# 300 gallon tank & 68 psig

1. Aug 15, 2008

### tosh382

I have a double wall steel tank system, where the inner sealed tank is 300 gallons and the outer sealed tank is 600 gallons.

If the inner tank holds 68 psig and begins to leak and the pressure goes out into the outer tank also, is it still 68 psig? If not, is it directly proportional, such that the pressure would become 34 psig?

2. Aug 16, 2008

### Staff: Mentor

The problem is ill-posed.

Is the volume between the inner and outer tank shells 600 gal, or does the 600 gal enclosed by the outer tank also include the inner tank?

What is the initial pressure between inner and outer tanks?

All else the same, pressures equilibrate.

3. Aug 18, 2008

### jaap de vries

Also the leak might work as a throttle valve and therefore, the overall pressure might be less. But basically the problem is Tank A (68 psig, 300 galons) and Tank B (0 psig, 300 gallons) are separated by a partition. What would be the overall pressure after removal of the partition?

Is this the problem?

4. Aug 22, 2008

### stewartcs

If you have one tank (with air in it I presume) with a volume of 300 gallons at 68 psig sitting inside another tank with a volume of 600 gallons and 0 psig and the inner tank leaks, the pressure in the inner tank will not stay the same. It will decrease while the outer tank increases. Eventually they will equalize and be at the same pressure (inner tank lower, outer tank higher, from original pressures).

If you assume it is an ideal gas that undergoes an isentropic process the relationship will be $$Pv^k = constant$$ where k is the ratio of specific heats of the air (typically 1.4).

CS