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Treatment of compressed air
Characteristics of air
The presence of dust, moisture and oil vapours in the air contribute to the deposition of scale, which can create
problems for the components as well as deterioration of the distribution network.
Themost frequent problems are:
•Deterioration of the sealing elements in the pneumatic components and the consequent increase in friction.
• Increasedmaintenance costs of components and equipment.
• Increase in cycle time.
• Increased pressure drop and decrease in the final yield.
These impurities must be removed from the compressed air network, as the barriers installed at the compressor
outlet are insufficient, therefore it is essential to fit a
filtering device
at the inlet points.
The filtering devicesmust ensure an optimal air purificationminimizing the drop in pressure.
Characteristics of the fluid
The impurities in the air can be of different types, and depending on the application sector, different purification
needs are required.
In our case, we consider only the elements indicated above, we don’t take bacteriological contaminations into
consideration as we are referring to components and filtration systems used in traditional industries.
The
International Standard ISO-DIN8573-1
defines the characteristics of the fluid on the basis of the classes and
the traditional impurities. The classification ismade according to:
•Number of
solid particles
present in a
m
3
of air relative to their diameter.
• Temperature at which, at constant pressure, the compressed air starts to condense thewater vapour.
Moisture is always present in the air in the form of
water vapour
, to be able to remove it, it is necessary to lower
the temperature by using coolers or dryers.
•Maximum concentration of
oil
.
The table shows themaximum allowable values for all elements according to the defined class.
The quality of air required by components suited for amining environment is not the same as the quality request
from components designed for applications in the food or pharmaceutical sectors.
There are specific filtration systems for the different contaminants, and groups comprised of varying filtration
elements with different characteristics can bemade.
Class
Maximum number of particles present in a
m
3
according to their diameter
0,1 µ
m< d
≤
0,5 µ
m
0,5 µ
m
< d
≤
1 µ
m 1 µm< d
≤
5 µm
1
≤
20.000
≤
400
≤
10
2
≤
400.000
≤
6000
≤
100
3
≤
90.000
≤
1000
4
≤
10.000
5
≤
100.000
Class
Content of water
Temperature of water condensation
1
≤
-70°
2
≤
-40°
3
≤
-20°
4
≤
+3°
5
≤
+7°
6
≤
+10°
Class
Concentration of oil mg/m
3
1
≤
0,01
2
≤
0,1
3
≤
1
4
≤
5
5
≤
5
2
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