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5 Basic Components of an Air Brake System in Trucks

Last Updated: July 2, 2019

If you’re managing a fleet that includes heavy trucks and buses, then you know exactly how much hard work it takes to guarantee that every component of these vehicles is working at optimal capacity. You surely employ a group of great drivers and keep an elite group of mechanics on your roster – perhaps you have even adopted a fleet tracking system to keep track of the movement, service appointments, and important warranty information that applies to these pricey assets. But, just because you’ve taken steps to follow smart hiring practices and invest in automation doesn’t mean that all of your bases are covered.

Components of Air Brake Systems in Trucks

Take the issue of air brake systems, for instance. Most managers and drivers have a general understanding of how these specialized friction brakes work, but not enough fully grasp the true mechanics of this important safety system.  To correct this, take the time to read through our list of the 5 basic components of elementary air brake systems. Remember, the clearer your understanding on this topic, the better informed you will be when forced to make big decisions regarding your fleet.

  1. Air compressor
  2. Reservoirs
  3. Foot valve
  4. Brake chambers
  5. Brake shoes and drums

To get further details on the 5 components of air brake systems in trucks, read on.

1. Air Compressor

An air compressor maintains the proper level of air pressure so that the air brakes and any other air-powered accessories operate safely and consistently.

Depending on the make and model of your heavy truck, its compressor is either gear or belt-driven and gets cooled by either air or an engine cooling system. The compressor(s) startup every time the engine is triggered, and the device loads and unloads air which is pumped in and out of the reservoirs and the other two-cylinder compressors.

Maintenance Tip: If the air compressor’s temperature is governed by an engine cooling system, it may have its own, separate oil supply. If this is the case, ensure that the operator and/or designated fleet team mechanic check the compressor’s oil levels before the truck hits the road. Additionally, many compressors have their own filtration system, which also must be serviced on a regular basis.

2. Reservoirs Basic Components of Air Brake Systems

In the case of heavy truck and bus air brake systems, it’s the reservoirs that hold onto a sufficient amount of compressed air, until the supply is required for braking. Note: drivers cannot control the amount of air that they use when the air brakes are triggered; the amount solely depends on how much has been circulated by the compressor.

In terms of design, reservoirs are pressure-rated tanks that feature special drain valves called draincocks. When the draincocks are in the ‘open’ position, they drain themselves of any moisture or pollutants that might compromise the integrity of the air.

Maintenance Tip: In order to guarantee that your reservoirs are in top shape, each must be drained entirely at least once a day when in service.

3. Foot Valve

The foot valve, otherwise known as the treadle or the brake pedal, is the tool that determines the volume of air pressure used. In this case, the volume is determined by how hard the operator presses their foot on the foot valve.

When the compressed air is released through the brake system, it takes time for it to be produced again through the compressor function (described above). That said, if too much pressure is released in a short period of time, the entire system could fail.

Maintenance Tip: Supply your operators with proper training of the air brake system before they are allowed to join your team. If they are not properly educated on brake maintenance (i.e., they press and release the brakes often and unnecessarily) the air brake system can incur permanent damage.

4. Brake Chambers

Brake chambers, otherwise known as brake pots, are the devices that turn the compressed air into mechanical force. It is through this mechanism that the brakes are triggered and the heavy truck or bus is able to safely halt.

Each one of the brake chambers comes equipped with a specific pushrod stroke adjustment limit. The chamber itself is held together by a clamp assembly that is specially made to regulate the compressed air that is released into the chambers.

Maintenance Tip: Regular maintenance must be performed directly to the brake chambers as dictated by the truck’s manual. This required maintenance is to guarantee that the pushrod stroke is operating within normal range. If this maintenance is not performed, the entire air brake system could fail.

5. Brake Shoes and Drums

By making use of friction, the brake shoes – or pads, depending on the make and model of the truck – are forced outwards, thus initiating the air brake system.

A special brake lining material is attached to the brake shoes to help promote consistency. If the type of lining is a good fit, it should also regulate heat that is created from the friction.

Maintenance Tip: Always replace the aforementioned lining when necessary. Also, make sure that your mechanic frequently services other possible over-worked areas. These issues include distorted drums, poor adjustment, or dirty linings.

Understanding these main components of air brake systems and how to properly maintain them is helpful for preventive maintenance planning and the overall safety of your fleet.

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