Glossary · Pneumatics and hydraulics
Compressed air
Also known as: Pneumatic air, Plant air
German: Druckluft
In industrial automation, compressed air is atmospheric air compressed to a pressure above ambient and used as an energy carrier for pneumatic drives and tools and as process air. ISO 8573-1 specifies purity classes for particles, water and oil in compressed air.
- Fluid power
In one sentence
Compressed air is air above ambient pressure used to power pneumatic drives and tools; ISO 8573-1 classifies its purity.
Example
The machine requires compressed air at 6 bar with purity class 7:4:4 according to ISO 8573-1, supplied through an FRL unit.
How it applies
- Engineering: Required pressure, flow and air quality are specified for each machine. Leaks and oversized pressure are major sources of energy waste.
- Operation: Pressure drops affect force and speed of pneumatic drives.
- Maintenance: Filters, dryers and condensate drains need regular service; air quality problems cause valve and cylinder failures.
- Documentation: State supply pressure, flow demand and air quality class in the technical data and the installation requirements (Process media specification). Warn that compressed air is Stored energy and describe how to shut off and vent the machine before maintenance. Warn against using compressed air to clean skin or clothing.
Compressed air vs. instrument air
Instrument air is compressed air of higher and guaranteed quality (dry, oil-free) used for control valves and instruments in process plants. Plant air may have lower quality requirements.