Air Brake Mock
#1. If the low air pressure warning signal comes on, what should you do?
A low air-pressure warning means there is a serious air brake system safety hazard. Bring your vehicle to a safe stop as soon as possible. If the air pressure drops much lower, your service brakes may fail completely.
#2. At a fast engine idle, the compressor must be capable of building up reservoir pressure from 50 psi to 90 psi in less than
At a fast engine idle (1,000 – 1,200 rpm), the compressor must be capable of building up reservoir pressure from 50 psi to 90 psi in less than three minutes.
#3. Drivers must hold an industrial air brake endorsement if they will be __________ on industrial roads.
Very few drivers require an industrial air brake endorsement. You need an industrial endorsement only if you’ll be operating unlicensed vehicles that are equipped with air brakes and are used to transport natural resources on industrial roads. (An industrial road is any road that exists for the transportation of natural resources, machinery, materials or personnel. Industrial roads include all company bridges, wharves and log dumps.) You don’t need an industrial air brake endorsement to operate skidders, loaders, graders or yarders on industrial roads.
#4. Normally, who can adjust automatic slack adjusters?
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. Don’t attempt to adjust an automatic slack adjuster except in an emergency in which your brakes have failed on the road
#5. The air compressor should be inspected only when
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.
#6. 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.
#7. Where are the air brake chambers located?
There is a brake chamber at each brake. The brake chamber converts the pressure of compressed air into mechanical force to operate the brake
#8. You may be fined as much as _______ for driving a vehicle whose brakes are out of adjustment.
You may be fined as much as $2,000 for driving a vehicle with defective brakes. This includes brakes with excessive brake chamber pushrod stroke.
#9. 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
#10. 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.
#11. 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.
#12. 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.
#13. Which of the following is a part of a disc brake?
In a disc brake, a caliper forces two brake pads against the disc (also known as a rotor). The resulting friction slows the wheel.
#14. 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.
#15. While travelling downhill, you notice that each time you want to brake, you must press the brake pedal farther down than the last time to achieve the same braking force. What could be causing this?
Brake fade is the reduction in braking effectiveness that can occur after repeated or continuous application of the brakes. You may find that you have to press the brake pedal farther down to achieve the same amount of braking force that you did before.
#16. Should you pump (keep pressing and releasing) air brakes?
Each time you release the brakes, some compressed air leaves the system and must be replenished by the air compressor. If you keep pressing and releasing the brake pedal, air may leave the system faster than the air compressor can replenish it. The air pressure may drop to the point that the low air pressure warning signal will come on.
#17. Air pressure must rise _____________ with the engine idling at 600–900 rpm within 2 minutes.
To test the air pressure build-up time, start by reducing the pressure to below 552 kPa (80 psi). If the vehicle has a trailer attached, ensure the trailer supply valve is closed (pulled out). With the engine idling at 600–900 rpm, the air pressure must rise from 587 kPa (85 psi) to 690 kPa (100 psi) within two minutes.
#18. If 40 psi of pressure is applied to a brake chamber diaphragm of 30 square inches, the maximum force exerted would be
“Psi” stands for “pounds per square inch”: the force in pounds that is applied to each square inch. In this case, the pressure is 40 pounds per square inch, which is applied to an area of 30 square inches. Hence, 40 pounds per square inch × 30 square inches = 1,200 pounds
#19. If air is lost in one circuit of a tractor-trailer's dual-circuit system but the compressor and governor are still working properly,
A dual air brake system has two separate air brake circuits, both controlled by the same set of brake controls. Each circuit has its own air tanks, hoses, lines, etc. The primary circuit typically operates the regular brakes on the rear axle or axles. The secondary circuit operates the regular brakes on the front axle (and possibly one rear axle). If one circuit loses air pressure, the other circuit should still work as long as the compressor and governor are still working properly.
#20. 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.
#21. 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.
#22. Which tank is likely to collect the most moisture?
Hot compressed air from the air compressor goes first to the supply tank. It’s also called a “wet” tank because as the compressed air cools, moisture tends to condense in the tank. When air leaves the supply tank, it splits into two circuits, passing into the primary and secondary air tanks. These tanks are also called “dry” tanks because they collect less moisture than the supply or “wet” tank.
#23. 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.
#24. Wedge brakes are designed to be
Wedge air brakes are designed to be self adjusting. Wedge brakes have internal automatic adjusters.
#25. What are the service brakes used for?
When you press the brake pedal in normal driving, it’s the service brake system that applies the brakes.