The majority of today's air-braked vehicles are now equipped with air dryers. Their role in removing liquid, vapor and solid contaminants from a truck's air system has become increasingly important as components like trailer ABS — which need clean, dry air to function properly-have become more widely used.

Bendix says the trend now is toward a modular dryer and air brake system. Its first modular product, introduced in 1998, was the Dryer Reservoir Module (DRM). With this design, the air dryer was mounted on the end of the air brake reservoir instead of on the vehicle frame. DRM enabled OEs to use valuable space on the frame rail for other equipment.

According to the manufacturer, space is becoming even more of a premium now as OEs must find room on the vehicle for new emissions-specific products, as well as other equipment. Bendix recently introduced the AD-IS, an integrated solution air dryer that combines air system components, giving it the ability to dry air and distribute it as well. There are four separate pressure protection valves in the air dryer housing, which minimizes possible leak points, the company reports. Also, the air dryer's spin-on design allows the desiccant cartridge to be changed in minutes so maintenance is quick and easy.

Another Bendix product is the EverFlow, an air dryer control module designed for use on vehicles with extremely high requirements for air, such as bulk haulers and transit buses. The EverFlow module is comprised of two Bendix soft-seat air dryers. When one is in the charge mode, the other one is in the purge or regeneration mode; every 30 seconds they switch off, so air coming out of the system is always very clean and very dry.

New from Haldex is ModulAIR, a system that consolidates brake circuit functions. Available for heavy truck and bus fleets, it combines air treatment, intelligent control and air distribution in one modular platform. The benefits of reducing the number of components into an integrated air management system, according to the company, include reduced size and weight, extended component life, lower maintenance costs and minimized failure points.

ModulAIR is available with add-on modules and an electronic control unit to provide auxiliary air management functions with in-cab feedback to the driver. Haldex notes the unit's “intelligent” drying cycle system ensures it regenerates only when necessary to reduce power consumption. In high duty-cycle applications, it purges as frequently as necessary to keep air dry.

ModulAIR features the manufacturer's five-stage Multi-Treatment Cartridge (MTC), which also eliminates oil while keeping the air brake system dryer. Haldex's DRYest and PURest air dryer models also feature MTC technology. The DRYest air dryer is designed with multiple integrated elements to provide fleets with low initial-system and lifetime costs, Haldex says. The PURest air dryer utilizes integrated purge volume to eliminate the need for a separate purge tank.

Based on customer feedback, Meritor WABCO says fleet mangers aren't looking for a lot of bells and whistles, but simply good, reliable air dryers, with minimal complexity and maintenance requirements. The company's System Saver air dryers use a spin-on cartridge for easy maintenance. They are lightweight and have a compact design for easy installation in limited spaces.

The line of air dryers from Meritor WABCO includes the System Saver 1200, which features a regeneration system that draws air back from the air brake system. The 1200P uses a separate purge tank. For heavier duty applications, the 1800 and 1800P models have a higher capacity desiccant cartridge. These are ideal for applications calling for frequent starts and stops and long compressor cycles, the company points out. Lastly is the System Saver TWIN air dryer for continuous-flow applications, such as bulk unloading or trucks with central tire inflation systems.

Meritor WABCO says it uses variations in its current product portfolio and application guidelines, along with customer feedback, to ensure vehicles are equipped with the best air dryer for the application. As far as future developments, the manufacturer notes its focus will continue to be on developing new and enhanced products to match customer requirements.


Bendix Commercial Vehicle Systems 310

Haldex Brake Systems Division 311

Meritor WABCO 312