Air brake system is a type of braking system generally used in heavy commercial vehicles or vehicles which require some really powerful and efficient braking system. It is a kind of friction brake where instead of hydraulic-fluid, air is used as the compression media for brake pads.
Application of air brakes becomes a necessity in case of trucks having multiple trailers, high-speed long-haul buses, vehicles of military utility and semi-trailers. Air brakes were invented by George Westinghouse for use in trains. After having proved its caliber in trains, air brakes were later adapted to be used in heavy vehicles. The safety and braking confidence that air brakes provide to heavy vehicles are vouched for till day.
Working of An Air Brake System-
A typical air brake system configuration for a heavy vehicle consists of service brakes, parking brakes, a control pedal and an air storage tank. Parking breaks in this configuration consist of a set of disc or drum brakes held in lock position by a spring mechanism. Air pressure is then required to release the parking brake and set the vehicle in motion. In case of service brakes which are used for regular operation of the vehicle, a pedal is pushed for stopping or engaging and disengaging the brake.
Generally, a pressure of 6.8 to 8.2 bars is used for this kind of application. A majority of heavy commercial vehicles use drums with air brake systems although now the usage of disc brakes are also catching up. Every vehicle fitted with air brakes has a pressure gauge mounted on the dashboard and in clear line of view of the driver, this enables the driver or the operator of the vehicle to be completely aware of the operational pressure in the compressor. Also, proper systems and safety mechanisms are in place which alerts the driver or operator if there is a malfunction or a sudden drop in operating pressure. As an emergency fail-safe mechanism in case of an extreme sudden drop in the air pressure, the spring operated parking brakes are immediately engaged putting the vehicle to a safe stop.
Watch the video below to understand better-
The basic principle of an air brake system is similar to any other type of braking system, the only differentiating factor being use of compressed air in place of hydraulic fluids. So in principle it’s just a conventional braking system.
Let us now take note of the entire air brake system. An air brake system can be broadly divided into two components: The supply system and The Control System
Supply System: The heart of any air brake system is the compressor, Compressor is the device which generates and in a way regulates the flow of compressed air in the system. The compressor is powered by the engine directly and uses the common lubricant available with the engine.
Compressed air is pushed through a cooling coil and into an air dryer. From here the air is stored in a reservoir tank for use. Reservoir tank is connected with an intricate network of circuits for front brakes, rear brakes, and the parking brakes. The supply system also contains the drain valve, pressure limiting valve, and the safety valve.
Control System: Control system consists broadly of service break circuit, parking brake circuit and the trailer brake circuit (if applicable). Service break circuit consists of two individual break circuits each for front and the rear brake. Both these circuits are connected to their special reservoirs for added safety in case the master reservoir fails.
Parking break circuit is connected to a spring mechanism in which the air pressure is used to keep the spring in unlocked position. A drop in pressure of this circuit results in engaging of parking brakes. The trailer brake system has its own lines for operation and is used when there is a trailer attached to the vehicle. It has a supply line and a control line. The supply line is fed by the master reservoir and control line gets its signal from the service break system for better braking.
Thats the basic crux of an air brake system.