Self Test D Flashcards
The most significant difference betweent a pre-CMVSS 121 trailer and CMVSS 121 trailer is that?
a) pre cmvss 121 trailers are equipped with spring applied parking and emergency brakes
b)Pre cmvss 121 trailers are equipped with air-applied parking and emergency brakes.
c) Pre cmvss 121 trailers are not equipped with parking/Emergency brakes.
d) cmvss 121 trailers are equipped with air applied parking and emergency brakes.
b)Pre cmvss 121 trailers are equipped with air-applied parking and emergency brakes.
The functin of the trailer service line is to:
a)carry service air pressure from the tractor to the trailer.
b) charge the trailer reservoirs
c) trigger trailer parking/emergency brake application
d) transmit air from the trailer supply valve
a)carry service air pressure from the tractor to the trailer.
one of the functions of the trailer supply line is to?
a) trigger the application and release of trailer service brakes
b) carry service air pressure from the tractor to the trailer
c) carry supply air to charge trailer reservoirs
d) transmit air from the dual circuit brake valve to the trailer
c) carry supply air to charge trailer reservoirs
the one way check valve in the relay emergency valve on a pre cmvss 121 trailer prevents?
a) supply line pressure falling if air pressure falls in the trailer reservoir
b) service line pressure from falling if air pressure falls in the trailer reservoir
c) trailer service reservoir pressure from falling if air pressure falls in the trailer supply line
d) trailer spring brakes from applying if air pressure falls in the trailer supply line
c) trailer service reservoir pressure from falling if air pressure falls in the trailer supply line
one way of releasing the brakes after an emergency brake application on a pre cmvss 121 trailer is to?
a) drain the trailer reservoir.
b) charge the trailer air reservoir
c) mechanically cage the spring brakes
d)restore pressure in the trailer service line
a) drain the trailer reservoir
**air in trailer supply line is restored to 60psi
one safety precaution you must observe when parking a pre CMVSS 121 trailer is?
a) trailer reservoir must be drained
b) trailer wheels must be blocked
c) the spring brakes must be applied
d) the spring brakes must be caged
b) trailer wheels must be blocked
Loss of air pressure in trailer supply line on a CMVSS 121 trailer results in
a) applying trailer service brakes
b) losing tailer reservoir air pressure
c) dynamiting the trailer service brakes
d) applying the trailer spring brakes
d) applying the trailer spring brakes
When charging a CMVSS 121 trailer equipped with Sr-5 trailer spring brake control valve, the trailer
a) reservoirs are charged at the same time as the trailer spring brakes are applied
b) reservoirs are charged at the same time as the trailer spring brakes are released
c)Spring brakes release before the trailer air reservoirs are charged
d) reservoirs are charged at the same time as the trailer service brakes are released
c)Spring brakes release before the trailer air resevoirs are charged
In order for a towing trailer to be towed as a single unit, the?
a) spring brakes must be mechanically caged
b) shut-off valves in the service and supply lines must be closed
c) shut-off valves in the service supply lines must be opened
d) trailer supply valve must be pulled out
b) shut-off valves in the service and supply lines must be closed
the component on a towing trailer the vents the supply line to the towed trailer is?
A) quick release valve
b) the shut-off valve
c) the trailer spring brake valve
d) the pilot relay valve
A) quick release valve
the term cracking pressure refers to?
a) pressure applied to an air brake valve
b) pressure delivered from an air brake valve
c) pressure required to overcome internal friction in an air brake
d) maximum pressure that an air brake valve can withstand
c) pressure required to overcome internal friction in an air brake
the advantage of a pilot relay valve over a stand relay valve is that?
a) has no difference between incoming signal pressure and delivery pressure
b) requires less air pressure to operate
c) reduces delivery air pressure
d) increases delivery air pressure
a) has no difference between incoming signal pressure and delivery pressure
the delivery pressure from the pilot relay valve on a towing trailer sent, is to?
a) reduce the time required to release the traile rbrakes
b) increase application pressure to trailer brakes
c) reduce the time required to apply the trailer brakes
d) hold the inlet valve open when the brakes are released
c) reduce the time required to apply the trailer brakes
the function of the pressure protection valve installed in the supply line to the converter dolly?
a) allow supply air to charge the dolly reservoir before the dolly parking brakes are released
b) allow supply air to charge the dolly reservoir before the dolly spring brakes are released
c) ensure that dolly parking/emergency brakes release before the dolly reservoir is charged
d) limit dolly reservoir pressure 70 psi
c) ensure that dolly parking/emergency brakes release before the dolly reservoir is charged
the one-way check valve in the pressure protection valve on a converter dolly prevents?
a) reservoir air pressure from falling if the dolly supply line pressure is lost
b) supply line pressure from falling if the dolly reservoir pressure is lost
c)spring brake compounding
d) parking/ emergency brakes from being released before the dolly reservoir is charged
a) reservoir air pressure from falling if the dolly supply line pressure is lost
