil) will be in the thickness or weight of 90w gear oil in warmer months and thicker in colder (winter) months

4. Nov 16, 2014

### Q_Goest

Hi straws. It sounds like you have a square or rectangular tank with flat sides that are made from sheet metal. Even with the thickness you have, the amount of pressure a flat sheet of steel can withstand is minimal. It's on the order of 1 or 2 psi at best. Much more than that and it will permenantly deform and begin to take on the shape of a ball. You can analyze stresses using equations here:
http://www.roymech.co.uk/Useful_Tables/Mechanics/Plates.html
Look at rectangular flat plates.

With 1 or 2 psi inside the box, you won't get much flow. And if you plan on pressurizing the box with a source of compressed air, there should be some way to prevent the pressure from rising above some safe level. It simply won't be able to take much more than a few psi before the sides begin to permenantly deform.

On a legal note, most states in the US have a law that requires vessels meet ASME code and the code defines what a vessel is which has been adopted by the states. If this box is pressurized to 15 psi or more, it would be considered a pressure vessel per the code and since it doesn't comply with ASME code, it would be illegal to pressurize it to that level per state law and you could be fined. Note that this box would probably explode with that much pressure in it anyway.

I'd suggest not trying to pressurize a square box at all. Use a pump if you need to remove oil from it.