A compressor draws in workshop air along with its dust and moisture, then compresses it. At the outlet, this air contains water, particles and traces of oil. For blowing off a chip, that does not matter. For painting a car body or supplying a laser cutter, it does.
Three numbers: particles, water, oil
The ISO 8573-1 standard classifies compressed air quality according to three contaminants. It is written as [A:B:C]:
- A, solid particles: dust, rust, wear residue. The lower the number, the fewer remain.
- B, water: measured by the pressure dew point, the temperature at which the remaining moisture condenses.
- C, oil: liquid, aerosol or vapour, expressed in mg per m³ of air.
Class 1 is the most demanding; the higher the number, the more contaminants the air contains.
Water, the most important point in a workshop
Water damages tools, rusts pipes and causes paint defects. The most common water classes:
| Class | Pressure dew point | How to achieve it |
|---|---|---|
| 4 | +3 °C or lower | Refrigerated dryer |
| 5 | +7 °C or lower | Refrigerated dryer |
| 6 | +10 °C or lower | Refrigerated dryer |
| 1 to 3 | from −20 °C to −70 °C | Desiccant (adsorption) dryer, for very demanding processes |
A refrigerated dryer cools the compressed air, like a refrigerator: the moisture condenses and is removed through a drain. It suits the vast majority of workshops, as long as the room stays frost-free.
Oil and particles: filtration
Line filters stop particles and oil aerosols. They are installed in series: a general-purpose filter, then a fine filter. For the most sensitive uses, an activated carbon filter also retains oil vapour. A filter only works if its element is changed on time: a saturated filter lets contaminants through and causes pressure loss.
Which air for which trade
- Air tools, tyre inflation, blow guns: dry air prevents rust in tools and hoses. A refrigerated dryer and a general-purpose filter are usually enough.
- Painting and body shops: air must reach the spray gun free of water and oil. In practice: refrigerated dryer, fine filtration, and a filter as close as possible to the spray booth. Also follow the recommendations of your paint and spray gun manufacturers.
- Laser cutting: the air is used as the cutting gas and passes through the machine's optics. It must be dry and very clean, at the pressure specified by the laser cutter manufacturer.
What AIRSTAHL compressors provide
The K series 4-in-1 compressors integrate the air receiver, a refrigerated dryer and filtration on the same frame. The L series, designed for laser cutting, goes up to 16 bar with a refrigerated dryer (dew point of 3 to 10 °C) and precision filtration (particles down to 0.01 µm, oil 0.001 ppm, according to the technical data sheet). For the standalone S series screw compressors, we offer dryers and line filters as add-ons.
For a specific need, tell us your trade and your tools in a quote request: we will suggest the matching air treatment.