How Air Brakes Works?

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We all of us are familiar with the brakes and use brakes in our daily life in automobiles. Brake stops or slows down the running part that’s why brake is a necessary component of the automobiles. In automobiles, different types of brakes and their mechanisms are used as per the requirements. The brake types are disc and drum brakes whereas hydraulic and air braking systems are the commonly used mechanisms. Hydraulic and air brake system both have several advantages and disadvantages but here the main concern is on air brake system which is used in heavy automobiles such as buses, trucks and trailers. Air braking mechanism is similar to the hydraulic brake mechanism. In a hydraulic brake system, brake oil is responsible for the whole operation whereas in air brakes compressed air is responsible for the working.   Hydraulic brakes are highly efficient braking system but it has some drawbacks which are removed by the air brakes. Some advantages of air braking system over hydraulic braking system are as follow:

1. A hydraulic brake cannot works on heavy duty applications like trucks and multi-trailers because to stop heavy vehicle large force is required which only obtained by using air brakes. If we use a hydraulic braking system then the size of the hydraulic fluid storage tank and the hydraulic line will increase and require more space in the automobile which is not recommended.

2. In the air brake system, atmospheric air is used as the working substance which is available in abundant so little leakage does not effect on the braking system whereas due to leakage the function of hydraulic breaking system disturb and leads to brake failure.

3. In hydraulic brakes, it is mandatory to maintain the proper amount of braking oil in the reservoir tank but in case of air brakes, nothing is required because atmospheric air is used as a working substance.


Air Brake:

Main components:

1. Air compressor:
Air compressor is the main part of any air brake system it is powered by the engine using belt drives. It compresses the atmospheric air up to the desired pressure and transfers it into the storage tank.

2. Storage tank:
It stores the compressed atmospheric air at high pressure. It is also a necessary part of the air brake system because compressed air is responsible for the whole operation. Breaks can be applied several times during running of an automobile so compressor alone is not able to perform this tasks that’s why air storage reservoir required.

3. Brake pedal:
Brake pedal is the input to the brake mechanism. It is operated by the driver inside the automobile. The brake pedal is kind of mechanical linkage which transfers input motion to the further mechanism and initiate the brake application.

4. Brake actuator:
Brake actuator is the piston-cylinder arrangement which is directly linked with the brake pedal. When the brake pedal is pressed it creates the pressure in the whole assembly.

5. Safety valve:
Safety valve a safety component which is attached to the air storage tank. It prevents the bursting of the tank due to excessive pressure because air compressor works continuously and supplies compressed air into the tank. Air is released by the safety valve when the air pressure reaches a certain value.

6. Air filter and dryer:
Air filter and dryer are the two major components which are used before the air enters into the air compressor. As the name implies air filter is used to remove the dust particle from the atmospheric air whereas dryer removes the moisture and humidity from the inlet air. It is necessary that only dry air enters into the air compressor because moisture content will lead to failure of braking system due to the condensation of the water particles.

7. Dirt collector:
Dirt collector is the small device used before the triplet valve. It is used to collect the dirt particles separated by the air filter.

8. Brake drums:
Brake drum is the parts which execute the brakes. It is the last part of the brake assembly. It is mounted on the tyres of the automobiles.

9. Breaking lines:
Breaking lines are also known as the supply lines. The transfer of compressed air from the reservoir to brake drum is done by breaking lines only.

10. Triple valve:
Triplet valve is responsible for the whole operation in air brakes. To apply and release the brake a continuous apply and releasing mechanism is required which is done by the triple valve. When the brake pedal is pressed it applies the pressure whereas when the pedal is released it releases the pressure immediately.


Working of the air brake system is very simple. With the help of above components, we easily understand the working of the air brake system. The working of air brake system is described in sequence as follow:

1. The working of air brakes starts with the air compressor. It is the main component of the whole system. Air compressor directly powered by the engine. It compresses the atmospheric air and then transfers it into the storage tank.

2. Air firstly passes through the air filter and dryer before entering into the compressor. Air filter removes the dust particles from the air make air pure and dryer removes moisture content from the air.

3. The main working of the braking system starts when the passenger sitting in the vehicle presses the brake pedal, the pedal is directly attached with the actuators having a piston-cylinder arrangement.

4. After pressing the pedal piston compresses the air due to this pressure in the assembly increases. The outlet port of the triplet valve is closed this time and inlet port opens after that compressed air from the reservoir enters into the braking lines.

5. These braking lines directly link with the brake drum which has a piston-cylinder arrangement. As the pressure in the braking lines increases the pistons in the brake drum start moving outwards and apply force on the brake shoes which creates the friction force between the brake shoes and brake drum. This operation stops or slows down the vehicle.

6. To run the vehicle again releases the brake pedal due to this the outlet port of the triplet valve becomes open and inlet ports become close due to this the air is released from the braking line and the brake shoes between the brake drum come again to their initial position with the application of spring.

A brake is the necessity part on any running body. As we learnt about all the components and working of the braking system. The working of the braking systems comes into play in two different ways which are

  • First one is known as service braking which is normal while driving for stop and run the automobile again. It the common application of brakes.
  • The second application of the brake in automobiles is known as parking brakes. In parking brake or handbrake system whole braking system under working until we require to stop the vehicle at a fix position.

This is all about air brakes working. If you have any query regarding this article, ask by commenting. If you like this article, don’t forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.

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