Air Products Fast Facts: Charts and Tables: Estimating How Much Gas A Cylinder Contains

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Air Products and Chemicals, Inc. -- Fast Facts -- Charts and Tables

Charts and Tables � Estimating How Much Gas a Cylinder Contains*

Use a proportion to approximate the amount of gas remaining in a partially empty cylinder. The pressure and the mass is standard cubic feet or scf of the gas at the time of the filling must be known, as well as the pressure currently in the cylinder. Here's the proportion to use:

Full Cylinder Pressure

Full Capacity

Diminished Cylinder Pressure

Diminished Cylinder Capacity

EXAMPLE: Assume you have a cylinder of Argon 9 inches by 51 inches, which is a type DOT 3AA containing 2,265 psia at a 10% overfill. Total Argon contents are 280 scf at 70°F. What is the cylinder content when the pressure is 1,000 psia?
psia scf	=	psia X scf
1. Multiply 2,492 psia by X scf to get 2,492X. 2. Multiply 280 scf by 1,000 psia to get 280,000. 3. Divide 280,000 by 2,492 to get 112.36 scf (approximately). Therefore, there is 112.36 scf of argon gas remaining in this particular cylinder when the pressure is 1000 psia. Click on the 'Calculate' button to see the calculation performed. You may also enter different values to see additional calculations performed.

Filled pressure and volume are given for a temperature of 70°F. Temperatures above that will produce somewhat higher pressure readings and give a mildly exaggerated value for the contents. Below 70°F, the pressure will be lowered and the volume of gas slightly less than the X-value would indicate. The relationship is approximate for gases whose densities are directly proportional to their absolute temperatures (ideal gas) within a given range of pressures. This relationship also presumes other gas properties, such as compressibility, remain constant within that range of pressure. If the pressure change is large enough, compressibility will change, so other calculation methods should be used.

* Reference: (Ideal Gas Law) Thermodynamics, G. Van Wylen.