Pneumatic braking system: Definition, Principle, Diagram, Construction, Working, Advantages, Disadvantages, Applications [with Pdf]

What is Pneumatic braking System?

The pneumatic braking system is one of the types of Automobile Braking System. It is also known as the Air braking system.

It is Invented by George Westinghouse in the 1860s. In this Braking System, Compressed Air is used the apply the Brake.

The Brake force produce by the Hydraulic Brake is not sufficient to stop the heavy vehicles. Therefore Pneumatic Brake is used in heavy vehicles.

The five Basic components of a Pneumatic or Air brake system are Air Compressor, Storage Tank/Air Reservoir, Brake Valve, Brake Chamber, Brake Drum.

Pneumatic braking system working principle:

Pneumatic Brake uses Compressed Air for actuation of Cam for application of Brake 

Pneumatic braking system diagram:

Pneumatic Braking System diagram
pneumatic-air-braking-system

Construction:

It consists of the following components:-

  1. Air Compressor
  2. Air Filter
  3. Air Dryer
  4. Storage Tank
  5. Safety Valve / Pressure Regulator Valve
  6. Brake Valve
  7. Brake Chamber
  8. Brake Drum
  9. Shoes

1) AIR COMPRESSOR :- Compressor works on the engine power. The compressor takes Air from the atmosphere and conpresses it and sends to the Storage tank.

2) AIR FILTER :- Air Filter is used Before the Compressor to remove the Dust Particals from the Air,  before entering into the Compressor.

3) AIR DRYER :- Air Dryer is used Before the Compressor to remove the Moisture from the Air,  before entering into the Compressor.   Because Moisture damages the Compressor Blades.

4) STORAGE TANK :- It Stores the Compressed Air receives from the Compressor.

5) SAFETY VALVE / PRESSURE REGULATOR VALVE :- This Valve is used on the Storage Tank to maintain the pressure in inside the tank & Removes the excessive air from the tank.

6) BRAKE VALVE :- It is used to Regulate the Air flow from the Storage Tank to Brake Chamber.

It is control by the Brake Pedal. When Driver press the brake pedal, Brake Valve Opens, Therefore Air flows from the Storage Tank to Brake Chamber.

When Driver release the brake pedal, Brake Valve Closes, Therefore Air Stops to flows from the Storage Tank to Brake Chamber.

7) BRAKE CHAMBER :- It is consists of the Diaphragm, Return spring.

The Diaphragm is connected to the push rod & Push Rod is connected to the Lever & Lever is connected to the cam.

When Driver release the brake pedal, Return spring is keeps the diaphragm in original position.

8)  BRAKE DRUM :- It is consists of the Two Brake shoes, Cam, Return spring.

One end of the both shoes hinged & other ends are connected to the Cam. Hence when cam rotates, the brake shoes expands inside the brake drum.

On the outer surface of the brake shoes has friction lining. Therefore when brake shoes expands, Due to friction between shoes & brake drum, Wheel stops.

The shoes are connected with the return spring.  Therefore When driver release the clutch pedal, Shoes are comes to original position due to spring.

How does pneumatic braking system works:-

When Brake apply:-

1) Compressor takes Air from the atmosphere and compresses it and sends to the Storage tank.

2) When Driver Press the Brake Pedal, Brake Valve opens, Therefore flows from the storage tank to the Brake Chamber.

3) In the Brake Chamber, Air applies the Force on Diaphragm, hence Due to this through push rod and adjustable lever, Cam Rotates inside the Brake Drum.

4) Therefore, When cam rotates, the brake shoes expands inside the brake drum & Due to friction between shoes & brake drum, Wheel stops.

When Brake release:-

1) When Driver Release the Brake Pedal, Brake Valve Closes.

2) Hence, Air Stops flowing from storage tank to Brake Chamber.

3) Diaphragm comes to original position & through push rod & Adjustable lever, Cam again Rotates in opposite direction.

Due to Cam movement, Shoes comes to inside. Hence Wheel starts rotating.

Advantages of Pneumatic braking system:

  1. It is Faster in Operation Than Mechanical & Hydraulic Brake.
  2. Less Braking Distance & Braking Time.
  3. It requires less Effort.

Diadvantages of pneumatic braking system:

  1. It is Noisy Operation.
  2. Possibility of Air Leakage, which may results in Braking failure.
  3. It has High Maintenance Cost.

Applications of pneumatic braking system:

It is used in the Heavy-Duty Vehicles, where higher Braking Force requires, Such as follows:-

  1. Trucks
  2. Bus
  3. Air Brake System in Train.

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