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Air Brakes Flashcards

Study Test

1
Q

Breaking the emergency (supply) line of a fully charged tractor-trailer unit will result in?

A

Application of the trailer emergency brakes

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2
Q

If an air system failure occurs, you should:

A

Hold a steady application of the service brakes

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3
Q

A cam type brake is correctly adjusted when?

A

Push rod travel is as short as possible without drag

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4
Q

Excessive use of the hand valve (spike brake) on a tractor-trailer unit will result in:

A

Rapid trailer brake wear, possible loss of trailer brakes, and possible jackknife if all vehicle brakes are applied.

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5
Q

Trailers manufactured prior to 1975 were equipped with what type of park brakes?

A

Air park brakes

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6
Q

A tractor-trailer unit with a dual braking system that has experienced an air loss in one of its service circuits:

A

May be safely stopped using air from the intact service circuit

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7
Q

A failure that produces a loss of air pressure in the supply tank:

A

Will prevent air from being replenished in the service reservoirs

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8
Q

A brake response test is performed?

A

To ensure that all the service brakes are operating, and the glad hands are correctly connected

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9
Q

What should the angle be between the slack adjust and push rod when the brakes are fully applied?

A

90° or greater

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10
Q

How can you identify a correctly adjusted brake?

A

Push rod travel is as short as possible without drag

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11
Q

An automatic spring brake application will occur if one of the dual service systems fail?

A

False

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12
Q

When the adjustment screw of the slack adjuster is turned to take up the slack between the brake lining and drum:

A

Push rod travel decreases

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13
Q

A well-adjusted brake:

A

Will have minimum push rod travel with no drag, require less air to make a brake application, and will have less lag time than a poorly adjusted brake.

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14
Q

Vehicles require more power to stop when:

A

Travelling faster, and with more weight (i.e. more momentum)

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15
Q

A service line (blue) failure will result in:

A

A loss of trailer service brakes

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16
Q

If an air brake system air loss is above the allowable limit:

A

The vehicle is not safe to operate

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17
Q

The function of the governor is?

A

To cut the compressor out and in. Cut-out 120-135 psi and Cut-in 95 to 115 PSI (20-25 PSI below the cut-out pressure)

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18
Q

When measuring push rod stroke using the applied service brake method, what should the service brake application pressure be?

A

90-100 PSI

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19
Q

When a vehicle experiences an excessive air loss:

A

Must not be driven on any roadway

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20
Q

If a vehicle experiences an air loss in one of the dual service circuit systems?

A

The corresponding service brakes will not apply

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21
Q

Air tanks must be drained daily to remove moisture and contamination?

A

True

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22
Q

All brake chamber styles have their own adjustment limits?

A

True

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23
Q

The safety valve:

A

Prevents air pressure in the system from exceeding 150 PSI

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24
Q

Trailer spring brakes apply when:

A

The red button is pulled out (i.e. supply valve is closed)

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25
How does a driver know if the anti-lock braking system (ABS) is working?
The dash warning light and trailer ABS light will only turn on during start-up; then turn off.
26
If brakes are out of adjustment:
Spring brakes will not stop or hold the vehicle
27
Most heavy vehicle braking systems are:
Air brakes
28
To check for leaks in an air brake system:
Apply a 100 PSI brake application and check the gauges for leaks. Maximum allowance – 4 PSI for the tractor, plus 2 PSI for each towed unit
29
Air pressure must build from 50-90 PSI with the engine running at 1200 RPM:
In 3 minutes or less
30
Service brake application force depends on;
Service air pressure applied and the area of the diaphragm. Force = Pressure x Area
31
The ability of the braking system will be reduced if:
The load is not evenly distributed
32
The supply line (red):
Fills trailer air tanks and releases the trailer spring brakes
33
A runaway lane should be used when:
When brakes no longer control decent and before the vehicle is out of control
34
Service brake pressure is exhausted from the system:
When the foot brake is released
35
Compressor cut-in pressure is:
95 to 115 psi (20-25 PSI below the cut-out pressure)
36
An inline alcohol injector is used to:
Prevent moisture from freezing
37
Brake chamber force will be greater with:
Increased service brake air pressure, or a larger diaphragm (area). Force = Pressure x Area
38
To prevent vehicles from rolling during brake inspection?
Wheels must be chocked (blocked)
39
Air brakes vs. hydraulic brakes:
Air brakes will respond slower than hydraulic brakes due to lag time, because air needs to flow thru the system
40
When descending a hill in a rural area:
Control the speed of the vehicle from the top of the hill by using engine brake and gearing down, so that you do not need to rely on the service brakes to control your speed
41
When a spring brake is caged (spring manually released with caging bolt):
Spring brakes will not apply
42
When bobtailing (driving a tractor with no trailer):
Increase the following distance from the vehicles in-front of you
43
The park control valve refers to:
The red and yellow buttons on the dash board. (Pull to apply the park brakes, and push to release. The yellow button controls the park and emergency brakes on the tractor and the red button controls the park and emergency brakes on the trailer. Pulling the yellow button will apply the park brakes on both the tractor and trailer “the master valve”)
44
In an air brake vehicle, compressed air is stored in:
Tanks
45
What is the main cause of brake fade?
Overheating the brakes
46
Friction between the brake lining and brake drum creates:
Heat
47
Stopping a heavier vehicle travelling at the same speed as a slower vehicle will:
Require more power and distance to stop
48
What is the most effective way to drain the air tanks?
Open the drain valve fully, and leave the valve open if possible
49
Which air tank must be drained first?
Supply tank (also referred to as the wet tank)
50
If the governor fails to cut-out the compressor, the air pressure will continue to build until the safety valve starts to vent the pressure to atmosphere. At what pressure, will the safety valve prevent the air pressure from exceeding?
150 PSI
51
In an air brake system, the air dryer:
Removes moisture and contamination from entering the system
52
Push rod force is determined by:
Service air pressure applied to the diaphragm. Force = Pressure x Area
53
Pulling the yellow button on the dash will apply:
Tractor and trailer parking brakes
54
A driver should never attempt to service the components of a brake chamber:
True
55
During a pre-trip/brake inspection the vehicle should be securely parked:
On level ground with the wheels chocked
56
If brakes are out of adjustment:
The vehicle must not be driven on the roadway
57
Spring brakes can manually be caged:
When the vehicle is being towed, or for brake service by a mechanic
58
When the low air warning activates, the driver must?
Come to a stop as soon as possible
59
At what pressure does the low air warning activate?
60 PSI or above
60
Glad hand couplers are used to connect air from?
Towing units to trailers
61
Most glad hand couplers are polarized to prevent cross connections?
True
62
Air brake inspections should be done?
At the start of every trip and periodically throughout the shift, and before descending major grades, and at all brake check areas.
63
When the air pressure in the system reaches 60 PSI or below, the spring brakes will:
Begin to drag and apply (emergency brakes)
64
If the trailer service brakes do not work, you can manually apply and release the trailer spring brakes by:
Pushing and pulling the red button
65
Maintaining automatic brake adjustment can be done by:
Applying 100 PSI or more of service air pressure with the park brakes released and with cold drums throughout the day
66
The maximum leak allowed in 2 minutes while pulling 1 trailer is:
6 PSI
67
When braking on a slippery (icy road) without ABS (anti-lock braking system):
Apply steady light pressure on the brake pedal to prevent the wheels from locking up
68
Can brake adjustment be checked without getting out of the truck?
No
69
Pressing the foot brake:
Applies the service brakes
70
Anti-lock braking system (ABS):
Prevent the wheels from locking when braking
71
When braking on a slippery road with an ABS equipped unit you should:
Apply firm and steady pressure on the brake pedal
72
When inspecting the air tanks a driver must check to see?
The tanks are securely mounted and there are no visible cracks.
73
When inspecting drums or rotors?
Check for cracked, broken or missing parts
74
Air pressure from the primary system controls service brakes on the:
Drive axle
75
Disc brake components are:
Clippers and rotors
76
Foundation brake adjustment is required when:
Push rod travel becomes excessive
77
When adjusting a manual slack adjuster:
The S-Cam will rotate in the same direction as it would if the brakes were applied
78
Air brake vehicles must display:
Air pressure in both service tanks (primary and secondary)
79
Parking brakes are applied by:
Mechanical force (springs)
80
If the supply (red) line breaks while driving a tractor-trailer unit?
The trailer spring (emergency) brakes will apply
81
The result of crossing the air lines on a trailer made before 1975 with an empty service reservoir:
Trailer service and emergency brakes will not work
82
Compounding of the brakes will result in some vehicles when?
A full-service brake application is made while the spring brakes are applied
83
2 ways to release the spring brakes:
With air pressure or mechanically caging the brakes
84
In a dual circuit system, which valve prevents air from both the primary and secondary system from dropping during an air leak?
Dual check valve
85
Air delivered thru a dual check valve to spring parking brakes is called?
Blended air
86
Foundation brakes are located:
Every wheel (or set of wheels)
87
In a dual circuit system, service air pressure for the drive axles comes from the primary system and the steering axle from the secondary system?
True
88
What is the advantage of a dual circuit system?
To prevent total brake failure
89
If the compressor discharge line breaks, what prevents a total loss of air?
Check valve
90
If one of the foundation brakes are out of adjustment, what effect will it have on the remaining brakes?
Over-using the remaining brakes, possibly causing overheating
91
The tractor protection valve:
Prevents a loss of service air while bobtailing
92
The red button (trailer supply) is a pressure sensitive button that will pop up if the pressure drops to?
60 PSI
93
Type 20 brake refers to:
20 square inches of diaphragm area

Air Brakes (1 decks)

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