Red Seal Truck and Transport Mechanic Practice Exam

What is the primary function of the air dryer in an air brake system?

1. To increase air pressure

2. To remove moisture and contaminants

3. To cool down the compressed air

4. To regulate brake fluid levels

The correct answer is: To remove moisture and contaminants

The primary function of the air dryer in an air brake system is to remove moisture and contaminants from the compressed air. In a typical air brake system, moisture from the atmosphere can enter the system through the compressor. This moisture can cause several issues, including corrosion of the brake components, freezing of water in colder temperatures, and the reduction of the overall efficiency of the brake system. The air dryer utilizes a desiccant material or other filtration methods to absorb or trap moisture and separate particulates from the air before it reaches the brake system. By effectively removing these unwanted elements, the air dryer ensures that the air supplied to the brakes is clean and dry, which is essential for reliable braking performance and the longevity of the components in the air brake system. The other options address functions that are not typically associated with the air dryer. Increasing air pressure relates to the function of the air compressor, cooling compressed air may involve aftercoolers or intercoolers but is not a role of the air dryer, and regulating brake fluid levels pertains more to hydraulic systems than to the air brake system. Thus, the correct answer highlights the crucial role that an air dryer plays in maintaining the integrity and performance of air brake systems.