Mainly three components, solids, water content and oil residues contaminate compressed air after compression to a considerable degree. One therefore finds all impurities of the ambient air in compressed form in the compressed air, unless they had been eliminated beforehand. These are joined by further substances originating from the compressor itself or from the piping and compressed air hoses. Compressed air is used as a power medium in the most varied fields. These often differing manufacturing sectors also call for differentiated degrees of compressed air quality. It will be understood that normal working or factory air does not call for the refinement of quality of compressed air except where absolutely necessary in more select fields such as the food or beverage industries. There are also other sensitive manufacturing processes, such as the manufacture of microchips for the electrical industry or the extraction of hygroscopic (adsorbent) materials in chemical factories, which confront compressed air users with widely differing requirements.
Figure 2.5.1
If a compressor draws in 8m3 of air in order to covert this into 1 m3 of compressed air at a pressure of 8 bar, then all contaminants present in atmospheric air (see table 1.7.1.1) likewise become compressed and are therefore present in the compressed air in 8-fold concentration.
Figure 2.5.2 - Characteristic Graphs of Compressed Air Preparation
The increasingly animated discussion in recent years concerning the subject of environmental pollution and of the problems raised by this do, of course, also apply to compressed air. Compressors convey the aspirated air with its impurities in heightened concentration to the point of use, where they are then released at the work place upon decompression. Drawbacks of this kind are in conflict with the requirements which are today demanded from compressed air quality. Optimum conditions can be achieved only through targeted and consciously applied compressed air purification. The solution to this problem is not restricted to the air purification chain after compression but affects all units of the compressed air system, starting with the compressor air intake right up to the point of use.
