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Old Jan 14th 2015, 11:28 AM   #1
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Big Problem Need Help

Here is my situation:
I work at a underground gold mine. We have Bio Diesel Fuel Storage Tanks On Surface that we transfer down to a fuel bay storage underground.
We batch 375 Gallons at one time and send it down.
We send it down a 2" sch 40 steel pipe that is connected to a 3"flange ontop of the tank underground. The diesel is being gravity fed down 1600' feet. There is no drop pipe inside the tank once it goes through the 3" flange it is open inside the tank.
The tank is Ul rated 142 and is designed for atmospheric with a max of 2psi in the tank.
I need to put a breather on the tank and a vent line that will go through the breather so i have to vent the tank through the breather and need to know at what rate is the diesel going to be entering the tank. Please help
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Old Jan 15th 2015, 02:38 PM   #2
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Wow guys this must be a really hard question. Did I stump you guys?
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Old Jan 15th 2015, 07:07 PM   #3
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Yes, you did stump us. If you want to determine the velocity of the fuel as it enter the tank it's a very complicated pipe engineering question, not a basic physics question, whose answer will depend on factors that we can only guess at. For example the rate of flow of fluid down a pipe is highly dependent on the viscosity of the fluid - I'm sure there is probably info available on the fluid characteristics of diesel fuel, but only someone versed in pipe engineering would know how to tackle it. They would also need to know whether the route from the surface to the tank a straight vertical drop of 1600 feet, with no bends or turns?

On the other hand if you want to know the rate in gallons/second that's much easier - whatever the flow rate is at the top of the pipe is the same as at the bottom, so it will be determined by how quickly the fuel flows into the pipe. You haven't mentioned how fuel enters the pipe - if simply gravity fed from a storage tank all you need know is the depth pf the fuel in the tank. So please clarify if that's what you mean by rate of flow that you're trying to determine.

If your question is simply about sizing the vent so that air escapes quickly enough to avoid more than a 2 psi pressure gain as the fluid flows in - why not simply make the vent pipe as large as possible (though it wont need to be any bigger than 2" diameter)?

One other point - there should be a vent at the top of the pipe - like there is on waste lines for bathroom fixtures.

Last edited by ChipB; Jan 16th 2015 at 04:28 AM.
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