What is a dual air brake system?

AfricaBoyz Online is dedicated to becoming the continent’s leading online automotive parts supplier whilst also sharing our extensive knowledge of vehicles and the motor industry with all of our customers. In this article, we will discuss and relay all you need to know about dual air brake systems which are fitted in most modern vehicles. Dual air brake systems have been in use since the mid-1970s and the advent of this design has increased road safety significantly as well as potentially saving lives.

WHAT IS A DUAL AIR BRAKE SYSTEM? 

A dual air brake system is effectively two brake systems or circuits combined in one. These air brake systems share a single set of brake controls, whilst each system has its own hoses, air tanks, and lines. One system usually operates the regular brakes on the rear axle/s (typically called the primary reservoir) and the other on the front axle operating the front service brakes (the secondary reservoir).

WHAT IS THE PURPOSE OF A DUAL AIR BRAKE SYSTEM?

The dual air brake system was developed for increased safety and driver controllability purposes in the event of total brake failures.  The concept is to eliminate a total brake failure should there be a fault with any part of the vehicle’s brake components. Should the primary brakes fail for any reason, or if there is an air leak in either system, the secondary system will continue to operate independently, allowing the vehicle to retain its ability to brake. The driver can bring a heavy vehicle to a stop safely. 

WHICH VEHICLES ARE EQUIPPED WITH DUAL AIR BRAKE SYSTEMS?

The majority of vehicles manufactured these days with air brakes and in particular, all heavy-duty vehicles, are equipped with a dual air brake system. In fact, a dual-circuit braking system is a mandated requirement on all heavy-duty vehicles these days.

HOW DO I KNOW IF THE VEHICLE HAS A DUAL AIR BRAKE SYSTEM?

The main visual evidence a driver has that their vehicle is equipped with a dual-circuit brake system is via the dash-mounted air pressure gauges, which are usually marked 'primary' and 'secondary'. Instead of having 2 separate gauges, many vehicles have a single gauge with two needles, indicating the pressure in the primary and secondary systems. All air brake-equipped vehicles will have at least one air pressure gauge mounted on the dashboard so it can be monitored while driving.

HOW DOES THE DUAL AIR BRAKE SYSTEM WORK?

When the brakes of the vehicle are applied, air is drawn from the primary reservoir through the foot valve and is sent to the relay valve, which delivers air from the primary reservoir to the rear brake chambers whilst simultaneously, air is also taken from the secondary reservoir through the foot valve and delivered to the front brake chambers.

BEFORE YOU DRIVE YOUR VEHICLE FITTED WITH A DUAL AIR BRAKE SYSTEM, NOTE THE FOLLOWING

You must allow time for the air compressor to build up in both the primary and the secondary systems prior to driving the vehicle. The pressure should build up to at least 100 psi in both systems before you move the vehicle. 

LOW AIR PRESSURE AND WARNING GAUGES

Both the primary and secondary circuits are equipped with low-pressure warning devices and pressure gauges. If the air pressure drops below 60 psi in either system, it means one of the air systems is low on pressure and that either the front or rear brakes are not operating fully. If the pressure in either or both circuits is too low for normal brake operation, a red warning light will typically come on and an audible buzzer sound. Most vehicles have both of these warning devices.

The low air pressure warning lights and buzzer should shut off when the air pressure in both systems rises to the correct value. This is usually set by the manufacturer’s specifications and is always greater than 60 psi.(414 kPa)

WHEN TO STOP, PULLOVER, AND SAFELY PARK

If the warning devices are activated whilst you are driving, promptly pull over, bring the vehicle to a stop and park safely. Do not continue driving until you have investigated why the warning devices came on and what the cause of the air loss is. Do not continue driving until you can determine the brake system is safe.

If there is a problem, you will need to get the brake system fixed immediately. Should you need any automotive parts, you will be able to source quality parts at affordable prices from AfricaBoyz Online. Our product range is extensive and encompasses a wide selection of parts for all brands and vehicles. Once you have selected your required parts, they will be delivered straight to your doorstep by our trusted courier company and you can get your vehicle up and running in no time.

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