Air Brakes Flashcards

Which of the following steps should you use to check the slack adjusters on S Cam brakes?

Answer: Use gloves and pull hard on each slack adjuster

Use gloves and pull hard on each slack adjuster. You should park on level ground and chock the wheels. The parking brakes need to be off so that you can move the slack adjusters. Using gloves, you should pull hard on each slack adjuster. If the slack adjuster moves more than about one inch where the push rod attaches to it, it probably needs adjustment.

What is the typical air pressure of a fully charged air brake system?

Answer: 125 psi

125 psi. A fully charged air system typically has 125 psi of air pressure.

What is the proper way to test the air leakage rate?

Answer: Turn off the engine and release the parking brake

Turn off the engine and release the parking brake. You should test for air leakage with a fully-charged air system. You should turn off the engine, release the parking brake, and time the air pressure drop. The loss rate should be less than two psi in one minute for single vehicles and less than three psi in one minute for combination vehicles.

What is stab braking?

Answer: Applying your brakes until the wheels lock up, releasing, and then reapplying when the wheels start rolling

Applying your brakes until the wheels lock up, releasing, and then reapplying when the wheels start rolling. Controlled braking is applying the brakes as hard as possible without locking the wheels. Both controlled braking and stab braking are effective ways to brake that will keep your vehicle in a straight line and allow you to turn if necessary.

Why do air brakes take longer to stop than hydraulic brakes?

Answer: It takes longer for the air to flow through the lines

It takes longer for the air to flow through the lines. Hydraulic brakes (used on cars and light trucks) work instantly. Air brakes have an added delay because of the time required (about 1/2 second) for the air to flow through the lines.

What will happen if your air compressor stops?

Answer: You'll still have air pressure left in the air tanks to stop

You'll still have air pressure left in the air tanks to stop. If your compressor stops working, you will still have air pressure left in your tanks, but the air compressor will not be able to replace air lost by using your brakes.

How should you check your air compressor governor "cut in" and "cut out" pressures?

Answer: All of the above

All of the above. To check your air compressor governor cut-in and cut-out pressures you should run the engine at a fast idle and monitor the air pressure gauge to see if the air governor cuts out at the manufacturer's specified pressure (typically about 125 psi). With the engine idling, you should step on and off the brake to reduce tank pressure and see if the governor cuts in at the manufacturer's specified pressure (typically about 100 psi).

How fast should the air pressure build in a dual air system?

Answer: From 85 to 100 psi in 45 seconds

From 85 to 100 psi in 45 seconds. In a single air system, the pressure should build from 50 to 90 psi in 3 minutes.

What are the typical air compressor governor cut-in and cut-out pressures?

Answer: Cut-in: 100 psi; Cut-out: 125 psi

The air compressor governor controls when the compressor starts and stops pumping air into the tanks. In most air brake systems, the governor is set to cut-in around 100 psi, meaning the compressor begins to pump air. It then cuts-out around 125 psi, stopping the compressor once the system reaches full pressure to prevent over-pressurization and maintain optimal operating pressure.

What device will keep air in the tanks if the air compressor develops a leak?

Answer: The one way check valve

A one-way check valve is a critical safety component installed between the air compressor and the first air storage tank. Its purpose is to allow compressed air to flow into the tanks but prevent it from flowing back out. This ensures that air pressure is maintained in the brake system's reservoirs, even if the air compressor or its supply line develops a leak.