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HET4 > Truck/Tractor Air brake review > Flashcards

Truck/Tractor Air brake review Flashcards

1
Q

what components make up the supply circuit

A

compressor - governor - moisture and contamination controls - reservoirs

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2
Q

what are the two cycles of the air compressor

A

loaded and un loaded

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3
Q

during the intake stroke of the loaded cycle of the air compressor what are the inlet and exhaust valves doing

A

exhaust will be closed and the inlet valve will be open

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4
Q

during the compression stroke of the loaded cycle what are the exhaust and inlet valves doing

A

inlet valve will be closed and the exhaust vale will be open

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5
Q

what is the purpose of the governor

A

to control maximum air pressure

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6
Q

what are the three ports on the governor

A

reservoir - unloader - exhaust

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7
Q

what is the purpose of the 25 psi cut in pressure differential in the governor

A

to allow the compressor sufficient time to cool between cut in and out

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8
Q

when will the automatic drain valve purge water and contamination from the reservoir

A

during a drop in system pressure the valve will open ( brake application )

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9
Q

what would a truck operating in cold conditions have in the air system to prevent freeze ups

A

anti freeze injector valve

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10
Q

what should the volume of the air reservoirs be if you were to install a new one on the truck

A

at least 12 times the combined brake chamber volume

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11
Q

what is the purpose of the safety valve

A

to protect the system from excessive air pressure build up in the event that the governor fails to unload the compressor

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12
Q

what would the pressure protection valve setting be in a normal 120 - 130 psi circuit

A

150 psi

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13
Q

CMVSS 121 states the low pressure warning device must be activated at a minimum pressure of

A

60 psi however most systems will come on at 68 - 74 psi

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14
Q

what are the basic components of a primary service circuit

A

dual-circuit brake valve - relay valve - service brake chambers

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15
Q

how is the secondary brake portion of the treadle valve controlled

A

by air pressure in the primary portion of the valve

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16
Q

if the primary portion of the treadle valve was to fail how would the secondary be actuated

A

mechanically by the primary piston

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17
Q

all air brake systems will operate will a certain amount of

A

lag and drag time

18
Q

what is the purpose of the relay valve

A

to speed up application and release time of drive axle service brakes

19
Q

the relay valve will crack the inlet valve open with how much psi

A

2.5 - 8 psi

20
Q

the purpose of the brake chamber is to convert what

A

compressed air into mechanical energy

21
Q

what are the basic components that make up a secondary service circuit

A

dual - circuit brake valve - quick release valve - modulator valves - steer axle service brake chambers

22
Q

what is the purpose of the quick release valve

A

is to speed up the exhaust of air from the service chambers

23
Q

CMVSS 121 states that the parking brake must hold fully loaded air brake equipped vehicles on how much of a grade

A

20%

24
Q

what will happen if the vehicle looses both primary and secondary system air pressure

A

mechanically actuated spring brakes will make an emergency brake application

25
Q

where would the quick release valve be connected in the system

A

between the park control valve and the spring brake chambers

26
Q

where is the anti-compounding double check valve located

A

installed in the parking / emergency brake circuit

27
Q

what is the purpose of the spring brake relay valve

A

to speed up application and release times when spring brakes are being used to back up the primary service circuit

28
Q

what will the spring brake valve have as integral component

A

anti - compounding double check valve

29
Q

what are the two main functions of the spring brake valve

A

to keep the spring brake chamber released during normal operation
to modulate spring brake application pressure if a loss of pressure occurs

30
Q

what are the common components of a tractor brake circuit

A

trailer supply - tractor protection - trailer brake control valve - glad hands - brake light switches

31
Q

what is the tractor protection valve

A

it works in conjunction with the trailer supply valve to provide automatic closure of the trailer service lines

32
Q

what is a ratio valve

A

it can take the place of the quick release valve and also limits brake application pressure to prevent wheel lockup

33
Q

what is a bobtail valve

A

it takes the place of a normal relay valve in the primary circuit . because the truck is not towing a trailer the bobtail valve helps prevent wheel lockup due to the reduced weight of the truck by proportioning the air to the chambers

34
Q

what are the functions of the emergency relay valve

A

. acts as a relay valve to apply, release and regulate braking pressure on the service brakes of the trailer
. provides an emergency function automatically directing full trailer reservoir air pressure to the trailer brake chambers when pressure in the trailer supply line falls below safe operating limits

35
Q

what is dynamiting the trailer brakes

A

when the relay emergency valve makes a full brake application with full trailer reservoir pressure

36
Q

what is the purpose of the trailer spring brake control valve

A

. applies trailer spring brakes in the event of a loss of pressure
. prevents the automatic application of the spring brakes if reservoir air pressure is lost

37
Q

what is the purpose of a pilot relay and single check valve

A

transmits a quick undiminished signal to the towing trailer to reduce lag time

38
Q

what is the purpose of a pressure protection valve

A

maintains pressure in the inlet port regardless of pressure in the outlet port

39
Q

can non charging and charging emergency relay valves be interchanged

A

no

40
Q

what is the function of the trailer release valve ( synchro valve )

A

to block airflow from the dolly supply line to the following trailer until air pressure is high enough to keep the supply valve depressed in the cab

HET4 (31 decks)

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