deutsch english po-russki
Start | Basics Blasting Technology



6.5 Compressor unit / quality of compressed air

The actual compressor unit begins at that point where the atmospheric air is drawn in, and it usually finishes where the prepared compressed air is fed into the distributor network.

Apart from the compressor the following components are necessary or possible:
- Suction pipe / vacuum filter / air intake silencer,
- Electrical supply unit including switching devices,
- Coolant supply and removal unit,
- Recooling plant,
- Aftercooler / condensate trap,
- Compressed-air dryer / fine filter
- Pressure tank,
- Installations for sound damping.

Compressors can be erected on a concrete foundation or without foundation.
The components of the unit can be installed “freely” in the space, or they form – as a compact unit – a closed plant for the generation of compressed air.

At any time, a low ambient temperature is to provide for the compressor (ventilation and exhaustion):
At a suction temperature of about 3°C each the useful supplied volume decreases by 1%.

Wet deposition (condensate trap) constitutes an important factor to obtain an appropriate quality of the compressed air.

An aftercooler should be therefore spaciously dimensioned.

If the consuming units require higher qualities of compressed air, then additional compressed-air dryers will have to be installed.

Refrigeration dryers and adsorption dryers are the most common versions.

If the generated compressed air contains oil then a considerable oil separation will result from moisture extraction. Additional special oil-water-separators might become necessary for allowing the oil to separate from the condensate.


Quality of compressed air

Quality of compressed air

Click to enlarge!



6.6 Processing of compressed air

In order to avoid any disturbances dry and oil-free compressed air is required for blasting processes with compressed air (injector and compressed-air blasting). The processing of compressed air therefore plays an important role. The water contained in the compressed air causes corrosion within the compressed-air network and influences negatively the operation of the tools; this could lead to considerable subsequent costs. This occurrence of condensate causes corrosion in the blasting pot during blasting processes with metallic abrasives. Furthermore, the abrasive forms lumps which could clog the pot.

6.6.1 Aftercooler

The aftercooler is the first and most important step of processing compressed air. It operates according to the principle of a heat exchanger. Air or water can be alternatively used as cooling medium. By reducing the temperature of the compressed air water vapour condensates and is separated from the air via secondary centrifugal collector.


6.6.2 Refrigeration dryer

Due to the physical property of warm air to absorb more moisture than cold air this method reduces the dew point of the pressure by cooling the compressed air. It is usually fixed between +0.3°C and +3°C to avoid freezing of the surface of the heat exchanger. In the air/air-heat exchanger the air flowing in heats the cooled compressed air flowing out. By this the own temperature already decreases, and condensate already forms. In the air/coolant-heat exchanger the compressed air is cooled down to the value entered at the control penal. The condensate that is produced here and consists of water and oil is drained off via a trap to the outside. There the condensate is separated in water and oil.


6.6.3 Adsorption dryer (physical method)

The plant mainly consists of two chambers arranged in parallel which are filled with a water-resistant drying agent. When the compressed air containing moisture penetrates the drying agent in the first chamber the compressed air is dried. In parallel to the drying process, regeneration of the drying agent is carried out in the second chamber. This process requires about 15% of the dried air from the first chamber. The regeneration air generated by adsorption is further dried by expansion from operating pressure to atmospheric pressure and desorbs the previously introduced amount of water. The moisture absorbed by the dried air is delivered into the ambient air via a drain valve. The adsorption chambers are impinged alternately at fixed intervals.


6.6.4 Adsorption dryer (chemical method)

Moisture is absorbed by a solid drying agent. Those can be divided both into solid, insoluble drying agents like dewatered lime and magnesium perchlorate, as well as into soluble drying agents like lithium chloride and calcium chloride. Whereas the insoluble drying agents do not liquify after chemical reaction with water vapour the soluble drying agents liquify in case of progressive absorption. It is disadvantageous that smaller particles of the drying agent are absorbed by the compressed air and this might lead to increased corrosion within the system.


Opportunities of compressed air - processing

Opportunities of compressed air - processing

Click to enlarge!