Sizing errors are the most common cause of air compressor problems. A machine that is too small cannot keep pressure stable, while an oversized machine wastes energy. This guide explains the units and a simple sizing method.
Understand the Units
- CFM and m³/min describe air flow, not pressure.
- Bar, PSI and MPa describe working pressure.
- Free air delivery (FAD) is the usable flow at the discharge pressure.
A Simple Sizing Method
- List every air consumer and its CFM rating.
- Apply a simultaneous-use factor to avoid over-sizing.
- Add a leak and expansion margin of 20–30%.
Common Mistakes
- Confusing inlet flow with FAD.
- Ignoring altitude and ambient temperature.
- Forgetting the pressure drop through dryers and filters.
What happens if I buy an undersized compressor?
The machine runs continuously, pressure drops during peak demand and the motor overloads, which shortens component life.
Talk to an Engineer
Contact Panrui with your flow, pressure and air quality requirements to get a recommendation and factory quote for your project.