 Air dryer
The air coming from the air filter should actually be clean unless there is a defect in the compressor and engine oil gets into it. Nevertheless, Wabco recommends changing the cartridge more frequently than every two years
if the compressed air contains too much dirt. So not only is air dried here, but it is also filtered again. Moisture is the natural enemy of the compressed air brake system. It is less the threat of corrosion than the blockage of
urgently needed functions when the moisture is released from the air and freezes as water at sub-zero temperatures.
And why isn't the air dryer located in front of the compressor instead of behind it? Well, it wouldn't have to withstand a maximum of 13 bar like this one, but it wouldn't be able to do its job adequately. The more air comes
under pressure and therefore becomes hotter, the lower its possible water content becomes. At 10 bar that's a factor of 10. At least 90 percent of the water content at atmospheric pressure occurs behind the compressor.
Once again for even better understanding: air that warms up releases moisture, air that gets colder absorbs moisture. And this is exactly the effect you use in an air dryer. In principle, its granules absorb all the water as the
air passes through the system. Part of this dried air is passed into a regeneration container with a volume of 4 to 9 liters.
Once the switch-off pressure has been reached, only the air will have a path through the granules to the outside. As the air becomes colder due to relaxation, it takes the water stored in the granules with it. In this way you
prepare the air dryer to absorb moisture again. One speaks of 'regeneration'.
Actually, there is only one area that is not insensitive to cold, namely the outlet of the air coming from the regeneration tank and the valve required here that opens the outlet. To ensure that nothing freezes here, this area is
heated electrically by a heating rod.
It remains to be mentioned that the desiccant box is treated in a similar way to how the oil filter cartridges used to be, which were tightened by hand. Something similar is possible here, namely half a turn after touching the
sealing surface.
| Air dryer with four-circuit protection valve and air tanks |
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