Question: What Is The Valve Before You Hook Up To Air Lines From Tractor Peterbilt 387?

What is the tractor protection valve?

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.

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.

What color is the tractor air supply valve?

The trailer air supply control on newer vehicles is a red eight-sided knob, which you use to control the tractor protection valve. You push it in to supply the trailer with air, and pull it out to shut the air off and put on the trailer emergency brakes.

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Where is the trailer hand valve located?

Subsequently, one may also ask, where is the trailer hand valve? Often, a hand valve is also fitted on the steering column or the instrument panel of the towing vehicle so the driver can apply the trailer service brakes independent of the towing vehicle’s brakes.

How do you test a tractor protection valve?

To test the tractor protection valve, the trailer supply valve must be closed (pulled out), the trailer service line must be disconnected, and the service brakes applied. No air should be exhausting from the trailer service line. If air exhausts from the service line, the tractor protection valve is defective.

Which shutoff valves should be open and closed?

If you’re only pulling one trailer, the shut off valves should always be closed or else the air will simply escape out the back of the trailer. If you’re pulling more than one trailer, all valves should be open except the very last trailer, which should have all valves in the closed position.

What is a DD3 safety actuator?

DD3 brake chamber This type of chamber is called a DD3 Safety Actuator. Internally, these chambers have a mechanical means of locking a brake in the applied position. A control valve similar to the one used in conventional spring brake systems applies the emergency and parking brakes.

What gear should the tractor engine be in after you have uncoupled?

15. You want to inspect the trailer support. You should place the tractor transmission in which gear after you have uncoupled the trailer? Neutral.

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What will happen if the air lines are crossed when you hook up to an old trailer?

a. What will happen if the air lines are crossed when you hook up to an old trailer? a. The hand valve will apply the tractor brakes instead of the trailer brakes. If the trailer has no spring brakes, you could drive away but you would not have trailer brakes.

What is the emergency air line for?

Emergency air line: The emergency line (also called the supply line ) has two purposes: (1) To supply air to the trailer air tanks, and (2) to control the emergency brakes on combination vehicles. Loss of air pressure in the emergency line causes the trailer emergency brakes to come on.

What is a glad hand converter?

This term refers to the coupling device used to connect the service and supply lines of the trailer to the truck or tractor. These couplers have a snap-lock position and a rubber seal that prevents air from escaping.

When should you use the hand valve?

The trailer hand valve, also called the trolley valve or Johnson bar, is used to work the trailer brakes. It should be used only to test the brakes. Using it while a vehicle is in motion could cause a skid.

What might happen if the trailer is too high?

What might happen if the trailer is too high when you try to couple? If the trailer is too low, the tractor may stike and damage the trailer nose; if the trailer is too high, it may not couple correctly. If there is space something is wrong and the trailer would come loose very easily.

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How can a driver control the trailer brakes independently?

How can a driver control the trailer brakes independently? The purpose of the trailer brake hand valve (30) is to allow the driver to control independently the amount of application air pressure to be directed to the trailer brakes.

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