Air Brake Systems & Safety Features

What are air brakes? Simply put, air brakes are a type of braking system often used in large vehicles. For example, many trucks, buses, and trains use air brakes. Air brakes utilize compressed air to control braking action, as opposed to hydraulic brakes which use fluid to transmit the force needed to stop a vehicle. Air brakes are known for their reliability and effectiveness in heavy-duty vehicles. They provide a consistent braking performance even with repeated use and are capable of stopping large vehicles safely.

An air brake system includes a few basic components, including an air compressor, air storage tanks, valves, brake chambers and brake shoes or pads. Are you wondering, how air brakes work? Keep reading to find out more.

A vehicle’s air compressor, driven by the engine, pressurizes air and stores it in the air reservoirs. An air reservoir is a storage tank that holds compressed air until it’s needed for braking. The valves in the system control the airflow which, in turn, controls the braking action. The brake valve is the primary valve, operated by the driver to control the engagement of the air brakes, as well as brake release. Brake chambers are found near the wheels of the vehicle and contain diaphragms to convert air pressure into mechanical force. There are two types of brake chambers: service brakes and spring brakes.

Service brakes are used for normal stopping and are driver controlled. When the driver presses down on the brake pedal, the brake valve releases the compressed air into the brake chambers. The diaphragms in the brake chambers move, causing the brake shoes or pads to engage with the wheels This creates friction and slows down the moving vehicle. Releasing the brake pedal allows the compressed air to escape, disengaging the brakes. The vehicle is now able to move once again.Spring brakes are emergency brakes that are held in place by air pressure while driving. If air pressure drops below a certain level, the powerful springs are released and engaged to apply the brakes.

One of the advantages of air brakes is that they can be designed with fail-safe features. In the event of a rupture or disconnection, the spring brakes automatically engage, bringing the vehicle to a stop. Spring brakes act as a backup system and are one of the primary fail-safe features in air brake systems. However, air brakes incorporate several additional fail-safe features to ensure the safety of the braking system in the event of air pressure loss or component failure.

A dual air system, also known as dual circuits, includes two separate air systems operating independently. Each one contains its own air compressor, reservoirs, valves and brake chambers. If one system fails, the other system is still available to provide braking power. Thus ensuring redundancy and increasing the safety of the vehicle.

Pressure protection valves and check valves are used in air brake systems to prevent air pressure loss from affecting the entire system. Pressure protection valves are designed to

monitor and maintain minimum air pressure levels within the system. If the air pressure drops below a certain threshold, pressure protection valves isolate the affected portion of the air brake system. This prevents further loss of pressure and secures enough air pressure for the brakes to function. Check valves allow air to flow in a singular direction and block it from flowing in reverse. If there is a disconnection in one part of the system, check valves to isolate that section. This prevents the loss of air pressure to the rest of the system, allowing the brakes to remain functional even when there is a problem.

Warning devices! A vehicle equipped with air brakes is required to have a low air pressure warning signal. Warning devices built into air brake systems are in place to alert the driver in the case of any issues or abnormalities. Common warning signal indicators are a red light or buzzer. Low air pressure warning system indicators prompt the driver to take immediate action. These warning devices are indicative of psi that is too low. A driver must pay attention to these warnings to help prevent potential brake failure and to address any problems before they compromise the braking system.

These fail-safe features work together in the event of a failure or loss of air pressure, so the air brake system can still provide braking power and bring the vehicle to a safe stop. If you have further questions about air brakes, call us and one of our knowledgeable specialists will be happy to speak with you. Give Busbee’s Trucks and Parts a call today at (803) 564 – 3228 or visit our website,

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