CDL Air Brake - Commercial Driver's License Air Brakes Air Brake System Components Questions and Answers — Questions and Answers
Question 1: What is the primary function of the air compressor governor in an air brake system?
- To cool the compressed air before it enters the air tanks.
- To control when the air compressor pumps air into the storage tanks. (Correct answer)
- To filter oil and water out of the compressed air.
- To regulate the pressure applied to the brakes when the pedal is pressed.
Correct answer: To control when the air compressor pumps air into the storage tanks.
The governor's job is to maintain the air pressure in the air tanks within a specific range. It tells the compressor to start pumping air (cut-in) when the pressure drops to around 100 psi and to stop pumping (cut-out) when it reaches about 125 psi.
Question 2: A driver is operating a vehicle in freezing temperatures. Which component is specifically designed to help prevent ice from forming in the air brake valves?
- Air dryer
- Safety valve
- Alcohol evaporator (Correct answer)
- Slack adjuster
Correct answer: Alcohol evaporator
The alcohol evaporator introduces alcohol vapor into the air system. This vapor mixes with moisture in the air, reducing its freezing point and helping to prevent the formation of ice, which could cause brake failure in cold weather.
Question 3: While monitoring the gauges, a driver notices the application pressure gauge. What information does this specific gauge provide?
- The total amount of air pressure available in the primary and secondary tanks.
- The air pressure required for the spring brakes to engage.
- The amount of air pressure currently being used to apply the brakes. (Correct answer)
- The manufacturer's recommended maximum air pressure for the system.
Correct answer: The amount of air pressure currently being used to apply the brakes.
The application pressure gauge shows how much air pressure is being sent to the brake chambers when the brake pedal is pushed. This indicates how much braking force is being applied.
Question 4: Which of the following components has a safety feature that is typically set to open and release excess air pressure at approximately 150 psi?
- The air compressor governor
- The brake pedal (treadle valve)
- The slack adjuster
- The safety relief valve (Correct answer)
Correct answer: The safety relief valve
The safety relief valve is a crucial safety device installed in the first air tank. It is designed to protect the system from excessive pressure by automatically opening and venting air if the pressure exceeds a preset level, which is typically 150 psi.
Question 5: A driver presses the brake pedal (foot valve or treadle valve). What is the direct action of this component within the air brake system?
- It mechanically forces the brake shoes against the drum.
- It sends a signal to the air compressor to start pumping air.
- It opens a valve that releases compressed air from the storage tanks towards the brake chambers. (Correct answer)
- It drains moisture and oil from the air tanks.
Correct answer: It opens a valve that releases compressed air from the storage tanks towards the brake chambers.
Pushing the brake pedal, also known as the foot valve or treadle valve, opens an internal valve. This allows compressed air to flow from the air storage tanks, through the brake lines, and into the brake chambers to apply the brakes. The harder the pedal is pushed, the more air pressure is applied.
Question 6: What is the main purpose of draining air tanks regularly, especially if the vehicle is not equipped with automatic drain valves?
- To increase the maximum air pressure the system can hold.
- To reduce the overall weight of the vehicle.
- To remove accumulated water and compressor oil, which can cause brake failure. (Correct answer)
- To cool down the air compressor after a long trip.
Correct answer: To remove accumulated water and compressor oil, which can cause brake failure.
Compressed air contains moisture and trace amounts of oil from the compressor. This mixture can accumulate in the air tanks. In cold weather, the water can freeze and block air lines, leading to brake failure. Therefore, it's critical to drain the tanks daily to remove these contaminants.
CDL Air Brake - Commercial Driver's License Air Brakes Air Brake System Components Questions and Answers
What is the primary function of the air compressor governor in an air brake system?