## Volume/Pressure calculations

Place for general submarine conversation
I am trying to determine the size of the air reserve tank for my sub. My ballast tank will be about 4L, what size should the air tank be at a pressure of 100psi, 150psi and 200 psi
And what is the formula that would allow me to calculate this ?
Thanks
There are 10 kind of people, those who undertand binary and those who don't !
Sub-Systems

ThierryC
Registered User

Posts: 176
Joined: Fri Feb 21, 2003 3:52 am
Location: Perpignan, France

atmospheric air pressure at sea level is 14.7psia. So if you compress 4L of air to 100psia then the volume of the air tank would need to be under 13% or rougly 1/2L. The formula is:

Vt = Vo * (P + 14.7) / 14.7

where
Vo = ballast tank volume.
Vt = compressed air tank volume.
P = pressure of compressed air in psi.

This is idea so you'll want to add some safety margin. Maybe 10%. If you are trying to make a ballast back up, you don't necessarily need to vent the entire ballast tank. Naturally if your trying to overcome a leak in the ballast tank then you'll need more air.

Jerome
115-1045840519

So little to see and so much time...........

scratch that..............

The formula should have been

Vt = (Vo * 14.7) / (P + 14.7)

And for those nit-picking, yes I earlier stated a compressed air pressure of 100psia in my example. It should have been 100psi.

Jerome
115-1045840519

Thank you very much, that is exactly what I needed !
There are 10 kind of people, those who undertand binary and those who don't !
Sub-Systems

ThierryC
Registered User

Posts: 176
Joined: Fri Feb 21, 2003 3:52 am
Location: Perpignan, France