Construction of Air Brake System
The crucial components of an Air Brake System include:
Air Compressor:
The air compressor's pivotal role lies in generating and maintaining the required air pressure. Driven by the vehicle's engine through mechanisms like belts and pulleys or shafts and gears, it pumps air into a reservoir, creating pressurised air. The compressor remains in continuous operation while the engine runs, ensuring a steady supply of compressed air for air brakes and auxiliary systems.
Reservoir:
Reservoirs function as pressure-rated tanks for storing compressed air. They house an ample air volume to accommodate multiple brake applications in scenarios such as engine stops or compressor failures. The number and size of reservoirs vary based on factors like brake chamber count, size, and parking brake configuration.
Air Dryer:
Positioned between the compressor and the wet reservoir, an air dryer aids in moisture removal from the compressed air. It might contain a moisture-absorbent desiccant and oil filter or feature baffles to separate moisture from air.
Safety Valve:
Acting as a safety measure, the valve prevents reservoir over-pressurisation. If the governor malfunctions and fails to unload the compressor, this spring-loaded valve releases excess air into the atmosphere, its pressure setting determined by the spring's force.
Foot Valve:
Fig 2: Foot valve
The foot valve draws compressed air from reservoirs for braking purposes. It's operated by the driver's foot and regulates the air delivered to the brakes based on the degree of treadle or brake pedal depression. Releasing the valve facilitates the movement of the air from the service brakes. The foot valve automatically maintains application air pressure when the brakes are applied partially.
Brake Chamber:
Fig 3: Brake Chamber
Brake chambers serve to convert compressed air pressure into mechanical force, engaging the vehicle's brakes. These circular containers house a flexible diaphragm, with air pressure causing the diaphragm to move and apply force against the slack adjuster. Mounted on the axle near the brake-equipped wheel, brake chambers transfer air pressure into mechanical motion.
Brake Assembly:
Fig 4: Brake Assembly
The brake assembly combines the brake chamber and slack adjuster, connected to the backing plate due to steering dynamics. Air pressure moves through an inlet port, pushing the diaphragm and the pushrod. The pushrod connects to a slack adjuster, which then transforms the motion into a twisting motion for the brake camshaft and S-cams. Upon air exhaustion, the return spring in the brake chamber restores the diaphragm and pushrod to their original positions.
Also, learn about the Mechanical Governor.
