CDL Air Brakes TestAir Brake System PartsMedium
A driver is operating an older commercial vehicle not equipped with an air dryer. To prevent air brake system issues in cold weather, which component is crucial for moisture management?
- AThe front brake limiting valve.
- BThe safety valve.
- CThe stop light switch.
- DThe alcohol evaporator.
Show answer & explanationAnswer & explanation
Correct answer: D. The alcohol evaporator.
In older air brake systems without an air dryer, an alcohol evaporator is used to inject alcohol vapor into the air system. This helps prevent moisture from freezing in the air lines and valves during cold weather, which could cause brake system failure.
Why the other options are wrong
- A. The front brake limiting valve reduces air pressure to the front brakes, primarily for steering control, not moisture management.
- B. The safety valve protects against over-pressurization, not moisture freezing.
- C. The stop light switch activates the brake lights when the pedal is pressed, unrelated to moisture management.
Alcohol Evaporator
An alcohol evaporator is a device used in some older air brake systems to inject alcohol vapor into the compressed air, preventing moisture from freezing in air lines and valves during cold weather.
- Used in systems without air dryers.
- Requires daily checking and refilling with methyl alcohol.
- Prevents ice formation that can cause brake failure.
Memory trick: Alcohol keeps the ice at bay.