D - Trailer Air Brake System Components

Question 1

The most significant difference between a pre-CMVSS 121 trailer and a CMVSS 121 trailer is that:

Answer 1

Pre-CMVSS 121 trailers are equipped with air-supplied parking and emergency brakes.

Question 2

The function of the trailer service line is to:

Answer 2

Carry service air pressure from the tractor tot he trailer.

Question 3

One of the functions of the trailer supply line is to:

Answer 3

Carry supply air to charge the trailer reservoir(s).

Question 4

The one-way check valve in the relay emergency valve on a pre-CMVSS 121 trailer prevents:

Answer 4

Trailer service reservoir pressure fro falling if air pressure falls in the trailer supply line.

Question 5

One way of releasing the brakes after an emergency brake application on a pre-CMVSS 121 trailer is to:

Answer 5

Drain the trailer air reservoir.

Question 6

One safety precaution you must observe when parking a pre-CMVSS 121 trailer is:

Answer 6

Trailer wheels must be blocked.

Question 7

Loss of air pressure in trailer supply line on a CMVSS 121 trailer results in:

Answer 7

Applying the trailer spring brakes.

Question 8

When charging a CMVSS 121 trailer equipped with an SR-5 trailer spring brake control valve, the trailer:

Answer 8

Spring brakes release before the trailer air reservoirs are charged.

Question 9

In order for a towing trailer to be towed as a single unit, the:

Answer 9

Shut-off valves in the service and supply lines must be closed.

Question 10

The component on a towing trailer that vents the supply line to the towed trailer is:

Answer 10

Quick release valve.

Question 11

The term cracking pressure refers to the:

Answer 11

Pressure required to overcome internal friction in an air brake valve.

Question 12

The advantage of a pilot relay valve over a standard relay valve is that it:

Answer 12

Has no difference between incoming signal pressure and delivery pressure.

Question 13

The delivery pressure from the pilot relay valve on a towing trailer is sent to the:

Answer 13

Service line to the towed trailer and the service relay valve.

Question 14

The purpose if the spring acting on the upper surface of the pilot relay valve is to:

Answer 14

Reduce the time required to apply the trailer brakes.

Question 15

The function of the pressure protection valve installed in the supply line to the converter dolly air reservoir is to:

Answer 15

Ensure that dolly parking/emergency brakes release before the dolly reservoir is charged.

Question 16

The one-way check valve in the pressure protection valve on a converter dolly prevents:

Answer 16

Reservoir air pressure from falling if dolly supply line pressure is lost.

Question 17

The trailer release valve is installed on a converter dolly to:

Answer 17

Ensure that air pressure is allowed to build up in the towing trailer and converter dolly before it flows to the following trailer, prevents tractor supply circuit pressure from falling too low when trailers and dollies are charged, keeps the operator from manually holding the trailer supply valve in for a long period while the trailers and dollies are charged.

Question 18

The pilot relay valve on the converter dolly relays:

Answer 18

Service air pressure to the relay emergency valve on the dolly and the service line to the following trailer.