Pressure in a Tank: Questions & Answers

[rachit mehra]

Hi all, this will seem a very easy problem for you guys but its really a bit conufusing for me..
I work on an oil tanker and the problem is as follows.
What will be the pressure on the filling line of a tank which is on deck when oil is being filled into the tank. For sake op simplicity let's take the density as 1.0. The tank is 20 metres deep and the valves are at bottom.( The entry point is on the top, and the oil flows down to the bottom of the tank and enters the tank at the bottom) . The tank has an inert gas blanket wih a pressure of about 400 mm water gauge.
Now my questions are-
1) What will be the pressure on the bottom line at the valve when a pressure gauge shows a pressure of 1 Bar.
2) If the tank is filled up to a height of 15 metres what will be the pressure then .

Thanks

 

[Volcano]

I suppose there will be a gas with oil too. Is it? Let's choose two points in tank. One is in liquid(A) and other is not(B).

Total pressures,

PA = Pgas + P liq
PB = Pgas

P liq = h d g

Also, if gas can not get out, even filling the tank, gas pressure will grow. If this is an ideal gas then,

PV=nRT

and n, R, T is not changing when filling. Thus,

PV= const.

Say, the gas has P pressure in tank and volume is V then, half of tank filled with liquid. Now,

PV = Pf*V/2 (Pf: Final pressure)
Pf=2P

hope this helps. (If i could understand properly)

 

[charng]

for reaching out with your questions about pressure in a tank. It is important to understand the concept of pressure in order to safely and efficiently fill tanks on an oil tanker.

To answer your first question, the pressure on the bottom line at the valve will depend on the depth of the oil in the tank. As the oil is filled, the pressure at the bottom will increase due to the weight of the oil above it. Using the density of 1.0 and a 20 meter depth, the pressure at the bottom line can be calculated using the formula P = ρgh, where P is pressure, ρ is density, g is the acceleration due to gravity, and h is the height of the oil. With these values, the pressure at the bottom line would be 196 kPa (1.96 bar).

For your second question, if the tank is filled to a height of 15 meters, the pressure at the bottom line will be lower than when it was filled to 20 meters. Using the same formula, the pressure at the bottom line would be 147 kPa (1.47 bar).

It is important to note that these calculations do not take into account the pressure of the inert gas blanket in the tank. This pressure will also affect the overall pressure in the tank, but it would need to be measured separately.

I hope this helps clarify the concept of pressure in a tank for you. If you have any further questions or concerns, please do not hesitate to reach out. Safety is always the top priority when working with tanks on an oil tanker.