CDL Air Brakes TestAir Brake System PartsMedium
A driver is performing a pre-trip inspection on a commercial vehicle with a dual air brake system. What is the primary function of the check valve between the primary and secondary air tanks?
- ATo allow air to flow in both directions, ensuring equal pressure distribution.
- BTo prevent air from flowing from one tank to the other if a leak occurs in one circuit.
- CTo automatically drain moisture from the air tanks.
- DTo regulate the air pressure going to the front brake chambers.
Show answer & explanationAnswer & explanation
Correct answer: B. To prevent air from flowing from one tank to the other if a leak occurs in one circuit.
In a dual air brake system, check valves are critical safety components. They ensure that if one air tank or circuit develops a leak and loses pressure, the other tank and circuit retain their air pressure, allowing the driver to still have a functional portion of the braking system.
Why the other options are wrong
- A. This describes a non-existent or faulty component; check valves allow flow in one direction only.
- C. Automatic drain valves or manual petcocks are used to drain moisture, not check valves.
- D. The front brake limiting valve regulates pressure to the front brakes, not a check valve between tanks.
Dual Air Brake System Check Valve
A one-way valve located between the primary and secondary air tanks in a dual air brake system, designed to isolate the two circuits.
- Allows air flow in one direction only.
- Protects one circuit if the other fails.
- Ensures partial braking capability remains.
Memory trick: Check Valve Checks Leaks.