Skip to Content

What is a Hand Valve on a Truck?

What is a Hand Valve on a Truck?

The hand valve is the major component of the braking system present in most semi trucks to control the brakes of the trailers for the safety of passengers, drivers, and other people.

What is a Hand Valve on a Truck? The hand valve is present on the truck’s steering column to control the brakes of the trailers. It is used to inspect the functioning of the trailer’s brake. In addition, people also use it as an emergency brake for downhill movement to control wheels from skidding on snowy roads. You should avoid using it during driving because it can cause skidding. Do not use them for parking because the sudden leak of air pressure causes a problem. 

You should check your truck’s trolley valve before going anywhere to apply brakes for towing objects safely.

What is a hand valve on a semi truck?

It is the extension of the braking system that is present in most semi-trucks. In addition, these vehicles have trailers behind them, making it difficult to control them while driving.

Due to their heavy weight, slipping and unbalancing issue comes in these vehicles. These are designed to carry heavy weight, so it is necessary to control their movement with the movement of semis.

It provides the extra safety feature during movement and helps smooth movement. Moreover, it is also known as a trolley and Johnson valve.

The primary purpose of this braking system is to control the trailer’s brakes irrespective of the tractor’s movement.

Automobiles with connected trailers have additional valves to control the braking system of these towing components to decrease the chances of accidents.

How does a hand valve work on a truck?

The hand valves in the trailers work through the air pressure system to supply air pressure. So you have to push it in means closing them.

Control the air pressure supplied to the service lines by pushing or closing the valve.

The suppression of air pressure supply releases the braking system, which applies brakes of the connected Trailor.

The trailer receives high pressure when you use the valve or hand brakes simultaneously. This is because the movement of air creates pressure through the service lines.

The system only works when the pressure between lines is almost 25 to 40 psi. The older model of the semi trucks is operated by the hand lever rather than a knob.

The latest models are equipped with a knob that is easy and quick to use. You can shift this knob to the normal position for pulling the trailers, and the emergency position is used to put them in emergency brakes.

Where is the hand valve located on a truck?

The drivers must know about the location of this part for its appropriate usage. In addition, you should know about it to apply it in an emergency.

The steering column is present on the power steering wheel that is on the very front side of the driver.

This steering column contains several buttons and components that perform their specific function and assist in safe and comfortable driving.

The location at the driver’s side is essential so it can apply the trailer brakes irrespective of the movement of the tractor.

All air basics parts are on these steering columns, including the hand valve. The location of these components on the front side of the driver is necessary for their easy access in an emergency.

It has an octagonal shape and comes with a knob-like structure or a lever operated by hand. Its shape varies from model to model because of the addition of the latest features.

In old models, the lever is present with this octagonal structure, and you must operate it by hand. The new models have great advancement and a knob on the upper side of the octagonal design.

You can shift or press this knob in various directions for its appropriate functioning.

What is the purpose of a hand valve on a truck?

The installation of this device is essential in semi trucks because of the tractors attached to their backside.

Check brakes of trailers

The brakes are also present on the trailers for their appropriate movement. You can only check these brakes by using this component.

Inspecting brakes before going anywhere is essential for the safety of drivers, vehicles, and the luggage in these trailers.

You can inspect them by opening the service lines at the rear end of the tractor. Then, move to the rear end and check the air pressure in the service lines.

First of all, you have to apply the hand brake of the trailers and then move towards the rear side of the rig of towing vehicle.

The emergency line shut-off valve is present at the end of the rear side. You should open this valve and hear the sound of air escaping.

The brakes of the trailers are working efficiently and are fully charged if you hear the air noise from these valves.

Another method is used to check the working of this air brake system. You should check the air pressure in the lines and release the brake pedal.

Move the semi-truck slowly and apply the brakes with trolley valves. You can see that air pressure moves through service lines to stop the wheels.

Control trailers in hilly areas

Movement in hilly areas with these heavy and fully loaded areas is challenging. The drivers have to show their full concentration in controlling the tractor and trailers.

The minor distraction disturbs the control and causes a severe accident. In addition, the downward and upward movements are difficult.

The downhill movement requires more safety and control, while the uphill movement requires more power to move these heavy vehicles on sloppy roads.

The trolley valves on the steering column and the driver’s side are beneficial for downhill movement.

You have to control the movement of the trailers because they can roll over due to inappropriate application of brakes.

You should keep their tires bound and control their movement while applying brake pressure through these valves.

Better grip on Snowy roads

Most of the time, you have to deliver the freights during cold weather. The snow on the road during the winter season can decrease the traction of tires.

You can feel slippery driving in the presence of the snow. The semi-truck drivers also said it is challenging to move on slippery or snowy roads.

Moreover, it is also difficult to control the movement of heavy trailers. Therefore, you should engage hand valves to manage their movement on these slippery roads.

It is helpful to apply the brakes of the trailers for their appropriate stoppage and decrease the chances of out-of-control movement that can cause serious accidents.

Prevent skidding of trailers

The skidding of heavy trailers in the semi-truck is a common issue because of their large size and weight.

The wheels sometimes cannot maintain their grip on the road and become slippery. As a result, people use the hand brakes of the associated truck to keep them at their position during driving.

Keeping the wheels in the same direction and maintaining their better grip on the road is beneficial for smooth and comfortable driving.

Emergency brakes

Many people apply these brakes in an emergency to stop the heavy-weight trailers. Sometimes the braking system of this towing object is not working correctly.

You should use the trolley valve in an emergency to stop them. The uncontrolled movement on the highways can cause collisions with other cars and trucks.

It works as a safety system to tackle emergencies on the road. It can decrease the repairing cost by reducing the chances of accidents.

Why should you not use the trailer hand valve for braking purposes?

Many people said using trolley valves to apply brakes on the trailers is harmful. It can increase the chances of rolling over because of the sudden application of brakes.

You should avoid using them for braking purposes because of their harmful effect. In addition, when you use them during driving, it can cause skidding issues which is a dangerous situation.

Moreover, when you use the trolley valve for braking purposes, it can cause leakage of air through the system.

The air is used to unlock the brakes and can leak out from the lines and cause a decrease in air pressure.

Therefore, you should only use it to inspect the brakes f the trailers for safe and comfortable driving.

Drivers should also avoid their applications during driving to stop the trailers.

Can you use a Hand valve for the parking of trailers?

Most people use this component for emergency brakes and parking purposes. For example, the parking brakes are present in the trucks when you want to park your automobiles.

Parking while engaging the trolley valve is dangerous because a sudden leak of air pressure causes the forward movement and skidding of tires.

You can use chocks or heavy stones to stop the tires from skidding if you do not want to engage the parking brakes.

You should avoid them for parking because of their harmful effects and air leakage through the system.

What is the difference between a hand valve and a foot valve?

The foot valve is also present in the semi-trucks, and it is helpful to control the movement of the trailers and tractors when you press them fully.

The hand valve only controls the brakes of the trailers, but it performs a dual function. In addition, the chances of skidding are also less when you apply them during driving.

It is present with the brake pedals and on the floor or firewall of the cab. The maximum air moves through the service lines when you press it.

In addition, the maximum air is sent to all vehicles’ brakes for appropriate functioning.

Do all trucks have a hand valve? 

All of the semi trucks have towing vehicles behind them, and it is difficult to control their movement during driving.

The hand or trolley valves are necessary for these types of automobiles for safe driving. It is present in all trucks with towing trailers behind them.

It is essential for the ones that do not have a spring barking system. The air pressure system from the trolley valves helps to stop the wheels and keep them in their place.

Related Articles:

Do trucks have bigger steering wheels than cars?

Why Are Toyota Tacoma Seats So Uncomfortable?