Truck/Tractor Air brake review Flashcards
what components make up the supply circuit
compressor - governor - moisture and contamination controls - reservoirs
what are the two cycles of the air compressor
loaded and un loaded
during the intake stroke of the loaded cycle of the air compressor what are the inlet and exhaust valves doing
exhaust will be closed and the inlet valve will be open
during the compression stroke of the loaded cycle what are the exhaust and inlet valves doing
inlet valve will be closed and the exhaust vale will be open
what is the purpose of the governor
to control maximum air pressure
what are the three ports on the governor
reservoir - unloader - exhaust
what is the purpose of the 25 psi cut in pressure differential in the governor
to allow the compressor sufficient time to cool between cut in and out
when will the automatic drain valve purge water and contamination from the reservoir
during a drop in system pressure the valve will open ( brake application )
what would a truck operating in cold conditions have in the air system to prevent freeze ups
anti freeze injector valve
what should the volume of the air reservoirs be if you were to install a new one on the truck
at least 12 times the combined brake chamber volume
what is the purpose of the safety valve
to protect the system from excessive air pressure build up in the event that the governor fails to unload the compressor
what would the pressure protection valve setting be in a normal 120 - 130 psi circuit
150 psi
CMVSS 121 states the low pressure warning device must be activated at a minimum pressure of
60 psi however most systems will come on at 68 - 74 psi
what are the basic components of a primary service circuit
dual-circuit brake valve - relay valve - service brake chambers
how is the secondary brake portion of the treadle valve controlled
by air pressure in the primary portion of the valve
if the primary portion of the treadle valve was to fail how would the secondary be actuated
mechanically by the primary piston
all air brake systems will operate will a certain amount of
lag and drag time
what is the purpose of the relay valve
to speed up application and release time of drive axle service brakes
the relay valve will crack the inlet valve open with how much psi
2.5 - 8 psi
the purpose of the brake chamber is to convert what
compressed air into mechanical energy
what are the basic components that make up a secondary service circuit
dual - circuit brake valve - quick release valve - modulator valves - steer axle service brake chambers
what is the purpose of the quick release valve
is to speed up the exhaust of air from the service chambers
CMVSS 121 states that the parking brake must hold fully loaded air brake equipped vehicles on how much of a grade
20%
what will happen if the vehicle looses both primary and secondary system air pressure
mechanically actuated spring brakes will make an emergency brake application
where would the quick release valve be connected in the system
between the park control valve and the spring brake chambers
where is the anti-compounding double check valve located
installed in the parking / emergency brake circuit
what is the purpose of the spring brake relay valve
to speed up application and release times when spring brakes are being used to back up the primary service circuit
what will the spring brake valve have as integral component
anti - compounding double check valve
what are the two main functions of the spring brake valve
to keep the spring brake chamber released during normal operation
to modulate spring brake application pressure if a loss of pressure occurs
what are the common components of a tractor brake circuit
trailer supply - tractor protection - trailer brake control valve - glad hands - brake light switches
what is the tractor protection valve
it works in conjunction with the trailer supply valve to provide automatic closure of the trailer service lines
what is a ratio valve
it can take the place of the quick release valve and also limits brake application pressure to prevent wheel lockup
what is a bobtail valve
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
what are the functions of the emergency relay valve
. 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
what is dynamiting the trailer brakes
when the relay emergency valve makes a full brake application with full trailer reservoir pressure
what is the purpose of the trailer spring brake control valve
. 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
what is the purpose of a pilot relay and single check valve
transmits a quick undiminished signal to the towing trailer to reduce lag time
what is the purpose of a pressure protection valve
maintains pressure in the inlet port regardless of pressure in the outlet port
can non charging and charging emergency relay valves be interchanged
no
what is the function of the trailer release valve ( synchro valve )
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
