CDL Air Brakes TestInspecting Air Brake SystemsMedium
A driver is conducting a pre-trip inspection and notices moisture, but no oil, consistently being expelled from the air dryer's purge valve. What does this condition primarily suggest?
- AThe air dryer is functioning correctly and removing moisture.
- BThe air dryer's desiccant cartridge is saturated and needs replacement.
- CThe air compressor is injecting excessive oil into the system.
- DThere is a leak in the air dryer's check valve.
Show answer & explanationAnswer & explanation
Correct answer: A. The air dryer is functioning correctly and removing moisture.
The primary function of an air dryer is to remove moisture from the compressed air system. If moisture is consistently being expelled during the purge cycle, it indicates that the air dryer is effectively doing its job by collecting and then expelling water vapor from the air system.
Why the other options are wrong
- B. If the desiccant cartridge were saturated, the air dryer would be unable to remove moisture effectively, and moisture would likely be found in the air tanks downstream, not consistently expelled from the purge valve.
- C. The question specifies 'no oil' is being expelled, so this option is incorrect.
- D. A leak in the check valve would affect air pressure retention or allow backflow, but wouldn't directly explain consistent moisture expulsion as a sign of proper function.
Air Dryer Purge Function
The air dryer removes moisture from the air system and expels it during its purge cycle, typically when the air compressor unloads.
- Removes water vapor from compressed air.
- Purge cycle expels collected moisture.
- Indicates proper operation if moisture is expelled.
Memory trick: Dryer purges water, that's its job, keeping air clean, no glop!