Working Mechanism of Pneumatic or Air Braking System

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The braking system is vital in tractor trailers, trucks, trains, and other industrial machinery equipment. It consists of a pneumatic brake or air brakes, considered a better option than hydraulic fluid-based brakes. The air-powered brakes are preferred in the industrial set-up where heavy machinery trailers and other equipment are used since safety and efficiency are assured. The pneumatic brakes are vital components; thereby, technicians must know the working mechanism of air brakes, their troubleshooting procedure, servicing, and maintenance.

How do air brakes function?

The presence of air brakes or pneumatic brakes in heavy industrial equipment makes things easier and less complex. Pneumatic brakes consist of either disc brakes or drum brakes, or the combination of both brakes. An engine-attached compressor exerts air pressure. This is followed by the air compressor pumping air into the storage tanks, which are believed to store compressed air until it is required.

Air pressure is executed to employ the service brakes and thereby liberate the parking brake. One can find a wide array of air circuits in industrial equipment. When air pressure in the chamber gets released, the parking brake also gets involved. This is because of the spring force initiated in the spring brake chamber. Furthermore, it also enables the parking brake to be used as an emergency brake system.

Operation of drum brakes and disk brakes

Drum brakes: Working mechanism

To understand the working of pneumatic brake or air brake, the working principle of drum brakes and disk brakes is important.

  •   The technician casts down the brake pedal, thereby activating the pneumatic braking system
  •   The air present in the reservoirs gets supplied for the brake valves
  •   The air from the valves reaches the brake chambers
  •   The chambers displace the pushrod to approach the slack adjusters
  •   The slack adjusters apply the pushrod force into the cam rotational force
  •   There is a rotation of the cam, enabling the rollers to rise and also exert force on the shoes against the drum
  •   The equipment slows or stops because of the shoe lining getting in touch with the drum
  •   The technician releases the brake pedal, and the air ejects
  •   The brake shoe and slack adjusters return to the original status, and brakes are released

Disc Brakes: Working Mechanism

The process is marginally different from drum brakes. In this procedure, the technician casts down the brake pedal to activate the pneumatic braking system. The air present in the reservoirs is delivered to the brake valves, which in return is supplied to the brake chambers. Furthermore, the brake chambers activate the caliper that transits force to the inner brake pad.

When the inner brake pad comes into contact with the brake rotor, the caliper slips on the guide pins. This is followed by the brake pad thrusting against the rotor and shifting force to the wheels of heavy machinery tools or equipment. The technician released the brake pedal, which initiates the separation of brake pads from the brake disc, and the brakes are generated.


There are multiple benefits of the pneumatic brake or air brake system. When compared to other braking systems, it is considered to be more effective. The best part about air or pneumatic brakes is that they can be used in multiple accessories in the industrial sector. Understanding drum and disk brakes are vital to know about the concept of pneumatic brakes.



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