# Hydraulic press and compressible fluids

1. Apr 18, 2010

### tjrscurieux

Hi everyone,
Here is practical question mixing compressible and none compressible fluids with a hydraulic press. Can the following actually work ? I believe it can but some experience people in this field looking at it may prove me wrong.

Say we have a sphere, 1 cubic meter in volume. The sphere contains 0.5 cubic meter of water and the rest is pressurized air at 10 kg per square cm. There is a tube at the bottom of the sphere, 0.01 meter square. The tube is fill with water and linking the sphere to second part of the hydraulic press which is 0.1 meter square with a weight of 10 kg on it. Now the press cannot lower than the top of the tube and not higher then another 0.1 meter (thus 0.1 cubic meter of water). There is valve between the sphere and the second part of the hydraulic press. Initially the valve is in the close position.

Once the valve is put in the open position, will the press go up 10 cm ?

Now, the air is compressed to 10 kg per square and the tube is 0.01 m square so the hydraulic press with the area of 0.1 m square should be able to lift 100 kg. Since the compress air expands to fill 0.1 cubic m, we take the final pressure from 10 kg per square cm at 0.5 cubic meter to about 8 kg per square cm when we reach 0.6 cubic meter ( 20% less which is equivalent to the increase in volume of the air). So we can lift up to 80 kg on the press. Is this correct ?

If I am correct, someone know which formula can be used to calculate the time it takes for the press to lift 0.1 m given a weight of x kg of it ?