What is the purpose of the trailer hand valve?
The trailer hand valve is used to apply the trailer service brakes independent of the towing vehicle's brakes. The trailer supply valve is usually a push/pull type valve near the driver that supplies air to the trailer's brake system through the supply line.
How does a hand valve work?
Closing the hand valve releases the brakes by closing off application air. Air pressure in the chambers and lines will exhaust, also as explained in the previous foot-valve application. Click for larger image. CAUTION: Trailer brakes must not be used to hold a parked vehicle that is left unattended.
What is the hand valve?
The hand valve, or "spike" (Fig. 39) is added so that you can apply the trailer's brakes independent of the tractor. The hand valve is typically supplied from primary and secondary circuits and plumbed to a double-check valve (which is also fed from the foot valve).
Where is the trailer hand valve located?
steering columnThe hand valve, as shown in Figure 2-7, is normally located on the steering column and its function is to apply the trailer brakes only, while the foot valve operates both the tractor and trailer brakes.
Why should you not use the trailer hand brake valve while driving?
6.2.1 – Trailer Hand Valve Do not use it in driving because of the danger of making the trailer skid. The foot brake sends air to all of the brakes on the vehicle (including the trailer(s)). There is much less danger of causing a skid or jackknife when using just the foot brake.
How do you control the trailer brakes independently?
The parking brake controls the spring brakes on the tractor. When you pull the knob out, it causes the trailer supply valve to pop out, applying both the tractor and trailer parking brakes. You can independently release the trailer brakes by pushing only the trailer air supply valve in.
How do you use hand brakes on a trailer?
0:231:42How to use a Braked Trailer | Hirepool NZ - YouTubeYouTubeStart of suggested clipEnd of suggested clipSimply flick down the reverse latch to stop the trailer from engaging the brakes. It's important toMoreSimply flick down the reverse latch to stop the trailer from engaging the brakes. It's important to remember that because the brakes won't engage while reversing.
How does a trailer control valve work?
The trailer control valve in the towing vehicle causes the brake system of a trailer to be supplied with compressed air. It also controls the trailer brake system via the service brake system of the towing vehicle and via the parking and auxiliary brake valve.
What are the 4 types of valves?
The four valves in order of circulation are:Tricuspid Valve. Has three leaflets or cusps. ... Pulmonary Valve (or Pulmonic Valve) (link opens in new window) ... Mitral Valve. Has two leaflets. ... Aortic Valve. Has three leaflets, unless it's abnormal from birth, i.e., bicuspid aortic valve.
What is another name for the trailer hand valve?
The trailer hand valve (also called the trolley valve or Johnson bar) works the trailer brakes. The trailer hand valve should be used only to test the trailer brakes.
How do you test a trailer hand valve?
0:516:54How to Test Tractor Protection System for CDL Air Brake InspectionYouTubeStart of suggested clipEnd of suggested clipThe first one is to pump down the air pressure in the system between 20 and 45. The trailer airMoreThe first one is to pump down the air pressure in the system between 20 and 45. The trailer air supply will pop out shutting air off to the trailer.
What color is the trailer hand valve?
redThe trailer air supply control on newer vehicles is a red 8-sided knob used to control the tractor protection valve. 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.
When should you use hand valves?
6.2. The trailer hand valve should be used only to test the trailer brakes. Do not use it in driving because of the danger of making the trailer skid. The foot brake sends air to all of the brakes on the vehicle (including the trailer[s]).
How do manual solenoid valves work?
One way is to simply turn the solenoid (the black cylinder with 2 wires) counter-clockwise a 1/4 to 1/2 turn. To shut off the valve, twist the solenoid clockwise until it is snug on the valve. The other way is to use the bleed screw the same way, loosen the screw enough to realease air (1/4 to 1/2 turn).
What are the 4 types of valves?
The four valves in order of circulation are:Tricuspid Valve. Has three leaflets or cusps. ... Pulmonary Valve (or Pulmonic Valve) (link opens in new window) ... Mitral Valve. Has two leaflets. ... Aortic Valve. Has three leaflets, unless it's abnormal from birth, i.e., bicuspid aortic valve.
How do you manually operate a control valve?
0:091:57How Does a Manual Handwheel Work on a Control Valve? - YouTubeYouTubeStart of suggested clipEnd of suggested clipPosition for automated control the side mounted hand wheel pushes against the force of the actuatorMorePosition for automated control the side mounted hand wheel pushes against the force of the actuator spring to move the valve in one direction. And the actuator spring moves the valve in the other.
Why do you need a hand valve on a trailer?
When the hand valve and brake pedal are used at the same time, the trailer will receive the higher pressure.
What is trailer brake?
Vehicles that are designed to tow trailers must be fitted with additional valves used only for the trailer. The brake system of a converter dolly that attaches one trailer to another is essentially the same as a trailer system.
How does a tractor protection valve work?
Once the trailer supply valve closes , the tractor protection valve on the towing vehicle also closes. This prevents air loss out of the towing vehicle when there is no trailer attached . The trailer supply valve controls the tractor protection valve. When the trailer supply valve is opened to allow air to the trailer, air pressure is also directed to open the tractor protection valve and allow air to the trailer service line. When the trailer supply valve is closed, air pressure exhausts from the tractor protection valve and it closes by spring force. When the tractor protection valve is closed, air enters the valve but does not pass through it.
What is spring brake priority?
This means that, in a system with “spring brake priority,” the air from the towing vehicle first fills the air tank for the spring brakes to a certain pressure before filling the air tank for the service brakes. Most manufacturers have changed the trailer spring brake valves on spring brake priority systems such that, if there is air loss to the service brakes, the spring brakes will lose sufficient air that they will begin to apply.
What pressure do trailer brakes apply?
The spring brakes must apply automatically when the air pressure in the trailer supply line drops below 414 kPa (60 psi ).
What is the connection between a trailer and a brake system?
One connection carries air to fill the trailer’s tanks and is called the supply or emergency line . The other carries pressure for the service brakes and is called the service line.
What is a trailer brake subsystem?
The trailer brake subsystem includes components and features on both the trailer and the truck or tractor that tows it. This chapter explains the major components of the trailer brake subsystem and how they work.
infoclown Bobtail Member
Any instructor will confirm that using the trailer hand brake to stop the vehicle is not appropiate.Yet there are still truckers out there who continue to use it improperly.I can tell by the burning rubber when I'm following them.Some are owner operators who think they're saving their own tractor brakes.Trucking company owners don't seem to care that their trailer brakes and tires will wear down prematurely.Do any of the other idiots realise that when they apply the brake pedal that all brakes are applied?In the past truckers were slow about trusting the experts on front brakes & anti-lock brakes.I was driving these trucks before these safety features were forced on us.Now I wouldn't dream of driving without them..
dave26027 Road Train Member
It's a dangerous habit to pull the handbrake down in an emergency. Through the years I've almost been hit a few times by the trailer next to me as it slid sideways with the tires locked up. The last time it was a postal service trailer in Dallas- he suddenly realized traffic 1/4 mile ahead of him was stopped.
brsims Road Train Member
Having never been in a jackknife situation (knock on wood and pray!), I've only ever used the trailer brake lever to check the trailer brakes as part of my Pretrip. I thought that was what it was there for!
Tazz Road Train Member
That was probably the last time I can remember using it, and It worked. Luck?
Tazz Road Train Member
Personally I don't think they should be looking at any control until they both know what it is, it's proper functions, and the dangers of misuse.
PackRatTDI Licensed to Ill
My tractor doesn't even have one. Its an ex Covenant tractor. Are some fleets simply not ordering them on their equipment?
PackRatTDI Licensed to Ill
Fwiw, I only used it to keep the truck from moving on a Cat scale when I drove for Stevens. Even then I couldn't do that with the T2000, only the T600's, the T2's valve wouldn't stay appied.
