In an air-brake system, the air compressor first takes in air into the storage tanks. Then there is the air compressor governor, which decides the amount of air that should be held within the tank. Drain valves allow air to be let into the air tanks. When the brake pedal is pressed, the air escapes out from the reservoir tanks.
Brake chambers are a jar-shaped entity that moves the vibrating disc. Push rod is made of steel which links the brake area to the slack adjuster which is responsible for maintaining the correct distance between the brake shoes. The brake S-cam rubs the brake shoes against the brake drum. Last but not the least, there is the return spring which is linked to each brake shoe and makes it come back to its normal position when not under pressure from the piston.
Emergency air brakes can be invoked by making use of a button located on the dash. Before one drives an air brake vehicle, the emergency brake button must be turned on to allow air into the system. If the air brake system develops a leak, the pressure would decrease and the emergency brake would get activated. Moreover, heavy vehicles have an added feature, namely, the exhaust break which is also a breaking mechanism that makes use of the engine rather than the air-brake system.
Water has a very undesirable effect on an airbrake system—it prevents air from gaining access to the break mechanism, causing the wheel to get jammed. In fact, this has been a major cause of accidents in vehicles that employ air-brake systems. To counter this problem, the modern air brake systems use drain valves within each air tank. Some systems also include an alcohol evaporator which adds alcohol to the air system. It mainly provides protection in cold weather by breaking down the ice that might accumulate within the system. Air couplers which are made of rubber can also give trouble at times if it develops wear and tear.
Vehicles are also provided with the stop light switch which is meant to warn the drivers behind you. This is a kind of electric switch which is controlled by air pressure. When the air brakes are applied, this light is automatically turned on, thus intimating the vehicles approaching from behind about the driver’s intention to stop.
There is also the low air pressure warning mechanism, which is activated when the air pressure falls below 60 psi. The warning is in the form of a flashing of a red light. A buzzer might also get activated at times. Another form of warning is the wig-wag. In this, a mechanical arm drops down in front of your eyes when pressure exceeds 60 psi. This arm is by default placed in the ‘can’t be viewed’ position by the driver.