The compressed air system in a heavy-duty truck is an essential set of components for the braking system, suspensions and a variety of other functions. Maintaining the system correctly will ensure the vehicle is able to stop and go.

Geoff Selby


Every fleet manager knows that water and contaminants (oil and dirt) in the air system can wreak havoc on a vehicle’s operation. Dirty, wet air systems can cause corrosion, increase downtime and, in some rare cases even lead to a crash. Keeping the air clean and dry is a priority in every heavy-duty fleet.


The compressed air system in a heavy-duty truck is an essential set of components for the braking system, suspensions and a variety of other functions. The system should be designed for the vehicle’s specific application and maintained correctly to ensure the vehicle is able to stop as well as it is able to go.


Water, dirt and oil are the enemies of a functional compressed air system on every truck and in every environment, but waste hauling vehicles often operate in extreme driving conditions and in many cases, the compressed air system is under spec’d. In particular, waste hauling vehicles run every day of the year rain, sleet, shine or snow.  On some residential routes, trucks will stop as frequently as every 30 feet, which means the air compressor is running constantly and doesn’t allow the air dryer to cycle. In that kind of environment getting clean, dry air can be nearly impossible and results in underperformance of the entire compressed air system. The resulting wet, dirty air can shorten component lifespan and maintenance intervals as well as increase the total cost of operating the vehicle.


Staying on Top of Air-System Maintenance

Below are a couple of ways fleets can stay on top of their air-system maintenance, improve vehicle uptime and lower overall maintenance costs.


Be Vigilant in Purging Air Tanks

Vehicle air tanks must be purged, at a minimum, on a daily basis. Fleets located in cold weather climates should purge their tanks prior to overnight storage to minimize the chance of ice in the air system.


Vehicles using a lot of air, like residential waste haulers, should consider an automatic drain valve on their tanks. An automatic drain valve will purge the tank periodically throughout the daily operation of the vehicle and thus minimize air contaminants.  It’s important to note, that some valves requires regular maintenance to clean away any dirt or oil that is blocking their exhaust ports.


Consider a Condenser-Separator

A vehicle with an air compressor that is constantly running is a vehicle with an over-worked air dryer. A condenser-separator in-line between the compressor and the air dryer will cool the hot air coming out of the compressor and remove some of the moisture making the air dryer’s job a little easier.


A condenser-separator with a coalescing filter built-in goes one step further by eliminating most of the oil and dirt in the air as well, which will extend the life of the air dryer’s desiccant bed and therefore extend the maintenance interval.


Keep the Truck Rolling

Keeping the trucks on the road—that’s the goal of fleet managers everywhere—and waste haulers face some unique challenges that can make that goal difficult to accomplish. Water and contamination in the air system doesn’t have to be one of them.  Specifying the right equipment and following the best preventive maintenance practices can keep the trucks rolling in any conditions.


Geoff Selby is General Manager at D&D Instruments (Minneapolis, MN) that manufactures the Expello line. He can be reached at (612) 255-1155, e-mail or visit