How MAHLE Air Drying Cartridges Works For Commecial Vehicles

In this article, we will pull the information from MAHLE official site. Scroll down to learn how MAHLE Air Drying Cartridges work.

Source: MAHLE Aftermarket North America | MAHLE air-drying cartridges—especially for commercial vehicles (

Air dryer cartridges – the guarantee for safe braking in HGVS
More than 2/ 3 of all goods are transported on roads in about 42 million lorries all over Europe. And the trend is upwards. Anybody involved in the transport business will know that breakdowns often have far reaching consequences, of which the financial ones may be of least concern. In order to increase operational safety of the commonly used compressed-air brake systems, air driers have been employed for some time. It can be recognized easily whether a commercial vehicle is fitted with such a system: two conspicuous tanks can be seen between the front and rear axles and some valves, tubes . . . and something that looks like an oversized spin-on filter: the air dryer.

How brakes on trucks work
While passenger cars are normally fitted with hydraulic brakes (using brake fluid), lorries and trailers are equipped with compressed-air brakes. Frequently, a mixed system is used (hydraulic brakes activated by compressed air) in vehicles up to a total weight of 10 tons. From 10 tons upward, mainly compressed-air brakes are used: here the pistons in the wheel cylinders are moved by compressed air. The braking power therefore no longer depends on the power that the driver applies to the brake pedal. The brake is merely controlled via the displacement of the pedal. The compressed-air brake in the trailer works in principle in the same way as in the truck. The required compressed air is provided by the truck via two tube connections. The connection that provides a permanent supply of air to the trailer is marked red and the brake connection that controls the braking operation in the trailer is marked yellow. As mentioned earlier, the air drier is an important safety feature for this type of system.

Why are air dryers needed?
Air contains water vapour. Moist air in an air brake system is especially dangerous, as this can lead to corrosion of important functional parts. In winter it may also block important functions due to freezing. This affects the braking performance – and may lead to total failure. In early compressed-air brake systems it was necessary to drain the air tanks regularly via manually or automatically operated valves. The invention of the air dryer has provided advantages. The background of this ingenuous invention: instead of removing moisture from the system afterwards, it is prevented from entering in the first place. The air dryer removes moisture from the intake air to such an extent that the air cannot release any moisture even when heated up strongly.

This is how an air dryer works

The air from the compressor is cooled initially at the pressure regulator and at the air dryer. Part of the moisture is already lost due to condensation. The air is then fed via a drying agent in the actual air dryer. These granules bind water vapour – the higher the pressure and the lower the temperature, the stronger the effect.

What happens when the air dryer is full?

The granules cannot absorb unlimited amounts of moisture. After the switch-off pressure is reached, the air generated by the compressor is stored in a small tank and afterwards fed back, under low pressure through the drying agent and is then released into the open air. Dissipating the absorbed moisture to the outside regenerates the drying agent.

How long does an air dryer last?

The air dryer is still subject to wear, when the granular material (molecular sieve, in technical jargon) is regenerated regularly. The change intervals stipulated by the vehicle manufacturers indicate when air dryers should be replaced. And from the current catalogue it can be seen, which cartridge from the MAHLE Filter and Knecht range is the optimal replacement for the spent cartridge.

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