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HET Year 1 > Air Brakes > Flashcards

Air Brakes Flashcards

1
Q

What is coefficient of friction?

A

The coefficient of friction is the amount of force required to move an object divided by the weight of the object

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2
Q

Which of the following refers to the amount of time required to stop a vehicle once the brakes have been applied?

A

Braking time

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3
Q

Result of applying 60 psi air pressure of a type 30 brake chamber?

A

60 x 30 = 1800 lb of force is produced

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4
Q

Cam operated foundation air brakes are non servo because they are mounted to a fixed pin

A

Cam operated foundation air brakes are non servo because they are mounted to a fixed pin

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5
Q

What information is provided through the edge code stamped on a brake block?

A

The friction code of the lining

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6
Q

Why are flat camshafts used on the brake systems of steering axles?

A

Flat cam shafts improve straight line stability during braking

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7
Q

The slack adjuster multiplies the amount of force created at the pushrod

A

The slack adjuster multiplies the amount of force created at the pushrod

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8
Q

Air disc brakes use a return spring to release the brake pad

A

Air disc brakes use a return spring to release the brake pad

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9
Q

Compressors deliver air in the loaded cycle

A

Compressors deliver air in the loaded cycle

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10
Q

-Inlet valve held open by unloaded piston
-Discharge valve closed

What condition is the conpressor in?

A

Compressor is unloaded

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11
Q

What is the purpose of the governor?

A

The governor controls the maximum system pressure in the air brake system

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12
Q

What side of the service brake chamber is always vented to atmospheric air pressure?

A

The pushrod side of the service brake chamber

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13
Q

Brake chamber size is related to the GVW rating of a vehicle

A

Brake chamber size is related to the GVW rating of a vehicle

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14
Q

The quick release valve speeds up the release of the steer axle brakes

A

The quick release valve speeds up the release of the steer axle brakes

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15
Q

Where does the service air pressure present at the inlet port of the quick release valve vent to when the brakes are releasing?

A

The inlet for pressure vents to atmosphere through the dual brake valve exhaust port

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16
Q

What best describes the purpose of the secondary brake circuit?

A

The secondary brake circuit is to allow the operator to control the application and release of the steer axle brakes

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17
Q

What best describes “cracking pressure”?

A

The pressure required to move the relay valve piston down closing the exhaust valve and opening the inlet valve

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18
Q

What best describes the term “differential pressure” in a relay valve?

A

Differential pressure is the difference between the control pressure and the delivery pressure

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19
Q

What is the material which removes the moisture from the air as it moves through the air dryer?

A

Dessicant

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20
Q

Air reservoirs must store a volume of air equal to 12 times the combined volume of the brake chambers on the unit.

A

Air reservoirs must store a volume of air equal to 12 times the combined volume of the brake chambers on the unit.

21
Q

What is the purpose of the single check valve in the air reservoirs?

A

The single check valve ensure the system will have pressure in the event of a reservoir pressure loss.

22
Q

What is the purpose of the safety valve?

A

The safety valve protects the system from excess pressure in the event of governor failure.

23
Q

Flexible hose is used near brake chambers to allow for movement

A

Flexible hose is used near brake chambers to allow for movement

24
Q

What is true about a dual circuit brake valve

A

The primary delivery port is open to the exhaust port in the released position

25
Q

What valve is replaced by the bobtail valve?

A

The standard relay valve

26
Q

A vehicle requires 200 hp to accelerate from 0 to 100 kmh in 60 seconds. If the same vehicle is brought to a complete stop in 6 seconds, the braking system must develope:

A

2000 hp

27
Q

One advantage that air brake systems have is that:

A

The system does not have to be bled when connecting or disconnecting trailers like hydraulic braking systems do

28
Q

If the weight of a vehicle is doubled, the power required to stop the vehicle will:

A

Be doubled

29
Q

If the speed of a moving vehicle is doubled, the power required to stop the vehicle will:

A

Be increased four times

30
Q

If both the speed and weight of a moving vehicle are doubled, the power required to stop the vehicle will:

A

Be increased eight times

31
Q

The term lag time refers to the time required:

A

For the air system to apply the brakes

32
Q

The component of the basic air system that allows the operator to regulate brake application pressure is the:

A

Brake valve

33
Q

Brake lining edge code identifies the lining by:

A

The initials of the manufacturer,
The normal coefficient of friction,
The hot coefficient of friction

34
Q

Using brake lining with a GAWR that is too low can result in:

A

Brake fade

35
Q

The caliper of an air disc brake must be able to slide on its mounting pins so the:

A

Outboard brake pad contacts the brake rotor

36
Q

When an air brake compressor piston is on its compression stroke, the inlet valve:

A

Is closed and the discharge valve is open

37
Q

When the compressor is in its unloaded cycle:

A

The inlet valves are held open

38
Q

The governor controls maximum air system pressure by:

A

Putting the compressor in the unloaded cycle

39
Q

The automatic drain valve drains moisture and contamination from the reservoir when

A

Any drop in reservoir pressure

40
Q

Air brake antifreeze is used in the air brake system to

A

Prevent moisture in the system from freezing

41
Q

Single check valves are installed in the inlet line to both the primary and the secondary service reservoirs because they:

A

Prevent air loss in the event of a failure in the other reservoirs

42
Q

The function of a safety valve is to

A

Limit air pressure build up in the event of a governor failure

43
Q

CMVSS 121 states the minimum pressure at which the low pressure warning devices must warn the operator is:

A

60 psi

44
Q

The function of the relay valve in the primary brake circuit is to speed up the:

A

Application and release of the primary service brakes

45
Q

During normal brake applications, the secondary piston of the dual-circuit brake valve is applied by:

A

Primary service air pressure

46
Q

Air supply for parking/emergency brake operation flows through a double check valve so that the emergency brakes will:

A

Not apply if either service reservoir air pressure is lost

47
Q

The function of the park control valve is to provide manual:

A

And automatic control of all the parking/emergency brakes on the unit

48
Q

A quick release valve is often used in parking/emergency brake Circuits to provide quick:

A

Application of the spring brakes

HET Year 1 (11 decks)

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