An air brake system uses compressed air to apply braking pressure to vehicles. It was first developed for use in trains by George Westinghouse in the late 19th century. The key components are an air compressor, reservoir, brake valves, chambers, and lines/hoses. When the brake pedal is pressed, compressed air flows through the lines to push pistons in the chambers, which actuates the brake shoes against the drums to slow the vehicle. Air brakes provide reliable, consistent braking but require more maintenance than hydraulic brakes due to their greater complexity. Regular inspection and maintenance of all components is important for safety.

1. Air Brake System
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2. Introduction to Air Brakes
An air brake 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 or brake shoe 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, such as trucks, buses, trailers, and
semi-trailers, in addition to their use in railroad trains. George Westinghouse first
developed air brakes for use in railway service.He patented a safer air brake on
March 5, 1872. Westinghouse made numerous alterations to improve his air
pressured brake invention, which led to various forms of the automatic brake. In
the early 20th century, after its advantages were proven in railway use, it was
adopted by manufacturers of trucks and heavy road vehicles.

3. Components of an Air Brake System
● Air compressor: Provides compressed air to the system.
● Air reservoir: Stores the compressed air for immediate use.

4. ● Brake Pedal: The brake pedal is the driver's input device to initiate braking. When the driver
presses the pedal, it sends a signal to the brake valves to release the compressed air and apply
the brakes.
● Brake Valves: The brake valve functions as a control valve and directs the pressurized air to the
respective diaphragm to expand it.

5. ● Brake Chambers: Brake chambers are pneumatic devices that convert the compressed air pressure
into mechanical force to actuate the brake shoes or pads. They are mounted on the vehicle's axles.
● Brake Shoes or Pads: These are frictional components that come into contact with the vehicle's
wheels to create friction and slow down or stop the vehicle.

6. ● Slack Adjusters: Slack adjusters are mechanical linkages that adjust the position of the brake shoes
or pads as the brake chambers expand and contract due to changes in air pressure. They ensure
proper clearance and braking performance.
● Brake Drums or Rotors: Brake drums are typically found in drum brake systems, while brake rotors
are used in disc brake systems. These components provide the surface against which the brake
shoes or pads press to create friction and stop the vehicle.

7. ● Brake Lines and Hoses: These convey compressed air from the air reservoirs to the brake chambers.
The lines and hoses need to be durable and properly maintained to prevent air leaks.
● Air Dryer: The air dryer removes moisture and contaminants from the compressed air to prevent
corrosion and freezing in the air brake system.

8. ● Check Valves: Check valves prevent the reverse flow of air within the system, ensuring that air
pressure is maintained and that the brakes can function correctly.
● Warning Devices: Air brake systems include warning devices like pressure gauges and warning lights
to alert the driver if there are issues with the air pressure, such as low air pressure in the system.

9. How Air Brakes Work
● When the driver starts the engine the brake compressor starts as it is
driven by the engine which in turn starts compressing the atmospheric
air and through the compressor governor this compressed air with
optimum pressure is sent to the compressed air reservoir which always
has some amount of air stored from the previous cycle.
● When the driver presses the brake pedal the outlet valve of the triple
valve closes and inlet valve opens up which in turn gives passage to the
compressed air from the reservoir to pass through the brake lines of the
system.
● This compressed air flowing through the brake lines is then transferred
to the brake cylinder which has piston inside it.
● When the compressed air applies pressure over the piston inside the
brake chamber, piston moves away from its original position which
converts this pneumatic energy into the mechanical energy.
● On the wheel end of the brake cylinder, brake drums are placed inside
which there is a housing of the mechanical actuator like springs or slacks
having brake pads at its outer end.
● Due to the movement of piston because of the pressure applied by the
compressed air, The mechanical actuator inside the brake drum expands
which in turn pushes the brake pads in outward direction in order to
make frictional contact with the rotating drum lines.
● With this frictional contact between brake pads and rotating drum lines
brakes are applied to the wheels in order to stop or decelerate the
vehicle.

10. Advantages of Air Brakes
● Reliability: Known for consistent performance.
● Safety: Fail-safe features prevent brake failure.
● Efficient Cooling: Resistant to overheating.
● Consistent Braking: Linear braking force for stability.
● Durability: Longer lifespan and reduced maintenance.
● Adaptability: Suitable for various vehicle types.
● Regulatory Compliance: Required in many regions for heavy vehicles.
● Precise Control: Improved modulation of braking power.
● Reduced Risk of Fluid Leaks: No brake fluid, reducing maintenance and
environmental hazards.

11. Disadvantages of Air Brakes
● Air brake systems are more complex than hydraulic brakes, requiring additional components
like compressors, air tanks, and valves..
● They require regular maintenance by skilled technicians, leading to increased operational
costs.
● Air brake systems are more expensive to manufacture, install, and maintain compared to
hydraulic brakes.
● They rely on a continuous supply of compressed air; any leaks or compressor failures can
lead to brake failure
● Air brakes may have a slightly longer response time in emergency situations.
● Moisture in the system can freeze in cold weather, potentially causing malfunctions.
● Air brakes provide less pedal feedback to the driver, making it harder to judge braking force.
● Air brake components add weight to the vehicle, impacting fuel efficiency and payload
capacity.
● There's a slight delay between pedal action and brake application due to pressure build-up.

12. Maintenance and Inspections
● Daily Pre-Trip Checks: Look for air leaks, loose parts, and visible issues.
● Check for Air Leaks: Listen for hissing sounds, fix leaks promptly.
● Measure Brake Stroke: Ensure brake stroke falls within specified limits.
● Brake Adjustment: Adjust brakes as needed for proper clearance.
● Air Compressor Maintenance: Inspect and maintain the air compressor.
● Inspect Brake Components: Examine components for wear and damage.
● Drain Air Tanks: Remove moisture and contaminants periodically.
● Test Parking Brake: Ensure it holds the vehicle securely.
● Documentation: Maintain records of maintenance and inspections.
● Brake System Testing: Conduct regular brake system tests.
● Training: Train personnel in air brake system maintenance.
● Emergency Brake Test: Verify emergency brake system effectiveness.
● Scheduled Maintenance: Follow the manufacturer's maintenance schedule.
Regular checks and maintenance are crucial for safety and reliability in air brake
systems.

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