You are currently viewing Mastering the Basics: Trailer Air Brake System Diagram Simplified

Mastering the Basics: Trailer Air Brake System Diagram Simplified

What is Air Brake System

Drivers rely heavily on their brakes when hauling thousands of pounds in trucks. The braking device on massive vans, buses, and tractor-trailers consists of air brakes. Trailer Air Brake System Diagram Air-operated brakes are a safer option on larger vehicles as hydraulic fluid can leak and cause an accident.

As a friction brake, an air brake uses compressed air in a piston to apply pressure to the brake pad or brake shoe needed to stop the vehicle. Air brakes are used on large, heavy vehicles, especially those with multiple trailers that need to be connected to the brake system.

In 1872, George Westinghouse developed the first safe air brake for use in railway service. Trailer air brake system diagram He made several modifications to improve the invention of the air-pressure brake, which led to the development of various automatic brakes.

Being an important part of diesel vehicles, you need to know how air brakes work and what the parts are and how to maintain the air brake system. So let’s begin.

Component Trailer air brake system diagram

trailer air brake system

The main components of an air brake system are:

  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

Air filter or dryer

1 Air Compressor

An air compressor helps draw atmospheric air into a storage tank or reservoir. Trailer Air Brake System Diagram It compresses the air to the preferred pressure and transfers it to the storage tank. An air compressor is driven by an engine using a belt drive. A compressor can be air-cooled or cooled by an engine cooling system.

2 Storage tank

The purpose of the storage tank is to safely store the compressed air delivered by the compressor. It is an essential part of the air brake system as the compressed air is responsible for proper operation.

This stores enough air to allow multiple braking when the engine stalls or the compressor fails. Trailer air brake system diagram In a vehicle, the size and number of reservoirs depends on how many brake chambers and their sizes there are, as well as how the parking brake is configured.

3 Brake Pedal

The air brake system is actuated by driver input. The brake pedal is the number one part that activates the brakes to stop or sluggish down the car. It is a type of mechanical coupling that converts input motion into forward motion. Trailer air brake system diagram As a result of pressing the brakes, compressed air is forced into the tire, which stops the vehicle.

4 Brake drum

The brake drum is the only part of the system that performs the braking process. Trailer air brake system diagram When the vehicle stops or slows down, the brake force is transferred to the wheels by the brake drum in the form of friction between the brake pads and the drum lining.

The outer part of the brake drum consists of the drum lining which rotates with the wheel, and the inner part which contains the brake shoe rests when the brake pedal is not depressed. Generally, brake drum is used in air brake system but with proper arrangement.

5 Safety valve

A safety valve is usually installed in the storage tank, near the compressor. A safety valve prevents the storage tank from over-pressurizing as the compressor continues to work to supply air.

It has a spring-loaded ball that allows air to escape from the reservoir to the atmosphere. Trailer air brake system diagram When the air pressure reaches a certain value, the safety valves release the air.

6 Foot Valve

The function of the foot valve can to attract compressed air from the reservoir whilst the brakes can implemented. Trailer air brake system diagram The amount of air supplied to the brakes can controlled by the driver according to the distance to the treadle or brake pedal.

By rotating the foot valve treadle, the actuator controls the amount of air pressure applied, but the maximum pressure must not exceed that in the reservoir.

7 Brake Lining

These can called supply lines. The transfer of compressed air from the reservoir to the brake drum can accomplished by breaking the brake lines that connect the reservoir to the brake drum.

8 Dirt collection

A dirt collector can generally positioned inside the brake line and department pipe. It collects the dust debris separated by way of the air filter. This helps separate dust from the compressed air coming through the brake hose so that only clean air can enter the valve and reservoir.

9 Brake Actuator

A brake actuator is a device consisting of a piston-cylinder arrangement directly connected to the brake pedal. Trailer air brake system diagram When the driver presses the pedal, it applies pressure to the entire assembly.

10 Triple Valve

The triple valve can an important part of the air brake system. It can used to apply and release brakes, which requires a continuous application and release mechanism. It applies pressure as soon as the pedal canĀ  pressed, while releasing pressure immediately after the pedal can released.

11. Air filter and dryer

As the name suggests, air filters remove dust particles from the ambient air, while the dryer input removes moisture and humidity. If the air brake system doesn’t have a dryer, it causes water condensation and air build-up in the lines, and in cold weather that condensed water can cause brake failure.

Manufacture of Air Brake System

The air brake system consists of a two-stage air compressor driven by the crankshaft or gearbox shaft. Trailer Air Brake System Diagram In this braking system, air can drawn from the atmosphere, compressed and then sent to the reservoir through the un-loader valve.

When the reservoir pressure reaches the maximum level, the discharge valve opens to the atmosphere. The compressed air can then discharged directly into the atmosphere.

Each vehicle wheel equipped with a brake chamber has a diaphragm against which air pressure can applied and pushed. This action creates a force that actuates the lever, which activates the cam and applies the brakes. Trailer air brake system diagram There’s an air filter out between the brake valve and the reservoir of every brake chamber, and the chambers can linked to the brake pedal.

Operation of air brake system

The figure above shows the layout diagram of the air brake system. Trailer air brake system diagram These brakes typically include an air filter, bleed valve, air compressor, air reservoir, brake valve, and brake chamber.

Initially, the compressor draws air from the atmosphere through an air filter. The air filter filters the air and delivers it to the compressor, where it can compressed. This compressed air can then be sent to the reservoir through an unloader valve, which opens at a predetermined reservoir pressure and can connected to the brake valve.

From the brake valve, the pipe extends to the front and rear brake chambers. Air can supplied to the brake chambers of each wheel through a brake valve. It can controlled by the driver, who can decide how intense the braking should.

Brake Applied

In the diagram above, air at full system pressure can injected into the brake line connecting the foot valve to the supply reservoir through the dark shading (red). Trailer Air Brake System Diagram The driver does the braking. This can seen by the light shading (pink) on the lines connecting the foot valves to the air chambers.

In the image above, the driver’s foot moves off the brake pedal and releases the brake. As a result, the exhaust port located below the foot valve can opened, allowing air to escape from the brake chambers.

When the brake pedal can released, the return spring returns the master cylinder piston to its original position, there by releasing the pressure. Now, the brake shoe return spring has pressured the brake lining far from the brake drum.

Read More>>>> Hydro pneumatic press working principle

Advantages of Air Brake System

  1. These brakes have an air tank that stores enough energy to stop the vehicle if the compressor fails.
  2. Air brakes are greater powerful than other brakes.
  3. These can be effective even in the event of a leak, so an Trailer air brake system diagram can designed with sufficient capacity to stop the vehicle safely even in the event of a leak.
  4. Brakes require only air to operate, which is readily available.
  5. Compressed air can be used for auxiliary applications not suitable for hydraulics, such as air horns and seat adjusters.
  6. Airline connections are more accessible to connect and disconnect than hydraulic lines.
  7. It provides a greater braking effect as well as better control over the system.
  8. This system has less wear and tear on its parts.
Disadvantages of Air Brake System
  1. Air brakes are generally more expensive than hydraulic brakes.
  2. It compresses the air, resulting in the need for an air dryer to remove moisture, Trailer air brake system diagram making the system expensive and leading to high maintenance and repair costs.
  3. A defective dryer causes ice build-up in an air-brake system in winter.
  4. Air brakes produce noise in the 95-115 dB (decibels) range, with levels closer to 115-120 dB being a normal noise level range and causing immediate hearing damage.
  5. If there is any leakage along the way, the whole system will fail, so it is challenging to seal the air.
  6. Air brakes do not operate underwater and in extreme temperatures.
Use of air brake system
  1. The use of air brakes is necessary in the case of trucks with multiple trailers, Trailer air brake system diagram high-speed long-distance buses, military utility vehicles, and semi-trailers.
  2. George Westinghouse invented the air brake used in trains.
  3. After proving can effectiveness on trains, air brakes were later transferred to heavy vehicles.
  4. They can also used in small vehicles but there is less space for installing air brakes.
  5. There can also be air brakes used for braking buses.


Leave a Reply