When it comes to air dryers, no other name is probably as well known as Bendix. The U.S.-based manufacturing giant is credited for inventing the air brake air dryer for the automotive air brake system. With more than 5 million units sold in North America alone, Bendix air dryers revolutionized the modern air brake system by reducing overall maintenance costs and significantly extending air brake components' service life.

Today, Bendix offers a wide range of air dryer models to accommodate various air brake configurations and applications. One of its most popular models is the Bendix ADP-IP air dryer. Designed for use in heavy duty trucks and trailers, the Bendix ADP-IP air dryer consists of a desiccant cartridge with a lightweight aluminum end cover. The dryer shares the same key competitive technologies with other Bendix desiccant air dryers, including a proprietary oil coalescing filter that removes oil and solid particles from the air before reaching the desiccant medium and a check valve that ensures air flows only in one direction for improved filter performance.

What is the Bendix ADP-IP?

A standard in modern automotive air brake systems, the air dryer is a type of filter that removes moisture from the air processed by the compressor. Compressed air tends to contain more humidity than usual, which can lead to corrosion of the tanks and piping as well as wash out or emulsify grease or lubricants found in the various moving parts of the A/C system. Air dryers prevent this from happening by drawing out moisture from the air stream as soon as they leave the compressor.

Air dryers come in various forms depending on the application. The Bendix ADP-IP air dryer is the desiccant-type air dryer wherein it forces air through porous desiccated media several times to remove water vapor. The dryer does not entirely remove moisture from the compressed air, but it reduces it down to the point that there are not enough water molecules in the air for it to condense.

The charging cycle

Air enters Bendix ADP-IP air dryers through the supply port of the end cover assembly. As it travels inside the end cover, the flow of compressed air changes several times, causing water and other contaminants to condense and drop to the bottom. The compressed air then leaves the end cover into the air dryer desiccant cartridge, wherein it flows through a separator that removes moisture, oil, and remaining solid contaminants. The air then exits the separator and enters a drying column, where it becomes progressively drier as the desiccant material lowers the humidity. Bendix's patented desiccant media is so effective that it can remove up to 95 percent of water vapor from pressurized air.

Once the air passes through the desiccant material, it exits the cartridge through a check valve and fills the purge volume between the cartridge and outer shell. Air will start to be expelled from the dryer cartridge through the purge orifice near the check valve, but most of the remaining air is moved out of the check valve and into the delivery port to the air reservoir. The air dryer remains in this charging cycle until the air brake system pressure reaches the cutout limit.

The purging cycle

After the charging cycle, Bendix air dryers then go to a purge cycle wherein a governor triggers the compressor to unload and cease pressurizing air. During this process, the line linking the governor unloader port to the air dryer end cover control port triggers the dryer to start pressurizing air and forcing its purge valve to open. Contaminants in the end cover sump are then expelled immediately after the opening of the purge valve. Simultaneously, air traveling through the desiccant cartridge changes direction and starts to flow to the purge valve, removing the accumulated oil and solid contaminants in the separator as a result.

The entire process from the purge to the decompression of the desiccant cartridge happens in just a few seconds and is evidenced by the noticeable gusts of air coming out of the air dryer exhaust. It usually takes between 15 to 30 seconds for the entire purge volume to flow through the desiccant drying bed, with the dry air reactivating the desiccant material via the removal of the water vapor it previously absorbed.

To prevent air pressure from the brake system from blowing back into the air dryer during the purge cycle, the Bendix ADP-IP relies on its advanced check valve system. The valve will not close until the air brake system pressure is reduced, and the governor signals the compressor to resume compression and start the next charge cycle.

Dryer maintenance

Another advantage of Bendix air dryers is that they are engineered with reliability in mind. Able to perform reliably even in the harshest conditions, the ADP-IP air dryer requires maintenance at longer intervals compared to similar competing desiccant-type dryers in the market. The manufacturer recommends a checkup of the ADP-IP dryer after three months or 25,000 miles of use, particularly looking for signs of moisture in the opening reservoirs, drain cocks, and valves. If moisture buildup is present, the desiccant cartridge is likely to be too worn out and must be replaced. Once it reaches 36 months or 300,000 miles of use, Bendix recommends rebuilding the air dryer and the desiccant cartridge.

If the air dryer is particularly dirty, the ADP-IP dryer's metal parts can be easily cleaned using a piece of cloth dipped in mineral spirits or a similar solvent. While cleaning, be sure to look out for signs of severe corrosion, pitting, or cracks. However, take note that superficial rusting or pitting is normal and will not hamper the cartridge's performance.

Buying the Bendix ADP-IP Air Dryer Online

Bendix ADP-IP cartridges have been proven to last up to three years before needing replacement, but if you need one right now you can order them at FinditParts. We offer a comprehensive catalog of genuine Bendix aftermarket parts including the Bendix ADP-IP Air Dryers for various types of air brake systems. Check out our store today to learn more about our great deals and competitive shipping rates.