CDL Combination Vehicles TestCombination Vehicle Air BrakesMedium
A combination vehicle is equipped with a 'one-way check valve' in its air brake system. Where is this valve typically located, and what is its primary function?
- ABetween the air compressor and the wet tank; to prevent air from flowing back to the compressor.
- BBetween the brake pedal and the brake chambers; to prevent air from returning to the pedal.
- CBetween the service line and the emergency line; to ensure equal pressure distribution.
- DIn the spring brake assembly; to allow gradual release of the spring brakes.
Show answer & explanationAnswer & explanation
Correct answer: A. Between the air compressor and the wet tank; to prevent air from flowing back to the compressor.
A one-way check valve is crucial in the air brake system, typically located between the air compressor and the first air tank (wet tank). Its primary function is to prevent compressed air from flowing back into the compressor when it's not running or if there's a problem, maintaining pressure in the reservoirs.
Why the other options are wrong
- B. Air flows from the pedal to the brake chambers; this is not the location or primary function of a one-way check valve in this context.
- C. These lines are for different functions (service brakes vs. emergency/supply) and don't typically have a check valve to equalize pressure between them in this manner.
- D. Spring brakes release when air pressure is supplied; a check valve here would not facilitate gradual release but rather control air flow direction.
One-Way Check Valve (Air System)
A one-way check valve in an air brake system allows compressed air to flow in only one direction, typically from the compressor to the air tanks, preventing backflow and maintaining system pressure.
- Located between compressor and wet tank.
- Prevents air from returning to the compressor.
- Ensures air tank pressure is maintained.
- Critical for system integrity and safety.
Memory trick: Compressor's air, one way it flows, the check valve guards where pressure grows.