Air Brake Systems

The air braking system is a crucial component of modern transportation, providing reliable and efficient braking capabilities for a wide range of vehicles. Whether it’s commercial trucks, buses, trains, or heavy machinery, the air braking system plays a vital role in ensuring safe and controlled deceleration and stopping.

By utilizing compressed air as a force to apply pressure on the brake pads or shoes, the system generates the necessary friction to slow down or halt the vehicle. With its ability to deliver powerful braking performance, the air braking system has become a preferred choice, especially for larger and heavier vehicles that require reliable stopping power and enhanced safety on the road.

Must Read : Hydraulic Brake System

What is air brake system

The air brake system is a type of friction brake used in vehicles that utilises compressed air to generate the necessary force for stopping or slowing down the vehicle.

Note: – It is commonly known as a compressed-air-brake system.

parts of air brake system

These are parts of air brake system work together to convert compressed air into braking force, ensuring effective and reliable stopping power for vehicles.

1. Air compressor
2. Storage tank
3. Brake pedal
4. Brake drum
5. Safety valve
6. Brake lining
7. Dirt collector
8. Brake actuator
9. Triple valve
10. Air filter or dryer

# air compressor

The air compressor is an essential component responsible for supplying compressed air. It draws in air from the surroundings and pressurizes it, storing it in the air reservoirs. This compressed air is then utilized to activate the brake chambers, applying pressure to the brake pads or shoes.Air compressor driven by the engine using a belt drive. A compressor may be air-cooled or cooled by an engine cooling system.

# Storage tank

The storage tank serves as a reservoir for storing compressed air. It is an essential component that holds a sufficient amount of pressurized air to supply the braking system when needed. The storage tank ensures a continuous and reliable source of compressed air, allowing for immediate brake activation and consistent braking performance.

It ensures that there is enough air available to apply the brakes multiple times, even if the engine stops or the compressor fails. The size and number of reservoirs on a vehicle vary depending on factors such as the number and size of brake chambers and the configuration of the parking brake.

# brake pedal

The brake pedal in an air brake system is the foot-operated control that allows the driver to apply the brakes. When the driver presses the brake pedal, it sends a signal to the system, activating the compressed air to flow and engage the brakes. The amount of pressure applied to the brake pedal determines the level of braking force applied to the wheels. The brake pedal is an important interface between the driver and the air brake system, providing precise control over the braking action and ensuring safe and effective vehicle deceleration or stopping.

# brake Drum

It is a circular-shaped metal drum that is attached to the wheel of a vehicle. When the brakes are applied, the brake shoes are pushed against the inner surface of the brake drum, creating friction. This friction between the brake shoes and the brake drum slows down or stops the rotation of the wheel, ultimately bringing the vehicle to a halt. The design of the brake drum allows for effective heat dissipation, preventing overheating and ensuring consistent braking performance.

# Safety valve

In the air brake system, there is a safety valve located near the compressor and storage tank. Its purpose is to prevent the storage tank from becoming too pressurized when the compressor is continuously supplying air. The safety valve is designed with a spring-loaded ball that allows excess air to escape from the tank into the atmosphere. When the air pressure inside the tank reaches certain levels, the safety valve automatically opens and releases the air, ensuring that the pressure stays within safe limits. This helps protect the system from any potential damage or failure caused by excessive pressure.

# brake lining

These are known as supply lines. Transfers of compressed air from the reservoir to the brake drum are accomplished by simply breaking the brake lines that connect the reservoir to the brake drum.

# foot valve

The foot valve which is operated by the driver’s foot. It is typically located on the floor of the vehicle’s driver compartment, near the brake pedal. The foot valve controls the flow of compressed air from the reservoir to the brake chambers when the driver presses the brake pedal. When the driver applies pressure to the brake pedal, the foot valve opens, allowing the compressed air to flow and activate the brakes. Releasing the brake pedal closes the foot valve, cutting off the air supply and releasing the brakes. The foot valve enables the driver to have precise control over the braking system, ensuring safe and effective stopping of the vehicle.

The foot valve’s function is to draw compressed air from the reservoir when the brakes are applied. The amount of air supplied to the brakes is controlled by the driver based on the distance between the treadle and the brake pedal.

# Dirt collector

A dirt collector is a component that is typically installed in the brake line and branch pipe. Its purpose is to gather any dirt particles that have been filtered out by the air filter. By doing so, it ensures that only clean air enters the valve and reservoir by separating the dust from the compressed air flowing through the brake pipe. The dirt collector plays an important role in maintaining the cleanliness and proper functioning of the air brake system, as it prevents any potential contaminants from reaching critical components and causing damage or interference with the brake operation.

# Brake Actuator

The brake actuator is a key component of the air brake system that converts the compressed air pressure into mechanical force to apply the brakes. It is responsible for initiating the braking action when the driver activates the brake pedal.

The brake actuator consists of a diaphragm or a piston mechanism that responds to the air pressure applied by the foot valve. When the driver presses the brake pedal, the air pressure from the foot valve moves the diaphragm or piston, which in turn pushes the brake shoes or brake pads against the brake drum or brake rotor. This creates the necessary friction to slow down or stop the vehicle.

# Triple Valve

The triple valve is a critical component of the air brake system, responsible for controlling the application and release of brakes in response to the driver’s commands ( It applies pressure as soon as the pedal is pressed, while it immediately releases pressure when the pedal is released. It consists of three valves, hence the name “triple valve”: the service valve, the relay valve, and the emergency valve.

The triple valve receives compressed air from the reservoir and distributes it to the brake cylinders. When the driver applies the brake pedal, the service valve opens, allowing air to flow into the brake cylinders and applying the brakes. The relay valve ensures that the brake pressure is maintained, while the emergency valve activates in case of a sudden loss of air pressure, applying the brakes instantly for emergency stops.

# Air Filter and Dryer

The air filter and dryer, responsible for ensuring clean and dry air supply to the system.

The air filter is designed to remove dust, dirt, and other contaminants from the incoming air. It prevents these particles from entering the brake system and causing damage to valves and other sensitive components. By trapping these impurities, the air filter helps maintain the efficiency and longevity of the system.

The air dryer, on the other hand, removes moisture from the compressed air. It prevents water vapor from entering the brake system, which can lead to corrosion, freezing, and reduced braking performance. The air dryer uses desiccants or other drying methods to absorb moisture, ensuring that only dry air flows through the system.

construction of air brake system

The construction of an air brake system includes various components working together to ensure safe and efficient braking in vehicles. The system begins with an air compressor, typically driven by the engine, which supplies compressed air. This compressed air is stored in storage tanks, providing a steady supply for braking operations. Supply lines connect the storage tanks to the brake chambers, enabling the transfer of compressed air.

The brake chambers, located near the wheels, receive the compressed air and convert it into mechanical force. This force is applied to the brake linings, which are attached to the brake shoes. The brake linings make contact with the brake drums, creating friction and slowing down or stopping the vehicle.

The foot valve is a crucial component that allows the driver to control the amount of compressed air supplied to the brakes. It is operated by the brake pedal and regulates the air pressure based on the driver’s input.

Triple valves play a vital role in controlling the air flow within the system. They receive signals from the foot valve and distribute the compressed air to the appropriate brake chambers based on the driver’s commands.

Safety valves are installed to prevent over-pressurization of the system. They release excess air when the pressure reaches certain levels, ensuring the system operates within safe limits.

In addition to these components, control mechanisms such as brake control knobs and levers are used to regulate the overall braking process and provide additional control options for the driver.

working of air brake system

The picture above shows the layout of the air brake system. These brakes have several components, including an air filter, unloading valve, air compressor, air reservoir, brake valve, and brake chamber.

Intially, the compressor pulls in air from the atmosphere through an air filter. The air filter cleans the air and sends it to the compressor for compression. The compressed air then goes to the reservoir through an unloader valve, which opens when the reservoir reaches a certain pressure. The unloader valve is connected to a brake valve.

The brake valve has tubes that extend to the front and rear brake chambers. The brake chambers receive air from the brake valves on each wheel. The driver controls the braking intensity by operating the brake valves.

Brake Applied

In the figure above, the dark shading (red) in the brake line which connecting the supply reservoir to the foot valve directs air at full system pressure. Braking is done by the driver. The light shading (pink) in the lines connecting the foot valves to the air chambers demonstrates this.

As the pedal is depressed, the air is compressed from the reservoir and sent evenly in all directions through the brake valves to further apply the brakes.

In simple language; When the brake pedals are depressed, compressed air from a reservoir is uniformly supplied in all directions to the brake chambers via the brake valve via a pipe that applies the brake.

Brake Released

In the above figure, the driver’s foot is off the brake pedal, releasing the brake. As a result, the exhaust port at the bottom of the foot valve has opened, allowing air to escape from the brake chambers.

As soon as the brake pedal is released by driver, the return spring causes the master cylinder piston to return to its original position, reducing the pressure. Now, the brake shoe return spring has forced the brake lining away from the brake drum.

in simple language ; When the drivers let off of the brake pedals, the master cylinder returns to its original position due to the piston return spring, lowering the pressure. It returns the brake shoes to their original position and releases the brakes.

advantages of air brake system

Some of the advantages of air brake system are :

1. Reliable and Responsive Braking: Air brakes provide reliable and responsive braking performance, allowing for quick and precise stopping of vehicles and machinery. They offer strong braking power and are capable of handling heavy loads effectively.
2. Heat Dissipation: The design of air brakes allows for efficient heat dissipation during braking. As the braking force is applied, the generated heat is dispersed through the air, preventing overheating and ensuring consistent braking performance even during prolonged use.
3. Safety: Air brakes contribute to enhanced safety in vehicles and machinery. Their robust braking power helps prevent accidents by allowing for shorter stopping distances and improved control, especially in heavy-duty applications.
4. Synchronization: In applications where multiple wheels or axles need to be braked simultaneously, such as in trains or large trucks, the air brake system enables synchronized braking. This ensures that all wheels or axles stop simultaneously, promoting stability and reducing the risk of skidding or loss of control.
5. Flexibility and Adjustability: Air brakes offer flexibility and adjustability in terms of brake force. The braking pressure can be easily adjusted to suit different conditions and load requirements, allowing for optimal braking performance in various situations.
6. Resistance to Fading: Air brakes are less prone to brake fade, a phenomenon where the braking effectiveness decreases due to prolonged or repeated braking. This resistance to fading ensures consistent and reliable braking performance over extended periods.
7. Ease of Maintenance: Air brake systems are generally easier to maintain compared to other braking systems. Regular inspections and maintenance tasks, such as checking air pressure and ensuring proper lubrication, help keep the system in optimal working condition.

Overall, the advantages of the air brake system include reliable and responsive braking, efficient heat dissipation, improved safety, synchronization of braking, flexibility in adjusting brake force, resistance to fading, and ease of maintenance. These factors make air brakes a preferred choice.

Disadvantages of air brake System

1. Dependency on Air Supply: Air brakes rely on a continuous supply of compressed air to function properly. Any air leaks or loss of air pressure can significantly affect the braking performance, potentially leading to reduced braking efficiency or complete brake failure. Regular maintenance and monitoring of the air supply system are necessary to prevent such issues.
2. Complex System: Air brake systems can be more complex compared to other braking systems, requiring additional components such as air compressors, valves, reservoirs, and air lines. This complexity can increase the chances of system malfunctions, requiring skilled technicians for troubleshooting and repairs.
3. Response Time: Air brakes may have a slightly longer response time compared to hydraulic or mechanical brakes. The time required for air pressure to build up and actuate the braking mechanism can result in a slight delay in braking, which may be noticeable in certain situations where quick and immediate stopping is necessary.
4. Vulnerability to Moisture and Contaminants: Moisture, dirt, and contaminants can have a negative impact on the performance of air brake systems. Water or oil accumulation within the system can lead to corrosion, reduced air pressure, and compromised braking efficiency. Proper maintenance and regular draining of moisture from the system are essential to prevent these issues.
5. Noise: Air brakes tend to produce more noise during operation compared to other braking systems. The release of compressed air can generate audible sounds, which can be a concern in noise-sensitive environments or for vehicles operating in residential areas.
6. Initial Cost and Complexity of Installation: The initial cost of installing an air brake system can be higher compared to other braking systems, mainly due to the need for additional components and the complexity of the system. This can be a significant factor to consider, especially for smaller vehicles or equipment with lower braking requirements.

application of air brake system

The air brake system is widely used in various vehicles and machinery for effective braking. These are some common applications:

1. Commercial Vehicles: Air brakes are extensively used in large commercial vehicles such as trucks, buses, and trailers. The system provides reliable and efficient braking performance, ensuring the safety of passengers and cargo during transportation.
2. Railway Trains: Air brakes are a vital component of railway train braking systems. Compressed air is used to activate the brakes on each railcar simultaneously, allowing for synchronized and controlled braking across the entire train.
3. Heavy Equipment: Many heavy equipment machines, such as construction equipment, mining trucks, and agricultural machinery, rely on air brakes for their braking needs. The system provides strong and reliable braking power to ensure safe operation in demanding work environments.
4. Industrial Machinery: Air brakes find applications in various industrial machinery and equipment that require precise and efficient braking control. This includes material handling equipment, cranes, elevators, and manufacturing machinery.
5. Emergency Vehicles: Air brakes are often utilized in emergency vehicles like fire trucks and ambulances. The system enables quick and responsive braking, allowing emergency responders to reach their destinations safely and effectively.
6. Recreational Vehicles: Air brakes are also employed in recreational vehicles (RVs) and motorhomes. The system provides enhanced braking performance for larger and heavier recreational vehicles, ensuring safe travels on highways and steep terrains.
7. Off-Road Vehicles: Certain off-road vehicles, such as military vehicles and off-highway trucks, utilize air brake systems. These brakes offer robust stopping power and are designed to withstand challenging off-road conditions.

In summary, the air brake system has a wide range of applications across different sectors, including commercial vehicles, trains, heavy equipment, industrial machinery, emergency vehicles, recreational vehicles, and off-road vehicles. Its reliability, efficiency, and responsive braking performance make it a preferred choice for ensuring safe operations in various transportation and machinery systems.

Source : wikipedia