Air Brake Test Air Pressure Regulation & Control 2

Question 1

What is the typical 'cut-out' pressure for an air brake compressor governor?

Accepted Answer

125 psi

Answer

The governor cuts out (stops the compressor from pumping) at approximately 125 psi, which is the normal maximum operating pressure for air brake systems.

Question 2

What happens when air pressure drops below the governor 'cut-in' pressure?

Accepted Answer

The compressor begins pumping air back into the system

Answer

When pressure falls to the cut-in level (approximately 100 psi), the governor signals the compressor to start pumping air to rebuild system pressure.

Question 3

What is the purpose of the safety relief valve in an air brake system?

Accepted Answer

To release excess air if the governor fails and pressure becomes dangerously high

Answer

The safety relief valve is a backup protection device that opens to vent air if the governor malfunctions and pressure exceeds a safe limit (usually set at 150 psi).

Question 4

Which component in the air brake system separates oil and moisture from the compressed air before it enters the tanks?

Accepted Answer

The air dryer

Answer

The air dryer removes moisture and oil from the compressed air before it reaches the air tanks, preventing corrosion, freezing, and contamination of the brake system.

Question 5

What does it indicate if the air pressure does not rise from 50 to 90 psi within 3 minutes at engine idle?

Accepted Answer

There is a problem with the air compressor or a significant air leak in the system

Answer

FMCSA requires pressure to build from 50 to 90 psi within 3 minutes at idle, indicating the compressor is working properly; failure to do so signals a compressor or major leak problem.

Air Brake Practice Test Practice Test

Air Brake Practice Test Practice Test

Air Brake Test Air Pressure Regulation & Control 2