CDL Combination Vehicles TestCombination Vehicle Air BrakesHard
A combination vehicle's air brake system is equipped with a 'one-way check valve' between the wet tank and the primary/secondary air tanks. What is the primary purpose of this valve?
- ATo prevent air pressure from exceeding safe limits in the wet tank.
- BTo ensure equal air pressure distribution to all brake chambers.
- CTo quickly exhaust air from the primary tank during emergency braking.
- DTo allow air to flow from the wet tank to the other tanks, but not back.
Show answer & explanationAnswer & explanation
Correct answer: D. To allow air to flow from the wet tank to the other tanks, but not back.
The one-way check valve prevents air from flowing back into the wet tank from the primary or secondary tanks. This ensures that if the air compressor or wet tank develops a leak, the primary and secondary (service) air tanks retain pressure, allowing for continued braking capability.
Why the other options are wrong
- A. The safety relief valve prevents over-pressurization, not the check valve.
- B. The brake valves and lines distribute pressure; the check valve's role is pressure retention in service tanks.
- C. The quick release valve or foot valve exhaust air from the brake chambers, not the check valve from the primary tank.
One-Way Check Valve (Air System)
A valve in the air brake system, typically between the wet tank and the primary/secondary tanks, that allows air to flow in one direction only to maintain critical air pressure in the service tanks.
- Ensures air flows from wet tank to service tanks.
- Prevents backflow and pressure loss.
- Crucial for maintaining braking capability if a leak occurs in the compressor or wet tank.
Memory trick: Check valve: one-way street for air, keeps your brakes in repair.