What is the purpose of an air dryer in an air brake system?

• A. To filter out dirt
• B. To regulate pressure
• C. To remove moisture from compressed air to prevent corrosion and freezing in the brake system.
• D. To lubricate moving parts

Answer: (C)

Moisture in the compressed air is the problem this device tackles. When air is compressed, it carries water vapor. If that moisture isn’t removed, it can condense and freeze in cold lines and valves or rust metal parts inside the brake system. A dry, clean air supply prevents ice in the brake lines and reduces corrosion in reservoirs, valves, and actuators, which keeps the brakes reliable and responsive.

Some systems also filter oil or particulates, but the essential purpose of an air dryer is to remove moisture from the air before it reaches the brakes. Regulating pressure and lubricating parts are handled by other components, not the dryer.