Familiarise with High Pressure Terminology
Compressor Dictionary – C
Condensate - Humidity
Condensate is a white, translucent emulsion consisting of water and tiny, suspended oil droplets. Especially when mineral oils are used, the mixture is highly stable and difficult to separate (Anderol 500 is an exception). The oil originates from the "blow by" used to lubricate the compression chamber, the water is humidity from the intake air. The latter condenses when the air is compressed.
At atmospheric pressure, water content depends largely on air temperature; warm air absorbs more water than cold air. For example, at 30 °C a cubic metre of air is saturated (i.e. 100% relative humidity) if it contains 30.4 grams of water. At 50% relative humidity, the same cubic metre of air contains only 15.2 grams. If saturated air cools off, the dew point is reached and water condenses. Cold air simply cannot hold the same amount of water as hot air.
During compression the volume of air decreases drastically. The amount of water vapour contained in the intake air stays the same. Hence, the level of humidity rises sharply, even though the temperature of the compressed air rises concurrently. Once 100% humidity is reached, water vapour condenses because the compressed air is entirely saturated.
The humidity of compressed breathing air is independent from the humidity of intake air. Even extremely dry air will have become fully saturated during compression. However, the amount of condensate varies greatly depending on ambient conditions.
Several methods can be used to separate condensate from air:
- The unfiltered air can be passed through a sinter metal, which causes oil and water vapours to condense.
- A cyclonic separator deflects a jet of unfiltered air so that the heavy oil and water vapours are forced against the housing of the filter tower, condense and trickle down.
- As temperature of the compressed air drops in the inter- and after-coolers, the relative humidity goes up and an oil-water emulsion condenses.
The separators, which are located between the individual compressor stages and after the final stage, collect the liquid condensate.
If the compressor is serviced regularly and properly, the condensate is milky white.
The containers must be drained frequently to ensure optimal breathing air quality; depending on air humidity and temperature 10 to 20 minutes intervals are appropriate. Larger compressor units are equipped with an » automatic condensate drain. Electronically controlled magnetic valves open and close the drain plugs regularly.
If the separators are drained infrequently, the separator vessel may fill up. Liquid seeps into the next compressor stage. Since liquids cannot be compressed, the piston slams into the water contained in the compression chamber. This may cause the compressor to run unevenly or -as a worst case- break down once and for all. These phenomena also occur when liquids are aspirated by the compressor. Flooding the intake tube is certainly the fastest and most effective way of destroying your compressor!
If a compressor is running optimally, the oil content in the condensate is negligible. Because of the small droplets and the even distribution, the oil has a large surface area and degrades naturally in no time. Nevertheless, condensate should be disposed of properly and in an environmentally responsible way.
Drenching a spongy material with condensate and allowing the water to evaporate is a fast and easy method of disposal. The oil adheres to the sponge, which can be discarded at any petrol station.
BAUER's clean air system has revolutionised condensate treatment for small and medium sized compressors. The filter elements, soaked in condensate, are dried by stream of cooling air from the compressor.
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