Frequent coupling and uncoupling is a routing part once operating articulating vehicles (buses, truck-trailer). Coupling procedures can be vary based on the specific vehicle and location.
By following the correct procedure, operator can perform coupling & uncoupling safely and effectively.
Before start the coupling, operator must inspect the fifth wheel condition, trailer skid plate and king-pin.
- Check the lubricant grease condition of the top of the fifth wheel (if required apply recommended EP grease on the top surface of the fifth wheel)
- Locking and releasing mechanism should be inspected properly. (lubricate dry components)
- Ensure fifth wheel is titled down to the rear
- For sliding fifth wheels, ensure sliders are properly locked in the correct position. (if its air operated, check the airlines)
- Check all the airlines and power connectors. (no damages, uneven bends)
- Open the fifth wheels’ locks, if its closed.
- Ensure trailer skid plate and king-pin is free from dust, rust and damages.
Coupling to the trailer
- Release the parking brakes of the tractor and slowly reverse tractor to trailer.
- Trailer and the tractor must be in the straight line as much as possible.
- When the tractor comes to the slightly under the trailer, stop the tractor and apply the parking brakes in the neutral position.
- If it’s an air suspension tractor, release the air from tractor suspension to adjust the height.
- Ensure fifth wheel is lower the trailer skid plates.
- Adjust the trailer height with landing gears if necessary.
- Place the wheel chocks to trailer wheels if it’s a slippery surface or trailer doesn’t equipped with trailer brakes.
- Release the tractor parking brake and reverse slowly in straight line to the trailer
- Feel or listen the sound when the fifth wheel attachment to the king-pin locked position.
- Put lowest forward gear and release the clutch smoothly in engine idling. If fifth wheel not engaging properly, tractor will move forward. (this operation is also known as the tug test)
- Exit the tractor and visually inspect the fifth wheel locking mechanism is in proper closed position. Trailer skid plate and fifth wheel top surface should be engaged with zero gap.
- Connect the electrical lines and the air lines
- Raise the landing gears to their original position. Remove the wheel chokes if used.
- Check the air gauges and ensure all in normal operating condition.
- Drive forward slowly and check the service brakes are operating properly.
Now the tractor and trailer is safe to start the journey.
Failure of proper couple of tractor & trailer, can be result to separation. It can be result to sever damage and death injury.
Uncoupling from the trailer
- Park the tractor and trailer in a suitable place for uncoupling
- Apply the trailer brakes
- Reverse slowly to small distance to relieve the load of fifth wheel locks
- Apply the tractor parking brakes
- Lower the landing gears and chock the trailer wheels for better safety.
- Disconnect all the air and power lines from trailer
- Unlock the fifth wheel lock by pulling the release handle. If its equipped with air release pull and hold the release valve until get unlocked.
- Move the tractor slowly to front for 1.5 feet to disengage the fifth wheel from trailer
- Visually inspect the fifth wheel and king pin for uncoupling and ensure trailer is mounted in landing gears.
Now tractor can be move out from trailer safely
Don’t raise the trailer more than the height of fifth wheel by landing gears. It can be damaged the locking mechanism of fifth wheel.