1. Air Compressor: A powerful compressor, driven by the engine, continuously builds up compressed air and stores it in large air tanks. These tanks maintain a pressure of around 125 psi (pounds per square inch).
2. Air Pressure Control System: This system regulates the air pressure within the system. It includes components like:
* Pressure Gauge: Shows the air pressure in the tanks.
* Safety Valves: Prevent over-pressurization of the tanks.
* Low Air Pressure Warning System: Alerts the driver if the air pressure drops below a safe operating level.
* Governor: Controls the compressor's operation, turning it off when the tanks reach the desired pressure and turning it on when pressure drops.
* Relay Valves: Control the flow of air to the brake chambers.
3. Brake System: This is where the compressed air does the actual braking:
* Service Brakes (Main Brakes): When the driver depresses the brake pedal, air pressure is released from the brake chambers (located at each wheel). This allows strong return springs to push brake shoes or pads against the drums or rotors, slowing or stopping the truck. The release of air is a crucial element – the brakes are *off* when the system is pressurized.
* Parking Brake (Emergency Brake): A separate system usually uses a spring-applied, air-released mechanism. This means a stored spring applies the brakes, and compressed air is used to release them. If the air pressure fails, the parking brake automatically engages.
* Brake Chambers (Diaphragm Chambers): These are the actuators that convert air pressure into mechanical force. They contain a flexible diaphragm that moves when air pressure changes, pushing a rod that activates the brake mechanism.
4. Air Lines: A network of air lines runs throughout the truck, connecting the compressor, tanks, and brake chambers.
How it works in a dump truck specifically:
The air brake system on a dump truck operates in exactly the same way as described above. The added weight and power of the dump body doesn't change the fundamental mechanism. The larger size and potential for heavier loads might necessitate larger air tanks and potentially more robust components, but the principle remains the same.
Failure Modes:
Because air brakes rely on compressed air, potential failures include:
* Air Leaks: Leaks in the air lines can cause a loss of air pressure and brake failure.
* Compressor Failure: A malfunctioning compressor can't maintain sufficient air pressure.
* Low Air Pressure: This is the most common cause of brake failure and triggers the warning system.
Regular maintenance and inspections are critical for the safe operation of air brakes on any vehicle, especially heavy-duty trucks like dump trucks.
