Where is the hand valve on a tractor trailer?
The 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 valve while driving?
What is a brake hand valve on a trailer?
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. .Advertisements. CONTINUE READING BELOW What is a brake hand valve?
What is the purpose of the 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.
What does the protection valve do on a trailer?
The protection valve will either activate or deactivate the air supply to the emergency line which keeps the trailer brakes on (activated) or off (deactivated). And if the protection valve does that, then what the heck does the trailer handle valve do?
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.
What is a trailer brake 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. Do not use it in driving because of the danger of making the trailer skid.
What is a hand valve on a 18 wheeler?
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).
What color valve is the trailer parking brake?
redThe two push-pull valves -- the yellow one for tractor brakes and the red one for trailer brakes – are awkward to release because they must be pushed hard and held before brakes are released.
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 name of the valve that supplies the trailer with air?
A relay valve is an air-operated valve typically used in air brake systems to remotely control the brakes at the rear of a heavy truck or semi-trailer in a tractor-trailer combination.
What is the red air line on a tractor trailer?
emergency brakeThe red line is the air line for the trailer's emergency brake. The green line is the electrical line. The blue line is the air line for the trailer's service brake. Connect these lines to the corresponding couplers and socket on the trailer before moving the trailer.
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.
What is the trailer brake used for on a semi?
Semi-truck trailers have two brakes on each axle. These are air brakes that use compressed air to pressure the brakes and slow down the wheels. With an average weight of 40,000 lbs, trailers need to have brakes to help the truck slow down as efficiently as possible, especially when going downhill.
What does it mean if the red valve is pulled out?
In the event of a loss of tractor air pressure, the red valve on the dash pops out, closing off the air supply from the tractor to the trailer. This will simultaneously engage the trailer spring brakes and usually cause full wheel lock-up on the trailer.
What is the main purpose of a trailer shut off valve?
Shut-off valves (also called cut-out cocks) are used in the service and supply air lines at the back of trailers used to tow other trailers. These valves permit closing the air lines off when another trailer is not being towed.
What is the yellow air brake knob?
parking brake control valveThe parking brake control valve — the one with the yellow button — has no Federal Motor Carrier Safety Administration (FMCSA) regulations specifying the pressure at which it must automatically trip to apply the vehicle parking brakes.
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.
When normal driving some drivers use the hand valve?
In normal driving, some drivers use the hand valve before applying the brake pedal to prevent a jackknife.
How does a spring brake valve work?
A spring brake control valve is normally a push/pull type valve fitted with a yellow, four-sided knob located near the driver (See diagram 4-3). Most spring brake control valves are pushed to supply air and release the spring brakes, then pulled to exhaust air and apply the spring brakes.
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.