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Air Brake Mock

#1. It does not matter if a small amount of oil is discovered during drainage of

Compressors tend to produce a little oil along with the compressed air. The compressed air goes from the compressor to the supply (“wet”) tank, so it’s not surprising to find a little oil in that tank. However, if the amount of oil in the tank increases significantly, it should be checked.

#2. In a vehicle equipped with air brakes, the most common cause of loss of braking power is

The most common cause of loss of braking effort is brakes that are out of adjustment. Federal and provincial laws require you to check manual and automatic slack adjusters daily, during the pre-trip inspection. This includes checking pushrod travel.

#3. What colour is the parking brake control button?

On the dashboard, the parking brake control is a diamond-shaped, yellow, push-pull button. The trailer air supply control is an eight-sided, red, push-pull button.

#4. How do you apply the parking brakes?

The yellow button on the dashboard is the parking brake valve control. Pushing this control in allows air pressure to flow to the spring parking brake chambers, causing the spring parking brakes to release. Pulling this control out exhausts the air pressure against the spring parking brake chambers, causing the parking brakes to apply. Instructions are usually imprinted on the button.

#5. Brake chambers are found on

Each brake is activated by a brake chamber.

#6. What function does the alcohol evaporator perform?

When the air compressor runs, an alcohol evaporator puts alcohol vapor into the air brake system to help prevent water in the lines or valves from freezing. Ice in the lines or valves can cause them to stop working.

#7. What are the main components of a simple, basic air brake system?

The necessary components of the simplest possible air brake system are as follows: (a) a compressor to pump air; (b) a governor to control the compressor; (c) air lines to allow the pressurized air to flow between the air brake system components; (d) a reservoir to store the compressed air; (e) a foot valve that sends compressed air from the reservoir to the brakes when you press the brake pedal; and (f) the foundation brakes, one at each wheel.

#8. If the outer layer of an air line is damaged, but the inner tube is still OK, what should you do?

Air line chafing is a common roadside violation. If you’re pulled over for a roadside inspection, you can be cited for brake line chafing. If the chafing continues, the inner tube may be damaged eventually as well.

#9. A brake lining that has become contaminated with oil or grease indicates a problem with the

A brake lining that has become contaminated with oil or grease indicates a problem with the wheel. For example, oil can leak from a bad wheel seal. As the wheel spins, some of the leaking oil may be splashed onto the brake lining.

#10. To check the brake chambers for leaks, you should

Each air brake chamber with a spring brake is like two chambers in one: the usual service brake chamber and a spring brake chamber attached to the rear of the service brake chamber. To test for leaks, you need to fill both of these with air. To fill the spring brake chambers, release the parking brakes by pulling out the yellow button on the dashboard. To fill the service brake chambers, press and hold the brake pedal. Then listen for the hiss of escaping air and check the rate of air loss

#11. The governor cut-in pressure is normally _________ below the cut-out pressure.

Governor cut-in pressure is normally 20–25 psi below the cut-out pressure.

#12. When you are going at twice the speed, your service brakes will need to work _________ to stop your vehicle.

The kinetic energy of a moving object increases as the square of the object’s speed. Doubling the speed quadruples the kinetic energy (i.e., multiplies it by four). Brakes use friction to convert the kinetic energy of a moving vehicle into heat. Thus, if you double your vehicle’s speed, you’ll need four times as much braking force to bring your vehicle to a complete stop

#13. If the brake chambers on opposite sides of an axle are of different sizes, the result may be

The larger the size of the brake chamber, the greater the force applied to the brake. Thus mismatched brake chambers would apply different braking forces to the wheels on opposite sides of the axle. You should check for mismatched brake chamber sizes during your pre-trip inspection.

#14. When you test the system air-loss rate, the maximum acceptable air-loss rate per minute after the initial drop is ________ except for vehicles with two trailers.

In British Columbia, the maximum acceptable leakage rates per minute are 28 kPa (4 psi) for single vehicles (buses, straight trucks and bobtail tractors) and tractor-trailers with one trailer, and 41 kPa (6 psi) for tractor-trailers with two trailers. If the leakage rate is higher, check for leaks and correct them.

#15. Which of the following is not a part of a braking system?

A leaf spring is part of a vehicle’s suspension. The other choices are components of an S-cam drum brake, a wedge brake, and a disc brake respectively.

#16. After you've connected your tractor to a trailer, you should test the trailer service brakes by applying

After connecting your tractor to the trailer, test the action of the trailer service brakes by applying the hand control valve. This valve applies only the trailer service brakes, not the tractor service brakes. For this reason, the trailer hand valve should not be used for normal braking once your vehicle is on the road.

#17. How can you tell how much air pressure is in the service reservoirs?

The reservoir pressure gauge is connected to the service reservoir. It shows how much air pressure is in the reservoir. In a dual-circuit system, there will be either two gauges, one for each circuit’s service reservoir, or a single gauge with two needles. The gauges are mounted on the instrument panel so you can monitor reservoir air pressures while you drive.

#18. An application pressure gauge shows the air pressure

If your vehicle is so equipped, the application pressure gauge will show how much air pressure you are applying to the brakes. If you have to apply more pressure than before to achieve the same braking effect, it means your brakes are fading (becoming less effective).

#19. The braking system converts the kinetic energy of the moving vehicle into

Brakes use friction to convert the kinetic energy of a moving vehicle into heat. The heat must be dissipated by the brakes before it impairs braking effectiveness (brake fade) or damages the brakes.

#20. Spring-type parking brakes are held in the released position by

Spring brakes contain powerful springs that are normally held back by air pressure. If the pressure drops too low, the spring brakes will automatically kick in.

#21. In an air brake system, what does a governor do?

The governor controls when the air compressor will pump air into the air storage tanks. When air tank pressure rises to the “cut-out” level (around 862 kPa or 125 psi), the governor stops the compressor from pumping air. When the tank pressure falls by about 138 kPa (20 psi) to the “cut-in” pressure, the governor allows the compressor to start pumping again.

#22. When are water-cooled brakes used?

Many vehicles that operate on industrial roads are extremely heavy. Stopping these heavy vehicles puts a lot of pressure on their brakes, which can cause the brakes to overheat. When brakes overheat, the drums expand away from the brake linings, leading to brake fade (loss of braking effectiveness). Some of these vehicles use water directed at the brake drums to help prevent brake drum overheating

#23. For inspecting the air brakes, when should you chock the wheels?

You should chock the wheels whenever the vehicle or a trailer might move on its own and hurt somebody: (1) if the cab will be unoccupied; (2) if you or someone else will be underneath the vehicle (say to inspect the brakes); and (3) when you must perform braking tests that require the brakes to be released; (4) when coupling or uncoupling a trailer.

#24. For large commercial vehicles, which of the following are advantages of air brakes as compared with hydraulic brakes?

For heavy commercial vehicles, air brakes offer significant advantages as compared with hydraulic brakes. Air brakes can apply a much greater force (up to 3,000 pounds) to each foundation brake than hydraulic braking systems can. Air brakes are also more tolerant of slow leaks. If enough hydraulic fluid leaks, you must replenish it before the brakes fail. If compressed air starts to leak, the air compressor can just generate more compressed air. On the other hand, air is much more compressible than hydraulic fluid, which can result in an air brake lag time of up to 0.4 seconds between the time you press the brake pedal and the time that the brakes are fully applied.

#25. Your vehicle's air compressor is belt driven. How do you check for correct belt tension?

To check air compressor belt tension, use your hand to press down on the belt midway between the pulleys. If you can press it down more than double the width of the belt, the tension needs to be adjusted
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