Air brakes system was invented by George Westinghouse in 1872. This system is functioning by using compressed air. Air Brakes are used in almost every modern locomotive. In the system of Westinghouse air pressure is used to fill air reservoirs in every wagon. Full air pressure means the brakes are released. Reducing air pressure means the brakes are applied.
Main parts of an Air Brake system are,
1. Brake Pipe
2. Angle Cock
3. Main Reservoir
4. Auxiliary Reservoir
5. Brake Cylinder
6. Drivers’ Brake Valve
8. Triple Valve
9. Feed Valve
Air braking process can be divided into 3 main stages.
- Stage 1: Charging
- Stage 2: Application
- Stage 3: Release
Stage of Charging
In this stage brake pipe has a pressure of 50kPa & it’s distributed to main & auxiliary reservoirs through distributer valve.
Stage of Application
Air pressure in the brake pipes should reduce to apply brakes. This process is done by the driver & when the pressure drops triple valve disconnects the main reservoir while it connects auxiliary reservoir to the brake cylinder. Therefore the pressure in the brake cylinder increases & brakes applied.
Stage of Release
Brake pipe is again charged to a pressure of 50kPa by the compressor. Then the triple valve cuts the connection to the auxiliary reservoir & creates a connection for brake cylinder to the atmosphere. Therefore the brakes are releasing.
There is another part called the Dirt Collector in the brake pipe. Its job is to prevent dust & other particles entering the brake pipe.
Air brakes are quicker & efficient than vacuum brakes. There are some limitations as well. If brakes are applied before the charging stage, a large brake pipe reduction may require. If brake pipe pressure is low than the usual amount, an emergency application of brakes will not effective to stop the train.
Due to some defects in this single pipe system, a two pipe system was introduces. There are 2 pipes in this system, one pipe with a pressure of 5bar & the other with a pressure of 10bar. Here a pipe is continuously charged from the main reservoir. This method helps to overcome pressure loss errors & it reduces the brake releasing time.