Often asked: What Is A Tractor Protection Valve On A Semi?

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.

What color is the tractor protection valve?

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. The driver opens (pushes in) the TSV when a trailer is being towed and closes it (pulls out) when there is no trailer present.

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.

Where are the shut off valves on a tractor trailer?

Shut – off Valves These valves permit closing the air lines off when another trailer is not being towed. You must check that all shut – off valves are in the open position except the ones at the back of the last trailer, which must be closed.

What is a Johnson bar on a semi?

A Johnson bar is a hand lever with several distinct positions and a positive latch to hold the lever in the selected position. Truck drivers call the lever control for air-operated trailer brakes ” Johnson bars “. On Caterpillar tractors, the forward/reverse lever is also called a Johnson bar.

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

What is the blue air brake button for?

The yellow one controls brakes on all axles, the red is only for trailer, and the blue is only for the truck unit.

What is the maximum air loss rate for a tractor and trailer?

Air loss rate should be less than 3 psi in 1 minute for a single vehicle. Air loss rate should be less than 4 psi in 1 minute for combination vehicles (vehicles with a trailer ).

What color is the supply line on a tractor trailer?

Generally these lines are color coded where the service line is blue and the supply line is red. If the trailer connectors are not color coded, then both are usually black or silver and the emergency line will connect to the receptacle closest to the driver’s side on the front of the trailer.

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.

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 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.

When should you drain your air tanks?

Each air tank is equipped with a drain valve in the bottom. There are two types of drain valves: Manually operated by turning a quarter turn (see Figure 5-1) or by pulling a cable. You must drain the tanks yourself at the end of each day of driving.