Air Brake Mock
#1. What does an alcohol evaporator do?
In cold weather, moisture in the air brake system can freeze. Ice in the lines or valves can cause them to stop working. To help prevent this, the air brake system may include an alcohol evaporator. When the air compressor runs, the alcohol evaporator puts alcohol vapor into the air brake system to help prevent water in the lines or valves from freezing. (Alcohol has a lower freezing point than water.) Use only the type of alcohol that is recommended by the evaporator’s manufacturer (typically some form of methanol).
#2. When should you adjust an automatic slack adjuster?
Once properly installed, automatic slack adjusters shouldn’t need manual adjustment. If an automatic slack adjuster strokes beyond the maximum allowed, it usually indicates that there are other brake problems that need to be repaired by a qualified brake service mechanic.
#3. In an air brake system, spring brakes are intended for
Trucks and buses must have parking and emergency brakes in addition to the service brakes. The parking and emergency brakes must be held on by mechanical force (because air pressure can leak away). Spring brakes are usually used to meet these needs.
#4. What is the air brake endorsement for industrial roads called?
An industrial air brake endorsement on your driver’s licence allows you to operate unlicensed vehicles that are equipped with air brakes and are used to transport natural resources on industrial roads. An industrial air brake endorsement is sometimes called an off-highway endorsement
#5. The best way to reduce rough and abrupt braking is to
By maintaining an adequate following distance behind the vehicle in front of you, you make it less likely that you’ll have to brake hard to avoid a collision.
#6. In which of the following situations should a spring parking brake chamber be caged?
If the spring parking brakes have come on because of a loss of air pressure in the braking system, they may have to be released to tow or repair the vehicle. Without air pressure, the only way to release a spring brake is to manually insert a release bolt into the spring brake chamber to release the spring. This is called “caging” the spring
#7. What is an advantage of automatic slack adjusters?
An automatic slack adjuster automatically compensates for normal brake lining wear by adjusting pushrod stroke. Automatic slack adjusters should not normally require manual adjustment of pushrod stroke. However, they still require lubrication at regular intervals.
#8. How can automatic slack adjusters be adjusted?
Once properly installed, automatic slack adjusters shouldn’t need manual adjustment. If an automatic slack adjuster strokes beyond the maximum allowed, this usually indicates that there are other brake problems that need to be repaired by a qualified brake service mechanic. Manual adjustment of automatic slack adjusters is dangerous because it can give a false sense of security about the effectiveness of the braking system.
#9. Minimum governor cut-in pressure is
Pump down to approximately 80 per cent of maximum pressure (for example, if maximum is 125 p.s.i., pump down to 100 p.s.i.). Pause and check that air pressure begins to build (to confirm governor cut-in pressure). In all cases, the governor must cause the compressor to cut in before pressure falls below 80 p.s.i. (552 kPa).
#10. When inspecting the brake chambers, you should check for which of the following?
During your pre-trip inspection, check each brake chamber for cracks, holes, or corrosion. Make sure they are mounted securely. Make sure there are no loose or missing clamps. Make sure that pushrod travel is unobstructed and not excessive.
#11. Which of the following is NOT a part of a truck's braking system?
V-brakes are typically used in bicycles.
#12. The spring brakes will start to apply when the air pressure falls below
If air pressure falls below 414 kPa (60 psi), the spring brakes will begin to apply automatically.
#13. 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.
#14. You're driving a vehicle equipped with a dual air brake system. The low air pressure warning signal comes on, but one system still has normal pressure. What should you do?
Virtually all large commercial vehicles today are equipped with a dual-circuit air brake system for greater safety. A dual air brake system has two separate air brake systems, both controlled by the same set of brake controls. Each system has its own air tanks, hoses, lines, etc. The primary system typically operates the regular brakes on the rear axle or axles. The secondary system operates the regular brakes on the front axle (and possibly one rear axle). If one system loses air pressure, you’ll still be able to stop your vehicle by using the brakes controlled by the other system, but your vehicle’s braking distance will increase, which isn’t good. Better to bring your vehicle to a safe stop and get the brakes repaired.
#15. Minimum governor cut-out pressure is
Governor cut-out pressure should be set somewhere in the range 724–931 kPa (105–135 psi). Usually, it’s 125 psi (862 kPa)
#16. The most common cause of loss of air between the tractor and the trailer is
Glad hand couplers have seals made of rubber or polyurethane, which are designed to prevent air from escaping. Loss of air between the tractor and the trailer is commonly caused by a defective glad hand seal in the service (control) or supply couplers.
#17. What is the "cut-out" level?
The normal pressure range of an air brake system is determined by the pressure levels where the governor turns on the air compressor (cut-in pressure) and turns it off (cut-out pressure). Turning on the compressor is often called “loading the compressor,” and turning off the compressor is often called “unloading the compressor.”
#18. 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.
#19. Maximum governor cut-out pressure is
Governor cut-out pressure should be set somewhere in the range 724–931 kPa (105–135 psi). Usually, it’s 125 psi (862 kPa).
#20. In a trailer with a spring brake priority system, compressed air is supplied to which brakes FIRST?
Trailers with spring brake priority supply compressed air to the spring brakes (to release them) before the service tank has filled.
#21. You're driving a vehicle equipped with air brakes. If the low air pressure warning signal comes on, what should you do?
A low air-pressure warning signal indicates that reservoir air pressures have dropped below 60 psi (414 kPa), which means a serious air brake system safety hazard. Bring your vehicle to a safe stop as soon as possible and try to find the cause of the low pressure. If the air pressure drops much lower, your service brakes may fail completely.
#22. Brakes are designed to withstand temperatures of up to
Brakes are designed to withstand quite a lot of heat. The brake components can withstand temperatures up to about 250° C (482 °F) under hard braking.
#23. There is a split-second delay in activation of _________. There is no delay in activation of _________.
Hydraulic fluid is much less compressible than compressed air. A change to one end of a hose filled with hydraulic fluid instantly affects the other end. Compressed air has to flow through the hose until air pressure at the other end is high enough. For this reason, there can be an air brake lag time of about 0.4 second before the service brakes at the rear of your vehicle start to function. To correct this problem, a separate air tank is usually installed near the rear of the vehicle (closer to the rear brake chambers) along with a relay valve to control when that air is used.
#24. What is the "cut-in" level?
A typical air compressor can produce air pressures of up to 500 psi (over 3,000 kPa), far higher than required for safe operation of the brake system. Therefore, an air compressor governor is employed to keep tank pressures within a relatively narrow range. When tank pressure rises to the “cut-out” level the governor prevents the compressor from pumping more air into the tanks. When the tank pressure falls to the “cut-in” level, the governor allows the compressor to pump air into the tanks again.
#25. What happens to the foot valve when you press down on the brake pedal?
The brake pedal is attached to a valve underneath it, which is called the brake valve or foot valve. When you press the brake pedal, the foot valve opens, allowing air from the service tanks to flow to the brake chambers. The harder you press the brake pedal, the more the valve opens, sending more air to the brake chambers and causing braking force to increase.