How does pressure protection valve work?

Relief valves are designed to protect compressed air systems from over-pressurisation by releasing excess pressure. Pressure acts against the valve seat and the force generated opens the valve against a spring tension.

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 controls the tractor protection valve?

Operate the tractor protection valve manually by pulling out the trailer air supply control (red knob). This shuts off the air supply to the trailer and applies the trailer emergency brakes. To resupply the trailer brakes with air, push the red knob in.

When the tractor protection valve is opened it allows air to?

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 color is the tractor protection valve?

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. The TSV has a red colored, eight-sided knob and is controlled by the driver.

When the emergency line loses pressure what happens to the tractor protection valve?


The tractor protection valve will close automatically if air pressure is low (in the range of 20 to 45 psi). 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.

What is a 4 way Protection valve?

The 4-circuit protection valve isolates the individual circuits of the air pressure braking system from each other. … A total failure of the brakes is thus prevented. The 4-circuit protection valve is also responsible for supplying compressed air to the four braking circuits.

What is the purpose of the pressure protection valve in an air over hydraulic brake circuit?

Both the pressure protection valve in the service storage (emergency) line and the relay valve in the service line safeguard the tractor’s air supply, if a loss of air pressure (Fig. 28.72) occurs specifically due to a large air leak in the flexible tractor to trailer coupling hose.

How do slack adjusters work?

How does the slack adjuster work? When the brake is applied, a rod pushes out on the slack adjuster, which then turns the S-cam to force the brake shoes apart to apply the friction necessary to slow the truck.

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At what measurement is the safety valve usually set to open?

At what measurement is the safety valve usually set to open? 150 psi. You should drive more quickly so that you will be able to keep the trailer and tractor straight.

What does the blue service line do?

The blue line is the service brake air line. when the foot valve is applied to apply the tractor brakes, this applies the trailer brakes. There is also a third line, the electrical cord that supplies electric power for lights, signals and ABS brakes.

Why do brakes fade?

The friction caused by the brake pads pressing against the rotors stops the car. … Brake fade occurs when the heat doesn’t have time to dissipate, like when you keep your foot on the brake pedal in stop-and-go traffic, drive aggressively, brake down a long hill, or drive with an overloaded vehicle.