 # How to Calculate Compressed Air Consumption

## METHOD 1

### Air consumption is directly proportional to absolute inlet pressure

SCFM2

=

P2 + 1 atmosphere

SCFM1

P1 + 1 atmosphere

Example: A Model 3215 Vortex Tube consumes 15 SCFM at 100 PSIG (425 SLPM @ 6.9 BAR). To calculate the airflow with an inlet pressure of 80 PSIG (5.5 BAR), the calculation is as follows:

English Units:   Metric Units:

SCFM2

=

80 PSIG + 14.7

SLPM2

=

5.158 BAR + 1.0135

15

100 PSIG + 14.7

424.7527

6.8948 BAR + 1.0135

## METHOD 2

### Multiply the known flow by the ratio of the input pressures converted to absolute

Step 1: Calculate the ratio of absolute inlet pressures.
English Units:   Metric Units:

80 PSIG + 14.7

=

0.8256

5.5158 BAR + 1.0135

=

0.8256

100 PSIG + 14.7

6.8948 BAR + 1.0135

Step 2: Multiply known flow by the above ratio you just calculated.
English Units:   Metric Units:

15 SCFM x 0.8256 = 12.384 SCFM

424.7527 SLPM + 0.08256 = 350.6869 SLPM

Therefore

Model 3215 consumes 15 SCFM @ 100 PSIG (425 SLPM @ 6.9 BAR) and will consume 12.4 SCFM @ 80 PSIG (351 SLPM @ 5.5 BAR).

Note: To convert SCFM to SLPM, multiply by the factor 28.3168.

To convert PSIG to BAR multiply by the factor 0.0689