Air Brake System - Parts, How It Works, Diagram, Principle, Benefits | learn mechanical engineering (2023)

table of contents

Air brake components and their functions:

Following are the main parts of an air brake:

1. air compressor

• It is used to increase and maintain air pressure.
• The air compressor's job is to create and maintain the air pressure needed to operate air brakes and air-powered accessories.
• A compressor is designed to pump air into a reservoir, resulting in compressed air.
• The compressor is driven by the vehicle's engine, either by belts and pulleys or shafts and gears.
• The compressor is constantly running with the engine. When the engine is running, the compressor is also running.

2) storage tank

• The tank is used to store the compressed air. Reservoirs are pressure resistant vessels that maintain a supply of compressed air until it is necessary to brake or operate auxiliary air systems.
• They must hold enough air to allow multiple braking if the engine or compressor fails.
• The number and size of reservoirs on a vehicle depends on the number of brake chambers and their size, along with the parking brake setup.

3. Air dryer

• An air dryer can be installed between the compressor and the wet tank to remove moisture from the compressed air.
• It can be partially filled with a highly moisture-absorbent desiccant and an oil filter, or it can be hollow with baffles designed to separate moisture from the air.

4. Safety valve

• A safety valve protects the tanks from overpressurization and explosion if the regulator fails and does not place the compressor in the unload phase.
• The valve consists of a spring-loaded ball that allows air to escape from the reservoir to atmosphere. Valve pressure setting is determined by spring force.

5. Foot valve.

• The foot valve is used to extract compressed air from the reservoirs when needed for braking.
• This pedal operated valve applies air to apply the brakes.
• The driver regulates the amount of air supplied to the brakes depending on how much the foot or brake pedal is applied. When released, air from the service brakes is exhausted through the exhaust port.
• The distance the rider depresses the foot valve pedal determines the air pressure applied, but the maximum application will not exceed the pressure in the reservoir. Releasing the foot valve pedal releases the brakes.

• When the rider applies the brakes by partially depressing the pedal, the foot valve automatically maintains the applied air pressure without the rider having to adjust foot pressure on the pedal.
• When you release the pedal, application air is vented to atmosphere through the exhaust ports. Air pedals are spring loaded and have a different "feel" than hydraulic braking applications.

(v) brake chamber.

• The brake cylinder is used to transfer the compressed air force to the mechanical connections.
• Service brake chambers convert compressed air energy into mechanical energy and motion that apply the vehicle's brakes.
• A brake chamber is a circular container divided in half by a flexible diaphragm.
• The air pressure pushing on the diaphragm causes it to move away from the pressure, pushing the rod against the clearance adjuster.

• The force exerted by this movement depends on the air pressure and the size of the diaphragm. If the diaphragm leaks, air can escape, reducing the effectiveness of the brake actuator.
• A brake cylinder is usually mounted on the axle next to the wheel to be braked.

(vi) Brake assembly

• The brake assembly includes a brake chamber and a backplate mounted slack adjuster for steering action.
• A brake cylinder is usually mounted on the axle next to the wheel to be braked.
• Air pressure is supplied through an inlet port. Air presses against the diaphragm and pressure rod.

• The pushrod is connected via a shackle and pin to a crank-like lever called a "whip adjuster".
• This converts the push from the brake chamber rod into a rotary movement of the brake camshaft and S-cams.
• When the air is depleted, the return spring in the brake chamber returns the diaphragm and rod to the released position.

Disadvantage of air brake system.:

1. If there is a leak in the passage, the whole system will fail. Therefore, sealing the air is very difficult.