Where is the tractor protection control valve located?
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).
What happens when the tractor protection valve closes?
When the tractor protection valve closes, it stops any air from going out of the tractor. It also lets the air out of the trailer emergency line. This causes the trailer emergency brakes to come on, with possible loss of control. (Emergency brakes are covered later.)
What is the tractor protection valve used for?
Tractor protection valves are usually mounted at the rear of the cab. Their job 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 valves are the tractor protection system?
The tractor protection system consists of 2 valves. One is the trailer supply valve (TSV), a push/pull valve located on the instrument panel. The other is the tractor protection valve (TPV), located on the towing vehicle’s frame or body. The TPV is also called a ‘towing vehicle’ protection valve.
When the emergency line loses pressure what happens to the tractor protection valve?
When the emergency line loses pressure, it also causes the tractor protection valve to close (the air supply knob will pop out). Emergency lines are often coded with the color red (red hose, red couplers, or other parts) to keep from getting them mixed up with the blue service line.
How do you test the tractor protection valve PSI?
Explanation You should test the tractor protection valve by allowing the air supply to properly charge, turning off the engine, then releasing air from the system by pressing the brake pedal several times. The tractor protection valve should move into its emergency position when psi drops to an unsafe level.