Truck/Tractor Air brake review

Question 1

what components make up the supply circuit

Answer 1

compressor - governor - moisture and contamination controls - reservoirs

Question 2

what are the two cycles of the air compressor

Answer 2

loaded and un loaded

Question 3

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

Answer 3

exhaust will be closed and the inlet valve will be open

Question 4

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

Answer 4

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

Question 5

what is the purpose of the governor

Answer 5

to control maximum air pressure

Question 6

what are the three ports on the governor

Answer 6

reservoir - unloader - exhaust

Question 7

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

Answer 7

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

Question 8

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

Answer 8

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

Question 9

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

Answer 9

anti freeze injector valve

Question 10

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

Answer 10

at least 12 times the combined brake chamber volume

Question 11

what is the purpose of the safety valve

Answer 11

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

Question 12

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

Answer 12

150 psi

Question 13

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

Answer 13

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

Question 14

what are the basic components of a primary service circuit

Answer 14

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

Question 15

how is the secondary brake portion of the treadle valve controlled

Answer 15

by air pressure in the primary portion of the valve

Question 16

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

Answer 16

mechanically by the primary piston

Question 17

all air brake systems will operate will a certain amount of

Answer 17

lag and drag time

Question 18

what is the purpose of the relay valve

Answer 18

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

Question 19

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

Answer 19

2.5 - 8 psi

Question 20

the purpose of the brake chamber is to convert what

Answer 20

compressed air into mechanical energy

Question 21

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

Answer 21

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

Question 22

what is the purpose of the quick release valve

Answer 22

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

Question 23

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

Answer 23

20%

Question 24

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

Answer 24

mechanically actuated spring brakes will make an emergency brake application

Question 25

where would the quick release valve be connected in the system

Answer 25

between the park control valve and the spring brake chambers

Question 26

where is the anti-compounding double check valve located

Answer 26

installed in the parking / emergency brake circuit

Question 27

what is the purpose of the spring brake relay valve

Answer 27

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

Question 28

what will the spring brake valve have as integral component

Answer 28

anti - compounding double check valve

Question 29

what are the two main functions of the spring brake valve

Answer 29

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

Question 30

what are the common components of a tractor brake circuit

Answer 30

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

Question 31

what is the tractor protection valve

Answer 31

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

Question 32

what is a ratio valve

Answer 32

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

Question 33

what is a bobtail valve

Answer 33

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

Question 34

what are the functions of the emergency relay valve

Answer 34

. 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

Question 35

what is dynamiting the trailer brakes

Answer 35

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

Question 36

what is the purpose of the trailer spring brake control valve

Answer 36

. 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

Question 37

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

Answer 37

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

Question 38

what is the purpose of a pressure protection valve

Answer 38

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

Question 39

can non charging and charging emergency relay valves be interchanged

Answer 39

no

Question 40

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

Answer 40

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