What is a semi-trailer?

What is a semi-trailer?

A truck semi-trailer is an unpowered vehicle connected to a tractor (front) through a saddle. It has no front axle and part of its weight is carried by the tractor. It needs to be used in conjunction with the tractor. Compared with full trailers, semi-trailers have higher stability, load-carrying capacity and flexibility, and are the main equipment for modern road transportation.

Common categories and application scenarios of truck semi-trailers

Categories & structural features & applicable scenarios

• Dropside semi trailers---metal fences that can be opened and closed on three sides

  commonly used in the transportation of building materials (such as steel and wood) and the loading and unloading of agricultural and sideline products, and are suitable for bulk cargo scenarios that require manual loading and unloading.

• Fence semi trailers---top closure + removable fences on both sides

  commonly used in express logistics and daily necessities transportation, taking into account the needs of rainproof, anti-theft and fast loading and unloading.

• Flatbed semi trailers---full flat cargo platforms without fences

  are commonly used in engineering machinery (such as excavators) and container transshipment, and are suitable for the transportation of extra-wide, extra-high or non-detachable heavy equipment.

• Container semi trailer---special chassis with twist lock fixing device

  commonly used for multimodal transport of containers from port terminals to inland, supporting 20/40-foot standard containers and refrigerated containers.

• Tank semi trailer---cylindrical/elliptical closed tank

  commonly used for liquid transportation (oil products, chemical raw materials), powder and granular materials (cement, grain), and hazardous chemicals that need to prevent leakage and pollution.

• Refrigerated Box semi trailer---insulated compartment + independent refrigeration unit

  commonly used in cold chain logistics (meat, pharmaceutical products), the temperature in the compartment can be controlled at -25℃ to +15℃, with a fluctuation of ±1℃.

• Car carrier semi trailer---double-layer/three-layer liftable deck design

  commonly used for bulk transportation of commercial vehicles such as sedans and SUVs, and can load up to 8-12 passenger cars at a time.

• Lowbed semi trailer --- ultra-low cargo platform (height <1 meter from the ground)

  commonly used for large-scale transportation (wind turbine blades, transformers), with a maximum load of up to 100 tons, requires a hydraulic axis system.

• Dump trailer-Hydraulic lifting mechanism

  commonly used to transport sand, concrete, garbage, ore, corn, etc.

Precautions for using truck semi-trailers

Compliance loading

• Overloading and over-limit are strictly prohibited, and must comply with the provisions of the "Road Vehicle Outline Dimensions, Axle Load and Mass Limits"

• Container semi-trailers need to check whether the rotary lock is completely locked, and tank trucks transporting hazardous chemicals must hold a "Road Transport Permit"

Safe driving

• Reserve a larger radius when turning (the inner wheel difference of a semi-trailer can reach 3-5 meters)

• Reduce speed when driving without load (high center of gravity is prone to rollover), avoid sudden braking in rainy and snowy days

Cargo fixing

• The flatbed truck needs to use straps + anti-slip pads to fix the cargo, and the spacing should not exceed 2 meters

• Flatbed truck Transport equipment needs to weld thrust baffles and use ratchet tighteners to fix at multiple angles

Connection inspection

• Check the wear of the saddle and the sealing of the air pipe circuit joints every day

• The gap between the traction pin and the saddle should be less than 3mm, and the grease application cycle should be ≤15 days

Maintenance methods and cycle recommendations

Project & operation points & cycle

• Tire maintenance---tire pressure monitoring (standard value ±10%), regular rotation (every 10,000 kilometers), removal of pattern stones---daily inspection before driving

• Braking system---check the brake air chamber push rod stroke (standard value 25- 40mm), replace the filter element of the drying tank---every 3 months or 50,000 kilometers

• Lubrication system---apply lithium-based grease to the traction pin and leg gear, and add high-temperature grease to the wheel hub bearing---every 5,000 kilometers

• Electrical system---check the waterproofness of the taillight circuit, and anti-oxidation treatment of the battery electrode---full inspection every month

• Body maintenance---clean and disinfect the refrigerated truck body, and high-pressure washing inside the tank (acid and alkali liquids need to be neutralized after transportation)---after each unloading

• Chassis inspection---tighten the U-bolts (torque standard: 450 -500N·m), detect cracks in the frame longitudinal beam (magnetic particle inspection)---every 6 months

Special scene operation suggestions

• Large-piece transportation: plan the route in advance (avoid height-restricted bridges), and apply for an overload transportation license

• Hazardous chemical transportation: equip with gas masks, adsorbent cotton and other emergency supplies, and the static grounding resistance of the tank is ≤5Ω

• Cross-border transportation: prepare CIM/SMGS international railway waybills, and check the differences in axle weight limits in various countries

Proper use and scientific maintenance can extend the service life of semi-trailers to more than 10 years and reduce maintenance costs by 30%!