COUPLING AND UNCOUPLING
To operate a tractor-trailer safely, proper coupling and uncoupling techniques are essential. Any driver who is unfamiliar with the correct coupling and uncoupling techniques is asking for disaster. Improper connection may lead to cab and freight damage, litigation, penalties, fallen trailers, damaged air, and electrical lines, and other significant repercussions. These effects may always be avoided. To ensure that the operation is always carried out in the same precise order, every time, experienced drivers are expected to be knowledgeable about safe coupling and uncoupling procedures. Before trying a coupling or uncoupling technique, be familiar with the protocols and the risks.
The following coupling process can assist safeguard you, your vehicle, your cargo, and other people from harm and damage. Never try to pair a rig without going through this process.
Step 1: Inspect the ﬁfth wheel and kingpin —Before trying to couple the tractor to the trailer, the fifth wheel on the tractor and the kingpin on the trailer must both be examined to assist guarantee a secure connection. When examining the 5th wheel:
Check for damaged, loose, or missing parts.
Verify that the fifth wheel is securely attached to the tractor. Verify that the frame and all weld locations are free from fractures and that the bolts that are connected are securely fastened.
If required, grease the fifth wheel plate. A poorly oiled fifth wheel can create steering issues due to increased friction between the tractor and trailer, which will be particularly visible in curves.
Verify that the fifth wheel is positioned correctly for connection. With the jaws open and the release handle in the unlocked or released position, it should be tipped down toward the tractor's rear.
To prevent the fifth wheel from moving if you have a sliding fifth wheel, make sure that it is secured and that all of the pins are properly placed.
Verify that the fifth wheel's placement prevents the tractor from colliding with the landing gear.
Verify that the trailer kingpin is not damaged, twisted, or loose.
Step 2: Check area and secure trailer — It is necessary to perform the coupling process in an area with appropriate room for safe movement. Additionally, before backing up to the trailer, it should be secured against movement in case your tractor makes touch with it.
Make sure the area around the vehicle is clear.
Check the cargo, if any, to make sure it will not shift when the tractor and trailer are coupled.
Chock the trailer wheels, or if the trailer has spring brakes, make sure they are applied.
Step 3: Position the vehicle — Embark on the tractor. Instead of at an angle, place the tractor straight in front of the trailer. The fifth wheel's throat should be lined up with the kingpin as well.
Backing beneath the trailer at an angle might cause it to tilt and damage or shatter the landing gear, which could lead to the trailer falling or colliding with anything. If you must back at an angle, periodically exit the cab to verify the fifth wheel's alignment with the kingpin.
Use your outside mirrors to position the tractor while keeping an eye on the drive axle tires and the sidewalls of the trailer. To gain an accurate view of the alignment of the units, you must frequently check both the left and right mirrors
The outer edge of the driving axle tires and the trailer edge should create a straight line if the trailer is 8 feet (96 inches) wide. Adjust your position so that the tractor tires are a few inches inside the outer edge of the trailer if it is broader (many trailers are now 8-12 feet (102 inches) wide).
Step 4: Back slowly into position — Start slowly pulling the tractor up to the front of the trailer. Stop right before the trailer's fifth wheel contacts it. Avoid bouncing the trailer or raising it onto the fifth wheel. You should be able to compare the fifth wheel height to the trailer height at this stage. Airlines should not be connected yet.
Step 5: Secure the tractor — Shift the transmission into neutral and engage the parking break before exiting the cab.
Step 6: Check the trailer height — Check the trailer's height concerning the fifth wheel now. When the tractor is backed beneath the trailer, the tractor will elevate it slightly so that it makes contact with the center of the fifth wheel.
If the trailer is excessively low, the tractor might hit it and damage the trailer's nose. The back of the cab might be hit if the trailer is too high, preventing it from coupling properly or entirely missing the pin.
If the tractor is equipped with adjustable air suspension, you may raise or lower the fifth wheel as well as the trailer as required by twisting the landing gear up or down. Once the necessary height has been attained, lock the landing gear crank.
Finally, if the tractor has been moved at all, ensure sure the fifth wheel and kingpin are in alignment and that the jaws are open.
Never walk underneath a trailer that isn't being held up by a tractor.
Step 7: Connect the airlines — Check your trailer brakes before attaching the tractor to it. The brakes on the majority of trailers are already set, however, if your trailer is really old (built before 1973), you may need to provide air to set the brakes. For the brakes to function effectively, the connection must be made appropriately. Even if the trailer has spring brakes, it's a good idea to connect the airlines at this point.
There are two air lines to be connected: the "emergency" line as well as the "service" line. The lines may be identified from one another in several ways:
They may be stamped with the words “Service” and “Emergency.”
They may be color coded, with blue or black for the service line and red for the Emergency line.
The glad hands may be coded by shape, with square glad hands for the service line and round glad hands for the emergency line.
Check all four glad hand seals (rubber grommets) for cracks or other damage, and then connect the tractor’s emergency air line to the trailer’s emergency glad hand (usually on
the right side when facing the trailer). Make sure the connection is ﬁrm, and then engage the safety latch or other mechanism to keep the lines together. Connect the service line in the same manner.
To prevent the glad hands from uncoupling, make sure airlines are securely secured so they won't be crushed or trapped while the tractor is backing beneath the trailer.
Step 8: Fill the trailer with air – This step should only be carried out if you are certain that the brakes are not already set (on a trailer built before 1973) or if you are unsure of their status. Push in the red air supply knob from the cab while the engine is off to provide air to the trailer braking system.
Hold off until the air pressure returns to normal. Listen for escaping air and look for considerable air loss in the air brake system pressure gauge (a sign that a problem exists).
Apply and release the trailer brakes while keeping an ear out for their sound. When the brakes are applied, you should hear them engage, and when they are released, you should hear air escaping.
Step 9: Start the engine and set the trailer brakes — Once you're certain the brakes are engaged, fire up the engine. Verify that the air pressure is normal.
Pull the red air supply knob or the trailer brake hand control down to engage the trailer brakes (if they haven't been engaged before).
Step 10: Back under the trailer — It's time to make the major connection in Step 10: Go back below the trailer. Release the parking brake on the tractor and shift into the lowest reverse gear.
Slowly drive the tractor below the trailer. When the trailer apron makes contact with the fifth wheel, the trailer should be lifted onto the tractor. When the fifth wheel's jaws tighten around the kingpin, you should stop. A strong hit on the kingpin might seriously harm the kingpin, fifth wheel, landing gear, and/or cargo.
Step 11: Check the connection — To ensure that the trailer is securely fastened to the tractor, shift the tractor into low gear and slowly advance while the trailer brakes are still engaged. When the trailer starts to resist, stop and carry out the test again.
Step 12: Secure the vehicle — Once the connection is strong, engage the tractor parking brakes and put the transmission in neutral. To prevent someone from moving the vehicle while you are below it, turn off the engine and take the key with you.
Step 13: Inspect the coupling — You will check that the coupling is safe and secure in this stage. Bring a flashlight if required since you will have to crawl beneath the trailer to examine the connection.
Check the following:
Check that the top (apron) and lower (platform) fifth wheels are not separated by any space. The fifth wheel plate and trailer apron need to make complete contact. Fix the issue first before moving on (the ground may be uneven, and the kingpin may be on a ridge within the fifth wheel jaws or on top of the closed fifth wheel jaws, which would make it extremely easy for the trailer to come free). If there is a gap, something is wrong.
With a flashlight, get below the trailer and see down the fifth wheel's neck. Verify that the fifth wheel jaws have locked and are around the kingpin's shank, not the head.
Verify that the release arm is secured in place.
Verify that, if there is a safety catch, it is in place over the release arm. (On certain fifth wheels, the catch has to be manually installed.)
If the coupling isn’t right, don’t move the vehicle.
Step 14: Connect the electrical cord and check the air lines — If you haven't already, connect the trailer's electrical cable, then secure the safety catch. If the connection doesn't fit, don't try to push it.
Check for good attachments and any evidence of damage on the electrical cable as well as the airlines. Setting your tractor brakes, releasing the trailer brakes, and listening for any air leakage are effective ways to do this.
Make sure the electrical wire and airlines won't grab the car's moving components or lay on the catwalk.
Step 15: Raise trailer supports and remove chocks — The majority of landing gear cranks feature low and high speeds. Start elevating the landing gear by using the low speed. Change to high speed when the landing gear is weight-free.
Make sure all legs are fully extended while raising the landing gear. Never drive with partially lifted landing gear since it might catch on rail lines or other obstacles.
Lift the landing gear, then securely fasten the crank handle.
When the full weight of the trailer is resting on the tractor, do the following:
Verify that there is enough space between the landing gear and the back of the tractor frame. With a tandem axle tractor and/or a sliding fifth wheel, this is extremely crucial. Insufficient space might cause the tractor to collide with the landing gear while making quick spins.
Verify that there is sufficient space between the trailer's nose and the tops of the tractor tires.
Step 16: Remove chocks — The last step is to take out the wheel chocks and put them away safely. Chocks are typically exclusively used at docks. Make careful to glance at and around your trailer tires since you may not be accustomed to their being there.
The following 12 steps will help you to safely uncouple a tractor-trailer combination.
Step 1: Position the rig — Making sure the parking area's surface is level and strong enough to hold the weight of the trailer is the first step. Surfaces made of sand, gravel, and heated asphalt may all be problematic. Use trailer supports, such as boards, if necessary to keep the trailer from sinking.
Set the tractor and trailer in alignment. Landing gear damage might result from pulling out at an angle.
Step 2: Secure the trailer and ease pressure on locking jaws — To lock the trailer brakes, release the trailer air supply button.
Backing up slowly will reduce strain on the fifth wheel's locking jaws. This will enable you to relieve some of the kingpin-squeezing pressure from the locking jaws.
While the tractor is pressing up against the kingpin, engage the parking brakes. By doing this, the locking jaws of the rig will not be under pressure. Put the engine in neutral and shift the gearbox into Neutral.
Step 3: Chock the trailer wheels — If the trailer doesn't have spring brakes or if you're unsure, chock the wheels. (The trailer's emergency brakes could be released if air leaks out of the air tank there. If the trailer's wheels weren't chocked, it may potentially move.)
Step 4: Lower the landing gear — Look for any damage, excessive corrosion, fractures, broken welds, or other issues with the landing gear. Till the landing gear firmly touches the surface of the ground, lower it.
Check to see that both supports are firmly planted on the ground; if not, move the trailer to a more level area.
Turn the crank in low gear a few more spins to remove some weight off the tractor if the trailer is loaded after the landing gear makes solid contact with the ground. The fifth wheel will be simpler to release and couple the following time as a result. Avoid removing the trailer from the fifth wheel.
Step 5: Disconnect air lines and electrical cord — Disconnect the trailer's airlines. The airline couplers on the rear of the cab may be connected to by the airline glad hands, or they can be coupled together.
To keep moisture out, hang the electrical wire with the socket pointing downward.
To prevent damage to the lines when using the tractor, make sure they are supported.
Step 6: Unlock the ﬁfth wheel — Lift the safety latch or fifth wheel release handle lock (if so equipped). To reach the lock or latch, if required, use a hook or extension handle.
To open the release handle, pull it.
To prevent significant harm if the vehicle moves, keep your legs and feet away from the back tractor wheels.
Step 7: Lower the air suspension — If your tractor has air suspension, deflate the airbags before driving away from the trailer to prevent the tractor's rear from "jumping."
Step 8: Pull the tractor partially clear — Pull the tractor forward while releasing the parking brake until the fifth wheel just touches the trailer's apron plate. If the landing gear should fail or sink, stop while the tractor frame is still below the trailer to avoid the trailer from falling to the ground.
Step 9: Secure the tractor — Put the transmission in neutral, engage the parking brake, and get out of the cab.
Step 10: Inspect the trailer supports — Verify that the ground can support the trailer. Check to see whether the landing gear has any damage. To support the trailer, if required, utilize a trailer safety jack.
Step 11: Pull the tractor clear — Drive the tractor cautiously away from the trailer after releasing the parking brakes and inspecting the area.
Step 12: Raise the air suspension — If your tractor has an air suspension, reinﬂate the air bags (see Step 7 above).
Coupling Twin Trailers
Twin trailer connection requires somewhat more effort than single trailer coupling. When coupling twin trailers, the following procedures should be performed.
Step 1: Secure the rear trailer — Drive the tractor close to the second trailer if it doesn't have spring brakes (pre-1973), then attach the emergency air supply line, fill the trailer air tank, and then disconnect the emergency line. This will activate the emergency brakes on the trailer (if the slack adjusters are correctly adjusted). the wheels, clunk.
Step 2: Couple the tractor and ﬁrst trailer — Couple the tractor and the first trailer by following the steps for coupling tractor-trailers that were previously covered. The heavier-loaded trailer must always follow the tractor in the first place for safe handling on the road. The heavier trailer needs to be at the back.
Step 3: Position the converter dolly — By turning the air tank petcock open, you may release the dolly brakes. Alternatively, use the dolly parking brake control if the dolly has spring brakes.
If the distance is not too significant, maneuver the dolly into place by hand so that it is parallel to the kingpin of the back trailer. Otherwise, pick up the converter dolly using the tractor and first trailer. Place the combination as near to the dolly as you can.
Move the dolly to the rear of the ﬁrst trailer and couple it to the trailer. Lock the pintle hook
Secure the dolly support in the raised position.
Pull the dolly into position as close as possible to the nose of the second trailer.
Lower the dolly support.
Unhook the dolly from the ﬁrst trailer.
Wheel the dolly into position in front of the second trailer in line with the kingpin.
Step 4: Connect the dolly to the front trailer — In front of the dolly tongue, place the first trailer by backing it up.
Attach the front trailer to the dolly.
The pintle hook locked.
Keep the converter gear support high by securing it.
Step 5: Connect the dolly to the rear trailer — Make sure the wheels are chocked and/or the trailer brakes are engaged.
Verify that the trailer's height is accurate. The trailer is lifted somewhat when the dolly is put below because it has to be slightly lower than the center of the fifth wheel.
The rear trailer should be covered by the converter dolly. To avoid damage if the trailer moves, lift the landing gear a little bit off the ground.
Test the coupling by pulling against the pin of the number two trailer. Make a visual check of the coupling. There should be no space between the
upper (apron) and lower (platform) ﬁfth wheel, and the locking jaws should
be closed around the kingpin.
Connect safety chains, air hoses, and electrical cord.
Close the converter dolly air tank petcock and the shut-off valves at the rear of the second trailer (service and emergency shut-offs).
Open the shut-off valves at the rear of the ﬁrst trailer (and on the dolly, if so equipped).
Raise the landing gear completely on the second trailer.
Open the emergency line shut-off to check for air at the back of the second trailer before charging the trailers (by turning the trailer air supply knob in). Without air pressure, there is a problem and the brakes won't operate. There can be a closed valve or a crossed airline.
Uncoupling Twin Trailers
Step 1: Uncouple the rear trailer — Park your rig in a straight line on ﬁrm, level ground.
Apply the parking brakes so the rig won’t move.
If the second trailer doesn't have spring brakes, chock the wheels.Lower the To lighten the load on the dolly, slightly lower the second trailer's landing gear.
Close the air shut-offs on the first trailer's back (and on the dolly if so equipped).
Disconnect all dolly air and electric lines and secure them. Release the dolly brakes.
Release the fifth wheel clasp on the converter dolly. To get the dolly out from beneath the back trailer, slowly advance the tractor, first trailer, and dolly.
Step 2: Uncouple the converter dolly — Lower the dolly landing gear. Disconnect the safety chains. Apply the converter gear spring brakes or chock the wheels. Release the pintle hook on the ﬁrst trailer. Slowly pull clear of the dolly.
The techniques and steps outlined in this article apply to the most typical tractor-trailer combinations. However, there are numerous varieties of combinations and other techniques to the couple and decouple them. You are responsible for being familiar with the proper methods for coupling and uncoupling the vehicle(s) you will drive, even if they won't be described here.
Everyone driving a tractor-trailer combination must have the "nuts and bolts" knowledge of coupling and uncoupling. The detailed steps for coupling and uncoupling the most typical tractor-trailer combinations have been addressed in this chapter. You should be able to complete the coupling and uncoupling process by following the 16 coupling phases and the 12 uncoupling procedures in that sequence. You should practice the steps until they come naturally to you and you can couple and uncouple your rig "by the book" every time. This is for your safety, the safety of your equipment, and the safety of other drivers.