# Compressed Air

J

#### JW

Does anyone know the formula to calculate compressed air in an accumulator. If I have an accummulator that holds 45 cubic feet at atmospheric, then how much is that when compressed to 80 psig? Thanks JW

E

#### Erich Mertz

You can make an estimate by using the ideal gas law:

P*V = nRT or

Assuming that you cool the gas down after you compress it:

P(1)*V(1)=P(2)*V(2)

Don't forget to use abolute pressure not gauge.

Regards
Erich Mertz

J

#### jmGiraud

For greater accuracy, you may introduce the compressibility factor.
Regards.

W

#### Walter Gonzalez

Assuming that T(1) = T(2), and V(1)=V(2) since the container is the same in both cases, the mass of the gas can be calculated from the following 2
equations:
P(1)*V=N(1)*R*T (1)
P(2)*V=N(2)*R*T (2)
It follows that N(2) is proportional to P(2)*N(1)/P(1)

Walter Gonzalez
Motion Control Engineer

B

#### Bruce Durdle

Simple rule of thumb -
for every 1 atmosphere pressure rise, you need one tank's worth of
additional volume at atmospheris.

So to go from 14.7 psia to 94.7 psia = 94.7/14.7 = 6.5 x, you need
to increase the air quantity by 6.5 x. So you need 45 x 6.5 = 290
scft.

Bruce