AIR BRAKES

AIR BRAKES

The operation of air brakes is similar to the hydraulic brakes except that in their case compressed air is used to apply brakes instead of hydraulic pressure. Air brakes are commonly used on heavy vehicles, like trucks, buses etc.

The complete layout circuit is shown in Fig. 5.7. The compressor takes air from the atmosphere through the filter and the compressed air is sent to the reservoir through the unloaded valve. The valve gets lifted at a predetermined reservoir pressure (about 900 kPa) and relieves the compressor of load. From the reservoir the air goes to various accessories and to the brake chambers located at each wheel. the control of brake valve is with the driver who can control the intensity of braking according to the requirements. When the brakes are applied, the air pressure in the reservoir decreases. When the pressure drops to 700kPa, the governor again cuts in the compressor to raise system pressure. When air system pressure falls to about 400kPa, a warning in the form of a buzzer, is sounded.

The main components of air brake system are :

1.         Air compressor with air filter to compress atmosphere air.

2.         Unloader valve to maintain a set pressure.

3.         Air reservoir to store compressed air at specified pressure.

4.         Brake valve to control the intensity of braking.

5.         Brake chambers are installed at each wheel to convert air pressure into useful mechanical energy.

5.8.1 Advantages of air brakes

1.         Air brakes are more powerful than mechanical or hydraulic brakes, are exclusively used in heavy vehicles.

2.         The air brake simplifies the chassis design. The components of the system can be located on the chassis any where and are interconnected by a pipe line.

3.         Apart from braking, the compressed air from the reservoir can be used for tyre inflation, windscreen wipers, horns and many other accessories.

5.8.2 Disadvantages of air brakes

1.         Air brakes involve more parts.

2.         Air compressor uses engine power.

References

1. Automobile Engineering (Vol. 1 & 2)            -           K.M.Guptha
2. Automotive Mechanics                                   -           Joseph Heitner
3. Automobile Engineering                                 -           Harbans Singh Reyd
4. Automotive Mechanics                                   -           William H. Course