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.

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.)

How does tractor protection valve work?

When the pressure in the supply line reaches 45 psi, the service line port of the tractor protection valve opens. … This allows application air pressure to travel down the service line to the trailer when a brake application is made.

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What does a pressure protection valve do?

Protects the air brake system in the event of a leak or failure within the air suspension system.

What will occur if the supply emergency line ruptures?

Rupture of the supply line (or an uncoupling of the supply line glad hands – Fig. 47) results in a pressure drop in the supply line between the trailer-supply valve and relay emergency valve. This triggers the emergency action of the relay emergency valve, placing the trailer brakes into emergency application.

What position should the tractor protection valve be?

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.

At what pressure must the tractor protection valve operate to pass inspection?

Title 49, Section 393.43, which addresses breakaway and emergency braking, establishes an “explicit requirement that the tractor protection valve or similar device operate when the air pressure –both primary and secondary reservoirs – on the towing vehicle is between [20 and 45 psi].” The regulation is intended to …

How do you test a tractor protection valve?

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.

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What is tractor protection system?

The trailer-supply valve and tractor protection valve make up the tractor protection system. … This system prevents air loss from the tractor when not hooked to a trailer or if a trailer breaks away.

What is a emergency relay valve?

Relay Emergency Valve (REV)

The relay emergency valve controls the air brake system of a trailer and provides the “emergency brake function”. … Versions with a predominance device can adapt the braking effect between towing and towed vehicle.

What is the air protection valve?

Pressure protection valves are used to isolate auxiliary air systems from the brake system. This is done to preserve air for braking in the event that the auxiliary system develops a major leak.

What is a 4 way Protection valve?

The four-circuit protection valve (English Four way protection valve or Multi-Circuit Protection Valve ) is a component of the multi-circuit air brake system for motor vehicles . It is part of the pressure procurement system and has the task of protecting the individual compressed air circuits from one another.

What happens if a line on the primary circuit ruptures?

If the service line is ruptured or disconnected, no action will take place until a brake application is made. … Rupture of the service line will result in the escape of air pressure, if the brake application is held long enough to cause enough loss of pressure in the tractor system.

What happens to the trailer emergency brakes if there is a loss of pressure in the emergency line?

A major leak in the emergency line will cause the tractor protection valve to close and the trailer emergency brakes to come on. But the brakes will hold only as long as there is air pressure in the trailer air tank. Eventually, the air will leak away and then there will be no brakes.

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What will happen if the trailer supply line is disconnected from the truck?

Trailer couplers or “gladhands”

When trailer lines are crossconnected, the trailer brakes will not work correctly – the spring brakes may not release, the towing vehicle may lose air and the service brakes will not function properly.