Air volume in the tank, volume vs pressure

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Discussion Overview

The discussion revolves around the relationship between the volume of air in a tank and the pressure it can hold, specifically comparing a 5-gallon tank at 160 psi with a 2.5-gallon tank at 320 psi. The inquiry includes whether these tanks are equivalent in terms of air volume and pressure, and seeks a formula for understanding this ratio.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions if a 5-gallon tank at 160 psi is equivalent to a 2.5-gallon tank at 320 psi.
  • Another participant asserts that they are equivalent, but does not clarify the conditions under which this equivalence holds.
  • A third participant notes that if the pressures are absolute, the equivalence may hold, but highlights that pressures are often expressed as gauge pressure, which could affect the comparison.
  • It is mentioned that gauge pressure is relevant when measuring how much air will be available from the tank before it is considered "empty."

Areas of Agreement / Disagreement

Participants express differing views on the equivalence of the tanks, with some asserting they are equivalent under certain conditions while others raise concerns about the implications of gauge versus absolute pressure. The discussion remains unresolved regarding the precise relationship and conditions for equivalence.

Contextual Notes

There is a lack of clarity on whether the pressures discussed are absolute or gauge, which may influence the interpretation of the tanks' equivalence. Additionally, the formula for determining the ratio of volume to pressure is not provided, leaving that aspect open for further exploration.

bad_student
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Most air tanks are categorized on volume of air they hold . The question I have is this that a 5 gal air tank that holds 160 psi , is it equivalent to a tank that holds 2.5 gal of air at 320 PSI ?

if not then is there a formula to figure this ratio .

Thanks
 
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bad_student said:
New to forum
Welcome to PF!
Most air tanks are categorized on volume of air they hold . The question I have is this that a 5 gal air tank that holds 160 psi , is it equivalent to a tank that holds 2.5 gal of air at 320 PSI ?
Yes.
 
Yes, if those are absolute pressures. But pressures in tanks are often expressed as gauge pressure, which is absolute pressure minus 14.7 psi.
 
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If you are attempting to measure how much air will come out of the tank before it is "empty" then gauge pressure is an appropriate measure.

By "empty", I mean gauge pressure zero.
 

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