Pressure Units
Pressure is force per unit area. In pneumatic systems, it determines the available force.
Absolute vs. Gauge Pressure
| Type | Symbol | Reference |
|---|---|---|
| Absolute | psia, bara | From absolute vacuum (zero) |
| Gauge | psig, barg | From atmospheric pressure |
At sea level: 1 atm = 14.7 psi = 1.013 bar = 101.3 kPa
note
When someone says "7 bar", they usually mean 7 barg (gauge), which equals ~8 bara (absolute).
Conversion Table
| Unit | psi | bar | kPa | kg/cm² | atm |
|---|---|---|---|---|---|
| 1 psi | 1 | 0.0689 | 6.895 | 0.0703 | 0.068 |
| 1 bar | 14.504 | 1 | 100 | 1.02 | 0.987 |
| 1 kPa | 0.145 | 0.01 | 1 | 0.0102 | 0.0099 |
| 1 kg/cm² | 14.22 | 0.981 | 98.07 | 1 | 0.968 |
| 1 atm | 14.696 | 1.013 | 101.3 | 1.033 | 1 |
Typical Pressures by Application
| Application | Typical pressure |
|---|---|
| Pneumatic tools | 87-100 psi (6-7 bar) |
| Automation | 72-87 psi (5-6 bar) |
| PET blowing | 360-580 psi (25-40 bar) |
| High pressure (breathing) | 2,900-4,350 psi (200-300 bar) |
| Low pressure (blowers) | 4-14.5 psi (0.3-1 bar) |
| Industrial vacuum | -7 to -13 psi (-0.5 to -0.9 bar) |