How do you test the tractor protection valve?

Test the tractor protection valve by listening for air exhausting from the trailer service line with the trailer supply valve closed, the trailer service line disconnected and the service brakes applied. If air is exhausting from the trailer service line, the tractor protection valve is defective.

Tractor Protection Valves. 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.

Also Know, what is the main purpose of the tractor protection valve? The tractor protection valve prevents air loss from the towing vehicle. When air pressure in the trailer supply line drops below 414 kPa (60 psi ), the trailer spring brakes will apply automatically.

Correspondingly, at what pressure must the tractor protection valve operate to pass inspection?

Between approximately 20-40 PSI

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.

How does a pressure protection valve work?

Pressure Protection Valves. 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.

Which shutoff valve is 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 trolly valve?

The trailer hand valve (also referred to as the trolley valve or Johnson bar) is a mechanism that works the trailer brakes. Never use the trailer hand valve while parking because doing so may release the air pressure from the braking system, releasing the brakes that are holding the vehicle in place.

What is a typical valve setting for a pressure protection valve?

This is a normally closed pressure sensing valve which allows air to flow freely in both directions as long as the upstream (primary) reservoir pressure is above the set point of the valve. Typical set points range from 55±5 psi to 85±5 psi.

What is a mv3 valve?

The Bendix® MV-3® dash control module is a two-button, push-pull control valve housed in a single body that accommodates dual circuit supply through a double check valve. The MV-3 valve can duplicate the functions of any existing two- or three- valve push-pull system and has the advantages of reduced plumbing.

What is the purpose of a quick release valve?

Because of the distance that the exhaust air has to travel, there can be a considerable lag time for the brakes to release. This is where the quick release valve comes in. A quick release valve allows the brakes to release quickly and fully, by allowing the pressurized air to exhaust near the brake chambers.

What is brake lag?

The time it takes for an air system to feed air to the brakes and will add an additional 32ft to the total stopping distance is known as brake lag . The air brake lag distance at 55 mph on dry pavement adds about 32 feet. To apply the air brakes during normal stops, push the brake pedal down.

How many times can you take the air brake test?

You can attempt the knowledge test up to three times. If you’re unsuccessful after three attempts, you’ll need to complete an additional 16 hours of air brake theory training before trying again.

At what pressure will the protection valve for your trailer pop out and lock the brakes?

20 to 45 psi

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

Fail Type of vehicle Maximum allowable air loss Straight truck, tractor or bus 21 kPa (3 psi ) per minute Tractor and trailer 28 kPa (4 psi ) per minute Tractor and two or more trailers 41 kPa (6 psi ) per minute

When the low pressure warning is activated you should?

If the low air pressure warning comes on, stop and safely park your vehicle as soon as possible. There might be an air leak in the system. Controlled braking is possible only while enough air remains in the air tanks. The spring brakes will come on when the air pressure drops into the range of 20 to 45 psi.

Why should air tanks be drained?

Why must air tanks be drained? Water and compressor oil can get inside of the tank and can freeze in cold weather and cause brake failure. A parking brake control in the cab allows the driver to let the air out of the brakes.