1. Why does compressed air need to be treated?
The quality of compressed air is a key factor in the efficiency and longevity of products in the production process. The problem is: untreated compressed air is anything but clean.
Ambient air contains up to 180 million dirt particles (0.1 – 0.01 micron), 5 – 40 g/m³ of water (water vapour) and up to 0.03 mg of oil in the form of mineral oil aerosols and unburnt hydrocarbons per cubic metre. All these contaminants are drawn in and end up in the compressor with the ambient air.
1.1 What happens during the compression process?
When ambient air is compressed, the concentration of contamination increases massively. When compressing to 10 bar operating pressure, 11 m³ of expanded ambient air is drawn in and compressed to an operating volume of 1 m³. This increases the concentration of contaminants elevenfold, to up to 2 billion particles per cubic metre of compressed air. On top of this come lubricating oil and wear particles.
Depending on the design, limit values of
- 250 mg/m³ particles
- 85 mg/m³ water vapour
- 15 mg/m³ oil
are released into the network.
1.2 What are the consequences of contaminated compressed air?
Contaminated compressed air can have negative consequences for the smooth running of production processes, the health of employees, the service life of compressed air tools and air nozzles, and the level of energy and maintenance costs.
Without compressed air treatment, chemically aggressive and harmful particles are not filtered out. Dust and other solid particles cause faster wear of high-quality compressed air components (air guns, air nozzles, air knives or ring nozzles) through abrasion. Moist compressed air can cause corrosion, leaks, mechanical defects and frost damage. Finally, oil in compressed air can lead to contamination of products as well as reduced diameters and blockages.
1.3 Efficient compressed air treatment
The central task of compressed air treatment is therefore to remove contaminants from the compressed air to suit the needs of each industry and production process, providing technically oil-free, clean compressed air in the required quantity at the right place and at the right time.
The key factors for assessing compressed air quality are particle size and quantity, residual water content, pressure dew point and residual oil content. Sensitive industries such as food or pharmaceuticals require particularly high compressed air quality.
Compressed air quality can be classified according to DIN ISO 8573-1 into various purity classes:
Compressed air classes according to ISO 8573-1:2010
| Solids/dust | |||
| Class | max. number of particles per m³ | ||
| with a particle size | |||
| of d [µm]* | |||
| 0.1 ≤ d ≤ 0.5 | 0.5 ≤ d ≤ 1.0 | 1.0 ≤ d ≤ 5.0 | |
| 0 | strengere Anforderungen als Class 1 | ||
| (as specified) | |||
| 1 | ≤ 20,000 | ≤ 400 | ≤ 10 |
| 2 | ≤ 400,000 | ≤ 6000 | ≤ 100 |
| 3 | – | ≤ 90,000 | ≤ 1,000 |
| 4 | – | – | ≤ 10,000 |
| 5 | – | – | ≤ 100,000 |
| Water | |
| Class | Pressure dew point |
| 0 | strengere Anforderungen als Class 1 |
| (as specified) | |
| 1 | ≤ -70 °C |
| 2 | ≤ -40 °C |
| 3 | ≤ -20 °C |
| 4 | ≤ +3 °C |
| 5 | ≤ +7 °C |
| 6 | ≤ +10 °C |
| Oil | |
| Class | Total oil concentration |
| (liquid, aerosol + vapour) | |
| [mg/m³]* | |
| 0 | strengere Anforderungen als Class 1 |
| (as specified) | |
| 1 | ≤ 0.01 |
| 2 | ≤ 0.1 |
| 3 | ≤ 1.0 |
| 4 | ≤ 5.0 |
| X | > 5.0 |
* at reference conditions of 20 °C, 1 bar(a), 0% relative humidity
1.4 Compressed air filtration requirements depending on the desired compressed air quality
Because of the enormous number of particles in compressed air, setting up a filtration train is crucial to the safety and reliability of the production process.
Which filter type or filter combination suits your specific needs depends on which compressed air quality class according to DIN ISO 8573-1 your application requires.
Choosing the right compressed air filters is decisive for compressed air quality. By combining different filters with different filtration grades in the compressed air system, it may be possible to achieve higher purity classes according to DIN ISO 8573-1.
We are happy to advise you on all aspects of compressed air treatment and filtration!