Oz’s of compressed air

Question

A pump sprayer (Vessel A) is 2gal. and has 2gal. of liquid in it w/a pressure rating of 40psi.. (Vessel B) is to keep (Vessel A) pressurized to 40psi.,at an initial pressure of 120psi. in (Vessel B) how many oz. of compressed air will it take to empty (Vessel A) ?

 

Answer 1

Since the 2 gal. vessel A will be filled with air at 40 psi, you need to find the density of the air and multiply times 2 gal. However, you have not specified the temperature of the vessel or the surroundings which affects the value of the density of air.

 

If you assume the temperature to be 70 degrees F, then the air density is .279 lb/ft³ at 40 psi. 

Using that value,

 

2 gal. X (.133681 ft.³ / gal.) x (.279 lb. / ft.³ ) x (16 oz. / lb.) = 1.19 oz. of air at 40 psi

 

(The above conversion factor is for liquid gal. to ft.³

If you need to used dry gal. to ft.³ the factor is .15556.)