Air Brake (road vehicle)

Air brakes or more formally a compressed air brake system is a type of friction brake for vehicles in which compressed air pressing on a piston is used to apply the pressure to the brake pad needed to stop the vehicle. Air brakes are used in large heavy vehicles, particularly those having multiple trailers which must be linked into the brake system, suchas trucks, buses, trailers, and semi-trailers in addition to their use in railroad trains.

Supply system:-
The air compressor is driven by the engine either by crankshaft pulley via a belt or directly from the engine timing gears. It is lubricated and cooled by the engine lubrication and cooling systems. Compressed air is first routed through a cooling coil and into an air dryer which removes moisture and oil impurities and also may include a pressure regulator, safety valve and a smaller purge reservoir.
Advantages:-
Air brakes are used as an alternative to hydraulic brakes which are used on lighter vehicles such as automobiles.Air brakes have several advantages for large multitrailer vehicles:
1). The supply of air is unlimited, so thebrake system can never run out of its operating fluid, as hydraulic brakes can. Minor leaks do not result in brake failures.
2). Air line couplings are easier to attach and detach than hydraulic lines; there is no danger of letting airinto the hydraulic fluid. So air brake circuits of trailers can be attached and removed easily by operators with no training.
3).Air not only serves as a fluid for transmission of force, but also stores potential energy. So it can serve to control the force applied.
4).Air brake systems include an air tank that stores sufficient energy to stop the vehicle if the compressor fails.
5).Air brakes are effective even with considerable leakage, so an air brake system can be designed with sufficient "fail-safe" capacity to stop the vehicle safely even when leaking.