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The use and maintenance of parts for trailers

Oct 24, 2019

The use and maintenance(system) of  parts for trailers 

1. Use and maintenance of suspension

1.1 Every six weeks or two weeks after the first new vehicle is driven, it should be lubricated frequently under severe conditions;

1.2 Fill a small amount of grease on the sliding end of the sliding part and the leaf spring, see the following figure;


Picture 3-1-1


1.1 Regularly check the fasteners (two to three times a year) (the two-axis leaf springs are shown in the figure below, and the three-axis leaf springs are the same).


Picture 3-1-2

Preload torque of the bolt:

· Balance beam bolt                M30 x 2 through the split pin, opening

· Pull rod shaft nut                 M14 120-160N.m

· Adjustable lever lock nut          M16 189-252N.m

· Spring retaining bolt              M16 through the split pin, opening

· U-bolt                          M24 x 2 680-850N.m

1. Use and maintenance of lifting legs

2.1 The semi-trailer must be parked on a flat concrete pavement or a solid flat ground. It is not allowed to support the semi-trailer on the slope or on the soft soil surface using the support device;

2.2 It is not allowed to exceed the lifting height. When the lifting height is not enough, the lower end of the leg can be padded to the appropriate height with a rectangular sleeper, see the figure below;


2.3 When lifting, lift the semi-trailer to the appropriate height: firstly ground the support base with high-speed gear, then lift it with low-speed gear, and after the support base is grounded, turn 4-8 turns (to make the semi-trailer support reliable) )

2.4 Lubrication of the inner leg: the inner leg of the oil storage cylinder, the screw rod and the nut are self-lubricating and maintenance-free, the screw rod and the nut movement pair of the oil storage cylinder are not installed, and the bearing is filled twice a year or as needed. , turn the handle to extend the inner leg repeatedly and take it back several times;

2.5 Lubrication of the outer leg: The bevel gears in the left and right outer legs are filled with grease twice a year or as needed, and the gearbox is lubricated; the gears in the gearbox are filled with grease twice a year.

3. Use and maintenance of the traction pin

When the vehicle is in use, the traction plate and the traction pin should be coated with sufficient general-purpose lithium-based grease to ensure reliable lubrication. The traction pin should be regularly maintained and checked for bolt tightness and neck wear of the traction pin. 2′′ towing pin When the neck is worn to 49mm, the 3.5′′ traction pin neck should be replaced with a new one when it is worn to 86mm.

For the assembled traction pin, the coupling bolt is for one-time use, and the coupling bolt must be replaced at the same time as the traction pin is replaced.

* The towing pin is a type A safety device connected to the transportation vehicle. Please follow the installation instructions below.

4. Use and maintenance of pneumatic system

4.1 Brake system and its operating device

The semi-trailer adopts a double-line pneumatic brake system, and the service brake system mainly comprises a gas joint, a gas supply pipeline, a control pipeline, an emergency brake valve, a gas storage cylinder, a brake air chamber and a wheel brake.

     The following figure is a schematic diagram of the two-line and three-axis semi-trailer dual-line brake system.


Picture 3-4-1 Schematic diagram of three-axis semi-trailer brake system

1-Control pipe line 2-Supply pipe line 3-Control gas joint 4-Brake chamber

5-Emergency relay valve 6-Air reservoir 7-Drain valve 8-Manual valve


Figure 3-4-3 Schematic diagram of single axle semi-trailer brake

1-Control line 2-Supply line 3-Control gas joint 4-Brake chamber

5-Emergency relay valve 6-Air reservoir 7-Drain valve 8-Manual valve

4.2 Brake device inspection

4.2.1 Check the entire pipe and joint

A.Check the pipes and joints for cracks and damage, and repair or replace them if necessary.

B.Connect the semi-trailer brake pneumatic system and the traction brake pneumatic system.

C.Increase the air pressure to 650-750 kPa and check the pressure from a pressure gauge installed in the tractor cab or air supply line. Pressure

D. Depress the brake pedal of the tractor and check if the force drop within 30 minutes exceeds 29.4 kPa (when the engine is not working).

E.If the pressure drops beyond the 29.4 kPa standard, check the leaking area with soapy water, and if it leaks, tighten the part or replace the part.

4.2.2 Checking the emergency brake valve

a The gas connection of the gas supply line is checked for automatic braking. If the automatic braking is not possible, the emergency brake valve is faulty.

b There is no air leak in each part of the emergency brake valve.

c Check if the exhaust gas is removed from the exhaust port when the brake is released, and if so, it is normal.

d If the action is not working, replace the entire emergency brake valve.

4.2.3 Checking the air reservoir

     After each trip is completed, be sure to unscrew the drain valve at the bottom of the air reservoir to drain the condensate. When draining, the internal gas will be discharged at the same time. If the emergency brake valve is operated when the exhaust is too much, it should be re-inflated to keep the pressure in the cylinder at the specified value.

5. The use and maintenance of the circuit system

5.1 Circuit System Principle

The semi-trailer has an international standard circuit system suitable for the tractor. The front wall of the car has an electrical connection socket. The rear part of the car body is provided with a brake light, a turn signal, a reverse light, a license plate light, a fog light, and a rear display. Profile lights and triangular reflectors; the front end of the car body is provided with front position lights and front position lights; the side of the car body is provided with a plurality of side indicator lights (one of which is a side turn signal), and the voltage is 24V DC. The following figure shows the schematic diagram of the semi-trailer circuit system.


5.2 Color of the wiring harness of the circuit system


Contact number


Wire color


Common circuit



Right front position light, right   side light, license plate light, right rear position light



Right rear turn signal



Brake light



Left rear turn signal



Left front position light, left side   light, fog light, left rear position light



Reversing light


5.3 Daily maintenance

5.3.1 Check the joint for slack, whether the wire is sagging or damaged, and repair or replace if necessary.

5.3.2 Check the lamp. If the lamp breaks, the rupture and the surface gloss are damaged, it should be replaced.

6. The use and maintenance of the axle

6.1 Use of axles

a shall not exceed the specified maximum allowable axle load and vehicle speed;

b The goods in the carriage shall not be placed unilaterally or improperly;

c must use the specified rims and tires;

d tire pressure must reach the specified value;

e driving mode must adapt to the road surface conditions;

f brakes can not overheat, otherwise it will reduce the braking performance;

g The brake should not be used immediately in the hot state. This is because the brake drum will cause cracks in the brake drum during the subsequent cooling process when it is braked in a non-uniformly expanded thermal state.

h On the train, in order to ensure safe driving, the air brakes of the tractor and the trailer must be coordinated before driving.

62  Lubrication and maintenance instructions

    Identification symbol   O lubricating     □ maintenance

    Lubricating grease: According to the requirements of the axle supplier

First   time driving

Every   15-30 days depending on usage

Every   three


every   half year

Every   150,000 km or one year or when changing brake pads

O lubricating

1 brake camshaft bearing interior



2 clearance adjustment arm


3 Replace the hub bearing grease, only use the   required grease


□ maintenance

[1] Check if the wheel nut is tightened


[2] Check the brake gap by pulling the   gap adjustment arm

[3] Check the brake lining (brake lining)   with a thickness of not less than 5mm

[4] Check the rotation of the hub bearing   and adjust if necessary

[5] Check if the hub cap is tightened

Check tire uneven wear

 Visually inspect all components for damage   and wear

Special conditions of use

When the mileage of the vehicle is small:

When the vehicle is driving under harsh working   conditions:

Maintenance is done at intervals

Maintenance cycle should be shortened   accordingly

* After the first load or after each wheel change

** Lubricate the brake camshaft bearing before operating the brake after a long stop

6.3 Brake adjustment

Operate the brake chamber, check the working status of the brake adjustment arm, and check whether the stroke of the push rod is normal. If the stroke is too large, the gap between the brake shoe and the brake drum is too large, and should be adjusted as follows:

a When adjusting the brake, first turn the adjusting bolt to the right until the adjusting shoe contacts the brake drum, then rotate the adjusting bolt to the left until the idle stroke of the adjusting arm (when the arm length is 127 mm) is 10-15 mm (see The following figure).


Figure 3-6-1

B. Check the rotation of the wheel and the wheel must rotate freely.

C. Since it is not easy to ensure the same clearance when adjusting the wheel brakes, the brakes after adjustment are not subject to the deviation.

6.4 Adjustment of axle bearing clearance (subject to the axle manual)

A. jack up the semi-trailer.

B. Rotate the rim, tighten the lock nut with a torque of 400 N.m, and then reverse the screw 1/8-1/6 rpm.

C. Rotate the rim and gently tap the hub (bearing position) to check whether it rotates smoothly. If the resistance is large, loosen the lock nut slightly until the rim can rotate freely without obvious swing. Then insert the opening. Pin to lock the lock nut.

D. Apply sealant to the wheel cover and install the wheel.


7. Use and maintenance of tires

7.1 Tire pressure and maintenance

Whether the tire pressure is suitable or not greatly affects the life and safety of the tire, so the tire pressure should be maintained, including the spare tire, and all tires should have the same inflation pressure. Pressure measurements and adjustments should be made while the tire is cold.

7.1.1 Insufficient inflation pressure will cause damage to the tire from the following aspects:

A. tire life is shortened

B. tire wear acceleration, especially the abnormal wear of the shoulder

C. curtain is cut and separated from the rubber

D. sidewall will rupture

E. fuel consumption increased

F. When driving at high speed (more than 100km/h), due to the centrifugal force, the tread pattern is dropped.

7.1.2 When the inflation pressure is too high, it will result in:

A. mechanical failure or other failure

B. side slip

C. cut or puncture

D. wear of the tread center is accelerated

The relationship between tire pressure and ground contact area after inflation is shown in the figure below:


7.1.3 Precautions when inflating:

A. new tire tends to swell during a specific initial period of use, whic Inflation pressure is too large

h will result in an increase in the volume of the tire and a decrease in internal pressure. It is therefore recommended to inspect the tyres frequently during the first 3,000 km.

B. Pay attention to leaks. If there is a leak, the new valve core should be replaced and the valve cap should be refilled if it is lost.

C. When using twin tires for normal driving, the air pressure must be within the range of correct inflation pressure (0, -50) KPa.

D. Check the pressure before using the spare tire.

7.2 Impact, maintenance of road surface and brake on tires

a. The tires are worn differently depending on the load, road surface and braking state. To extend the life of the tire and improve safety performance, the tire installation position should be exchanged regularly (5000 km per trip) (see the figure below).


Figure 3-7-2 Position and sequence of regular          Figure 3-7-3 Location and sequence of

regular exchange of tires for three-axle vehicles         exchange of tires for two-axle vehicles




b. Check the looseness of the wheel nut every day. If it is loose, tighten it according to the diagonal method and the specified torque. After the new car or the replacement of the steel ring, pay attention to the wheel nut during the first loading, and tighten all the wheel nuts according to the specified tightening torque when driving about 50Km.

c. Do not change the original model of the tire and rim without authorization. Do not change the type of tire bolts without authorization.

d. The life of the tire depends largely on the size of the load. Therefore, it is important to properly control the relationship between the load and the tire pressure. Overloading will result in excessive sidewall deformation and increased cutting probability; excessive tread movement will accelerate wear and abnormal wear; increase fatigue of rubber and cord, and weaken the adhesion between rubber and cord.