Air Brake Mock
#1. Where is the air dryer located?
The supply (“wet”) tank tends to get most of the moisture because moisture condenses there as the hot air from the compressor cools. To help alleviate this situation, the air dryer dries the air from the compressor before it enters the supply tank. Note: Today’s air dryer technology is so effective that a “wet” tank may not be needed anymore. In a modern Air Dryer Integrated System (ADIS), air from the air dryer goes directly into the primary and secondary service (“dry”) tanks.
#2. 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.”
#3. Which of the following is not a component of a wedge brake?
#4. The foot (treadle) valve
The foot valve is located underneath the brake pedal. When you press the brake pedal, compressed air from the foot valve will flow through the lines and valves of the air brake system. When compressed air reaches the brake chambers, it activates the service brakes.
#5. What maintains normal pressures in the air brake system?
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 (typically about 862 kPa or 125 psi), 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. The cut-in level is typically 138–172 kPa (20–25 psi) below the cut-out level.
#6. 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.
#7. 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.
#8. How often should you inspect your vehicle?
All commercial vehicles that fall under the National Safety Code (NSC) must be inspected before they’re used each day (pre-trip inspections) and at the end of the final trip of each day (post-trip inspections). These inspections are required under the Motor Vehicle Act Regulations. Either you or another person specified by the carrier must perform these inspections.
#9. You’re driving a tractor-trailer. If you’re applying a pressure of 30 psi to the trailer brakes with the foot valve, you can apply a greater pressure at the same time by also using
A two-way check valve allows compressed air from two different sources to flow through the same air line. The valve will select the source with the higher pressure. In this case, the foot valve and hand valve are connected to two-way check valves that in turn lead to the tractor protection valve, and from there to the control (service) line. For example, if the foot valve is sending compressed air at 30 psi (207 kPa) and the hand valve is sending compressed air at 40 psi (276 kPa), then compressed air at 40 psi (276 kPa) will be sent out to the trailer brakes.
#10. If you’re using the applied stroke method during your pre-trip inspection, pushrod travel must not exceed
If you’re using the applied stroke method, you must adjust the brake if pushrod travel is more than 1¾ inches (45 mm)
#11. 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.
#12. When you drain the air tanks, which tank should you drain first?
Always drain the supply (“wet”) tank first to prevent accumulated moisture in the supply tank from passing farther into the system
#13. How many air lines must be connected to a DD3 safety actuator brake chamber?
A DD3 safety actuator brake chamber has three air ports: a service port, an emergency port, and a lock port. The lock port controls when the pushrod is locked in the extended (applied) position.
#14. An alcohol evaporator or air dryer can
In cold weather, moisture that has collected in the supply tank can freeze, and the ice can stop air brake valves from working properly. Two different devices can help alleviate this problem. An air dryer removes much of the moisture from the compressed air before it enters the supply tank. An alcohol evaporator puts alcohol vapour into the air to reduce the likelihood of freezing. (Alcohol has a lower freezing point than water.)
#15. When you’re going to tow a trailer, how can you tell if the trailer’s antilock braking system (ABS) is working?
A trailer has a yellow ABS malfunction lamp on the left (driver’s) side, on either the front or rear corner. It will light up if there’s a problem with the trailer ABS. You should be able to see the lamp in your driver’s-side mirror
#16. In a vehicle equipped with air brakes, what does the governor control?
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 (typically about 862 kPa or 125 psi), 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. The cut-in level is typically 138–172 kPa (20–25 psi) below the cut-out level.
#17. What powers the air compressor?
Air compressors are either powered by an engine belt or (as is more often the case these days) gear driven directly from the engine. Thus the air compressor runs whenever the engine is running.
#18. What does the low air pressure warning device warn you about?
Vehicles with air brakes are equipped with a low air pressure warning device. It will activate a red warning light on the dashboard if air pressure in the primary or secondary air tank has fallen to 414 kPa (60 psi) (although some manufacturers’ systems activate at higher pressures). If this happens, you should brake safely to a stop and repair the problem before the air pressure drops to the point that the service brakes won’t work properly. Note: On older vehicles, a “wig wag” (mechanical arm) may activate instead of a warning light.
#19. The minimum governor cut-in pressure is
The minimum governor cut-in pressure is 552 kPa (80 psi).
#20. Which of the following is an advantage of wedge brakes over S-cam drum brakes?
In a wedge braking system, the brake chamber directly faces the brake drum. Compared with S-cam drum brakes, wedge brakes lack the exposed linkage of the pushrod, clevis pin and external slack adjuster. (Most wedge brakes have internal automatic adjusters.) Today, most commercial vehicles have disc brakes or S-cam drum brakes. However, wedge brakes are still favored for some military and other applications for which the lack of exposed linkage is advantageous on rough, corrosive, or dangerous ground.
#21. Which of the following is the best way to inspect an air compressor?
To check whether the air compressor is properly mounted and secure, you may need to touch it (and its engine belt, if it’s belt driven). The air compressor runs whenever the engine is on. It produces compressed air at a temperature of about 200 °C (about 400 °F). Therefore, it’s safest to turn off the engine so the air compressor and any belts are off as well.
#22. Brake chambers of size 36 are marked with
Typically, the size of a brake chamber is marked as two numbers on the outside of the brake chamber. The first number is the size of the service brake chamber, and the second number is the size of the spring brake chamber. For example, a Type 36/36 brake chamber has a size 36 service brake chamber and a size 36 spring brake chamber.
#23. 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.
#24. 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.
#25. To obtain an air brake endorsement in British Columbia, you must do which of the following?
To obtain an on-highway air brake endorsement in British Columbia, you must meet the following requirements: 1. Complete an air brake course (see the ICBC website for types of courses and their providers). 2. Pass a knowledge test on air brakes. 3. Pass an air brake pre-trip inspection test. 4. Pay the required fees. A road test in a vehicle equipped with air brakes is NOT required. Note: There are two types of air brake courses. If you successfully complete a driver-certification air brake course instead of the standard air brake course, you won’t be required to pass the air brake pre-trip inspection test. [“Air Brake Endorsements,” ICBC, https://www.icbc.com/driver-licensing/types-licences/Pages/Air-brake-endorsements.aspx]
