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Questions and Answers
The air pressure should not drop more than ___ psi single, ___ psi combination during an applied leakage test.
The air pressure should not drop more than ___ psi single, ___ psi combination during an applied leakage test.
3, 4
What is a supply pressure gauge used for?
What is a supply pressure gauge used for?
Guages tell you how much pressure is in the air tanks
The service brake system applies and releases the parking brakes when you use the parking brake control.
The service brake system applies and releases the parking brakes when you use the parking brake control.
False (B)
When air tank pressure rises to around 125 - 130 psi, the governor stops the compressor from pumping air.
When air tank pressure rises to around 125 - 130 psi, the governor stops the compressor from pumping air.
What are the maximum leakage rates for an air brake system?
What are the maximum leakage rates for an air brake system?
The safety relief valve protects the air tanks and the rest of the system from building too much pressure.
The safety relief valve protects the air tanks and the rest of the system from building too much pressure.
How do you test the low pressure warning signal?
How do you test the low pressure warning signal?
The air pressure should not drop more than ___ psi single, ___ psi combination during a static leakage test.
The air pressure should not drop more than ___ psi single, ___ psi combination during a static leakage test.
What are the maximum leakage rates for an air brake system in one minute?
What are the maximum leakage rates for an air brake system in one minute?
A slack adjuster is a lever that connects the brake chamber push rod with the return spring.
A slack adjuster is a lever that connects the brake chamber push rod with the return spring.
The safety valve in an air tank is usually set to open and release air at 150 psi.
The safety valve in an air tank is usually set to open and release air at 150 psi.
Letting up on the brake pedal increases the air pressure and releases the brakes.
Letting up on the brake pedal increases the air pressure and releases the brakes.
Which direction does the S-cam force brake shoes when brakes are applied?
Which direction does the S-cam force brake shoes when brakes are applied?
After applying your brakes fully in a combination vehicle, your maximum air loss in one minute should be no greater than?
After applying your brakes fully in a combination vehicle, your maximum air loss in one minute should be no greater than?
What can legally hold a parking or emergency brake in position for a truck, truck tractor or bus?
What can legally hold a parking or emergency brake in position for a truck, truck tractor or bus?
On S-cam brakes, what happens to the air when you push the brake pedal?
On S-cam brakes, what happens to the air when you push the brake pedal?
Where are foundation brakes found?
Where are foundation brakes found?
Why should you be in the proper gear before starting down a hill?
Why should you be in the proper gear before starting down a hill?
With dual air systems, the air pressure should build from ___ to ___ psi in 45 seconds.
With dual air systems, the air pressure should build from ___ to ___ psi in 45 seconds.
The air compressor governor controls?
The air compressor governor controls?
An air tank is equipped with a drain valve to remove?
An air tank is equipped with a drain valve to remove?
Why does air braking take more time than hydraulic braking?
Why does air braking take more time than hydraulic braking?
What are the two types of air tank drains?
What are the two types of air tank drains?
How often should you check the alcohol evaporator in cold weather?
How often should you check the alcohol evaporator in cold weather?
What happens if you must make an emergency stop?
What happens if you must make an emergency stop?
You should know that your brakes are fading when?
You should know that your brakes are fading when?
Why drain water from the compressed air tanks?
Why drain water from the compressed air tanks?
To check the slack adjusters on S-cam brakes, you should?
To check the slack adjusters on S-cam brakes, you should?
In a combination vehicle, brakes released, the maximum air released is?
In a combination vehicle, brakes released, the maximum air released is?
After applying brakes fully, what is the maximum air loss in one minute for single vehicles?
After applying brakes fully, what is the maximum air loss in one minute for single vehicles?
The brake pedal in an air brake system controls?
The brake pedal in an air brake system controls?
Where will you find the drain valve for each air tank?
Where will you find the drain valve for each air tank?
Compressed air is stored?
Compressed air is stored?
Single vehicle, brakes released: maximum air leakage rate in one minute is?
Single vehicle, brakes released: maximum air leakage rate in one minute is?
What are the three brake systems?
What are the three brake systems?
The emergency brake system uses parts of?
The emergency brake system uses parts of?
A dual air brake system?
A dual air brake system?
An air pressure gauge shows?
An air pressure gauge shows?
What are the three types of low air pressure warning devices?
What are the three types of low air pressure warning devices?
What can you check to see if the spring brakes come on automatically?
What can you check to see if the spring brakes come on automatically?
What are two other names for the brake pedal?
What are two other names for the brake pedal?
The first thing to do when low air pressure warning comes on?
The first thing to do when low air pressure warning comes on?
An emergency brake is required on commercial vehicles, must be held on by mechanical force, could be activated by the loss of air pressure.
An emergency brake is required on commercial vehicles, must be held on by mechanical force, could be activated by the loss of air pressure.
What happens when a brake lining is pushed against the inside of the drum?
What happens when a brake lining is pushed against the inside of the drum?
You should use the parking brake?
You should use the parking brake?
The application pressure gauge shows the driver how much pressure?
The application pressure gauge shows the driver how much pressure?
A fully charged air system typically has?
A fully charged air system typically has?
If oil and water collect in the air tanks, what can happen to the brakes?
If oil and water collect in the air tanks, what can happen to the brakes?
When you put on the brake by pushing down the brake pedal?
When you put on the brake by pushing down the brake pedal?
A wedge brake pushes a wedge between the shoe linings and the drum.
A wedge brake pushes a wedge between the shoe linings and the drum.
What activates a stop light pressure?
What activates a stop light pressure?
To make a smooth safe stop, hold down the clutch while using the brake pedal to control pressure to the brake system.
To make a smooth safe stop, hold down the clutch while using the brake pedal to control pressure to the brake system.
What is the purpose of ABS?
What is the purpose of ABS?
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Study Notes
Air Brake System Basics
- Air pressure should not drop more than 3 psi in single, 4 psi in combination, and 6 psi in a combination of 3 during an applied leakage test.
- Supply pressure gauges indicate the amount of pressure in the air tanks.
- The service brake system does not apply or release parking brakes; this is false.
- The air compressor governor stops pumping air when tank pressure reaches 125-130 psi.
Leakage Rates
- Maximum leakage rates for an air brake system:
- Less than 2 psi for single vehicles and 3 psi for combination vehicles within one minute during tests.
- Static leakage test shows air pressure should not drop more than 2 psi single, 3 psi combination, and 5 psi combination of 3 in one minute.
Safety Mechanisms
- Safety relief valves prevent air tanks from exceeding pressure limits, typically set at 150 psi.
- Low air pressure warning signals should activate before tank pressure drops below 60 psi.
Brake Components and Functionality
- Slack adjusters do not connect the brake chamber push rod to the return spring; this is false.
- The S-cam mechanism forces brake shoes against the drum when brakes are applied.
- Foundation brakes are located at each wheel, crucial for vehicle stopping.
Vehicle Operation and Maintenance
- Proper gear selection before descending a hill allows minimal brake application.
- Dual air systems should build from 85 to 100 psi in 45 seconds.
- Air compressor governors regulate when the compressor pumps air into storage tanks.
Air System Maintenance
- Air tanks must have drain valves to eliminate water and oil, preventing freezing and brake failure in cold conditions.
- Check the alcohol evaporator daily in cold weather to ensure effective brake functionality.
Emergency Procedures
- In an emergency stop, apply brakes firmly to maintain control.
- Brake fading occurs when more pressure is needed to control speed on downgrades.
Air System Operations
- Draining water from compressed air tanks is crucial to prevent brake system issues.
- Brake pedal controls air pressure for braking; it is also referred to as the foot valve or treadle valve.
- The application pressure gauge informs how much pressure is being applied to brakes.
ABS and Safety
- An emergency brake is required on commercial vehicles and must engage mechanically or upon air pressure loss.
- ABS (Anti-lock Braking System) helps maintain vehicle control during emergencies.
Additional Key Facts
- When the brakes are applied, air pressure pushes brake pads against the lining, generating heat to slow the vehicle.
- Spring pressure is legally required to hold the parking or emergency brakes in place for trucks and buses.
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