steve.h
Fire Starter,,,,
- Messages
- 348
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- swindon sn4
Hi All, I know it is an age old question about using the propane cylinders as compressor tanks, as well as how to clean them out safely etc.
My question is how many litres of air it would hold at say 120psi, I have not been able to find a good answer to the question, I did however find the below calculation online....
Compressed Air Calculations
A standard cubic foot of air is the amount of air in one cubic foot of space at 70 degrees F and 14.7 PSIA, i.e. standard atmospheric conditions. Since pressure gauges do not register atmospheric pressure, 14.7 PSIA equates to 0 PSIG. Because this is approximately the way air exists in nature, air at atmospheric conditions is also called "free air". Therefore, 1 Standard Cubic Foot of air is the same as I cubic foot of free air.
A tank with a volume of 4 cubic feet holds 4 Standard Cubic Feet of air at atmospheric pressure (0 PSIG). If we inject air into the tank until the internal pressure is 44.1 PSIG, we have 4 cubic feet of air at 44.1 PSIG. How many Standard Cubic Feet of air is this?
Answer: Divide 44.1 by 14.7 = 3. This means that at 44.1 PSIG each cubic foot will contain three atmospheres plus the original 1 atmosphere that existed before pressurizing, or a total of 4 atmospheres. Multiply 4 cubic feet of volume by 4 atmospheres = 16 Standard Cubic Feet of air.
If we inject more air and double the pressure to 88.2 PSIG, the same math tells us we have 28 Standard Cubic Feet of air in the 4 cubic foot tank (88.2/14.7 = 6 atmospheres + 1 atmosphere = 7 atmospheres x 4 cu. ft = 28 SCF).
By using this standard unit of measurement we greatly simplify discussions and calculations of air volumes.
So my understanding and using a couple of calculators cubic centimeters in a cylinder calculator said a 129 cm high cylinder 37.5 cm diameter gives 570133 cubic centimeters, and then cc to cubic feet goes to a tad over 20 cubic feet, so 20 cubic feet is 566 cubic litres.
So if this is the case, and 44 PSI is 3 atmospheres plus the original atmosphere that would make the gas cylinder hold 2264 litres of comressed air, but I said originally about 120 PSI, so that would be three times that 2264, so giving 6792 litres of comressed air in the 47kg cylinder at 120 PSI... Or would it just be the 566 cubic litres ???
I expect I have got it totally wrong, all I want to know is if I used a 47kg cylinder at 120PSI how many litres of air would it hold....
I am just confused....
My question is how many litres of air it would hold at say 120psi, I have not been able to find a good answer to the question, I did however find the below calculation online....
Compressed Air Calculations
A standard cubic foot of air is the amount of air in one cubic foot of space at 70 degrees F and 14.7 PSIA, i.e. standard atmospheric conditions. Since pressure gauges do not register atmospheric pressure, 14.7 PSIA equates to 0 PSIG. Because this is approximately the way air exists in nature, air at atmospheric conditions is also called "free air". Therefore, 1 Standard Cubic Foot of air is the same as I cubic foot of free air.
A tank with a volume of 4 cubic feet holds 4 Standard Cubic Feet of air at atmospheric pressure (0 PSIG). If we inject air into the tank until the internal pressure is 44.1 PSIG, we have 4 cubic feet of air at 44.1 PSIG. How many Standard Cubic Feet of air is this?
Answer: Divide 44.1 by 14.7 = 3. This means that at 44.1 PSIG each cubic foot will contain three atmospheres plus the original 1 atmosphere that existed before pressurizing, or a total of 4 atmospheres. Multiply 4 cubic feet of volume by 4 atmospheres = 16 Standard Cubic Feet of air.
If we inject more air and double the pressure to 88.2 PSIG, the same math tells us we have 28 Standard Cubic Feet of air in the 4 cubic foot tank (88.2/14.7 = 6 atmospheres + 1 atmosphere = 7 atmospheres x 4 cu. ft = 28 SCF).
By using this standard unit of measurement we greatly simplify discussions and calculations of air volumes.
So my understanding and using a couple of calculators cubic centimeters in a cylinder calculator said a 129 cm high cylinder 37.5 cm diameter gives 570133 cubic centimeters, and then cc to cubic feet goes to a tad over 20 cubic feet, so 20 cubic feet is 566 cubic litres.
So if this is the case, and 44 PSI is 3 atmospheres plus the original atmosphere that would make the gas cylinder hold 2264 litres of comressed air, but I said originally about 120 PSI, so that would be three times that 2264, so giving 6792 litres of comressed air in the 47kg cylinder at 120 PSI... Or would it just be the 566 cubic litres ???
I expect I have got it totally wrong, all I want to know is if I used a 47kg cylinder at 120PSI how many litres of air would it hold....
I am just confused....