Truck owners have two options when it comes to brakes systems: hydraulic or air. While hydraulic systems were once the standard, more operators are choosing air brakes – thanks to their excellent reliability and performance characteristics. Yet, air brake systems do require regular maintenance in order to keep problems at bay.
One particularly important maintenance area involves the component known as the air dryer. Air dryers remove moisture and oil from your air system, thus protecting against corrosion, frozen supply lines, and other serious problems. This article takes a closer look at three key aspects of air dryer maintenance.
1. Cartridge Replacement
Inside of your air dryer is a desiccant-packed cartridge. The hydrophilic beads inside of the cartridge naturally attracts any water vapor in the air passing through the dryer. First, however, a special section of the cartridge also removes any oil. As this reservoir fills up, oil starts to escape into the main chamber containing the desiccant beads.
This oil forms a film on the outside of the beads and reduces their effectiveness at binding up the water. To restore proper functionality, you must replace your cartridge. A cartridge’s lifespan depends on the how you use your vehicle. For buses and other vehicles engaged in constant stopand-start traffic, dryer cartridges only last about 100,000 miles.
As braking demands decrease, air dryer cartridge lifespan increases. For instance, single trailer long-haul trucks may get as much as 300,000 miles out of a dryer cartridge. Trucks that carry two or three trailers, by contrast, must replace their cartridges more frequently – roughly every 200,000 miles.
2. Purge Valve Inspection
Operators should always log their mileage when installing a new air dyer cartridge. Such information allows you to predict roughly when you’ll need to invest in a new cartridge. Yet wise operators don’t simply rely on this information. Instead, they perform periodic visual inspections to ensure that their dryer remains in good working condition.
One of the most important places to look is the outside of your purge valve. The purge valve opens after each compression cycle ends and allows accumulated water to flow out of the air dryer. While light oil deposits on the purge valve don’t pose a serious problem, pay attention for excessive amounts of oil.
Too much oil on the purge valve indicates one of two things. First, if you haven’t been keeping track of your cartridge’s age, that oil probably means it’s time for a replacement. If you replaced your cartridge more recently, excessive oil may mean that it was not installed correctly.
In either case, the large amounts of oil exiting your purge valve probably means your desiccant beads have lost much of their ability to sequester water. As those oil deposits grow thicker, they may also cause problems for the purge valve. Eventually the purge valve may no longer open or close correctly, potentially causing your air dryer to fail altogether.
3. Purge Valve Heater Testing
Historically, air dryer purge valves often experienced problems in winter. Low temperatures caused water to freeze almost instantly as it moved out of the valve, resulting in blockages that rendered the air dryer virtually useless until it thawed out. To keep this problem at bay, most manufacturers now include a build-in purge valve heater to keep water from freezing as it exits the dryer.
Unfortunately, purge valve heaters sometimes fail to work properly – a problem that usually doesn’t manifest until cold weather hits. To keep a bad heater from affecting your truck’s performance, have a professional perform a resistance test periodically. This test evaluates the heater’s electrical system, and provides an easy way to spot problems.
The air dryer has an invaluable role to play in keep your truck’s brakes in good working order. For more information about how to keep the air dryer itself working properly, please contact the truck experts at Godfrey Brake Service & Supply.