A tractor protection valve (Fig. 38) is usually mounted on the cab or chassis of the tractor. When the trailer-supply valve is open, air passes through the bottom of the tractor protection valve and charges the trailer through the supply line (also called the emergency line).
When should the tractor protection valve pop out?
Between approximately 20-40 PSI on a tractor-trailer combination vehicle, the tractor protection valve and parking brake valve should close (pop out).
When checking the trailer emergency brakes the tractor protection valve should be placed in what position?
Tractor protection valve to close. to inspect the landing gear. The tractor should be positioned: With the tractor frame under the trailer.
At what psi range is the tractor protection valve likely to close?
The tractor protection valve and parking brake valve should close (pop out) on a tractor-trailer combination vehicle and the parking brake valve should close (pop out) on other combination and single vehicle types when the air pressure falls to the manufacturer’s specification (20 – 40 psi).
What happens when a tractor protection valve fails?
When the valve fails to close before pressure drops below 20 psi (138 kPa), the power unit is defective. This vehicle has a violation* that is an OOS condition. 5. When the gladhand couplings are disconnected, the trailer emergency (spring) brakes must also apply automatically.
Which vehicle off track the most?
Off-tracking is defined as the different paths taken by the front and rear wheels in a turn. The longer the vehicle, the greater the difference will be. Thus, the wheels on the front trailer will offtrack more than the tractor’s rear wheels, and the wheels on the rearmost trailer will offtrack most of all.
What is another name for the tractor protection valve?
Any truck designed to pull a trailer with air brakes is going to be equipped with tractor protection system, which consists of the tractor protection valve–just to confuse you [CHCUCKLING] the system and the valve are called the same thing – the tractor protection valve and the red, eight-sided trailer air supply …
What is the main purpose of the tractor protection valve?
Application: Tractor protection valves are commonly mounted at the rear of the cab. The purpose of the Tractor Protection valve is to protect the tractor air brake system in the event of a trailer breakaway or severe air leak. They are also used to shut off air to the trailer before disconnecting the lines.
Which shutoff valves should be open and closed?
All shut-off valves should be open. … When starting a trip, be sure that all shut-off valves are in the open position, except for the last valves on the rear trailer. It is important that air reaches the brakes on all trailers and that the air is not able to escape from the back of the vehicle.
How do you know if your tractor trailer is equipped with antilock brakes?
Remove a tire and look for the ABS sensor on the axle. Trailers and converter dollies built on or after March 1, 1998 are required to have Anti-Lock Braking Systems (ABS). This will be indicated by the presence of a yellow malfunction lamp.
Why should you lock the tractor glad hands to each other when you are not towing a trailer?
Why should you lock the tractor glad hands (or dummy couplers) to each other when you are not towing a trailer? A The connected brake circuit becomes a back up air tank. B If you did not, you could never build system pressure.
What part of the kingpin should the locking jaws?
Check to make sure of the following: There is no space between the upper and lower fifth wheel, the fifth wheel jaws have closed around the shank of the kingpin, the locking lever is in the “lock” position, and the safety latch is in position over the locking lever.
At what PSI do air brakes lock up?
If the pressure in the air system pulls below 60 psi, the parking brake knob will pop out and set the parking brakes. This is a safety feature so the truck will stop, because if the pressure falls too low, the service brakes will not work. The other system component stops the vehicle when you push on the brake pedal.
When spring brakes are on you should never?
Never apply the brake pedal if your spring breaks are activated. Brakes can be damaged if they are subject to both springs and air pressure.
How should you check that your service brakes are working properly?
How should you check that your service brakes are working properly? Wait for normal air pressure, release the parking brake, move the truck forward slowly, and apply the brake pedal firmly. You just studied 70 terms!