The causes and maintenance of common faults of dump trucks

(1) It is difficult to lift the carriage. The main reason is the insufficient fuel in the fuel tank. One is that the fuel tank filter screen or pipeline is severely clogged; The oil pump is faulty. No fuel supply; The lift switch (for air access) is blocked, and the return oil valve of the distribution valve is stuck at the position of the return oil valve. The relief valve is seriously out of balance, and the high-pressure oil pump is leaking. The lifting cylinder and the limit valve are stuck, causing the gas path to the main distribution valve to remain connected for a long time. And the air pressure in the air storage tank is insufficient; The gears of the power take-off and oil pump are not working properly. It is caused by unclean hydraulic oil and impurities jamming the distribution valve, etc. When making a judgment, if the pipelines in the hydraulic system are blocked, it is necessary to check whether the oil inlet, return oil port and the oil tank filter are blocked. If the hydraulic oil is too dirty, it should be replaced with new oil. Check if the oil passage is unobstructed by cleaning the filter screen. The second issue is the severe wear of the distribution valve stem, which increases the fit clearance between the valve stem and the inner hole of the valve body, causing the high-pressure oil pumped by the gear pump to leak back into the oil tank through this clearance. At this point, it should be replaced and re-paired for grinding.

(2) The carriage is lifted slowly and weakly with some jolting. If air enters the hydraulic system, it is usually due to an unobstructed return oil circuit and excessive frictional resistance of the lifting cylinder. The limit valve of the lifting cylinder is not tightly sealed or out of balance, the sealing ring of the lifting cylinder is not tightly sealed, the working efficiency decreases after wear, the oil volume in the oil tank is insufficient, the gear pump fails to reach the specified oil discharge volume, and the pipeline is severely blocked or has leakage, etc. First, observe whether there are a large number of bubbles overflowing from the liquid surface when the hydraulic oil tank is opened. Then, tighten all the joints of the oil inlet pipeline of the gear pump. Check again for any cracks or damages in the oil pipe, clean the hydraulic oil tank and filter screen, then loosen the nut of the oil inlet pipe of the hydraulic cylinder to release the air, and try lifting the cargo box to see if the air is released. Otherwise, it may be that the oil seal of the hydraulic oil pump is leaking air. Replace the oil seal if necessary.

(3) It cannot be lifted under heavy load. Most of them are severe overloading. The vehicle was parked on a severely sloping dilapidated road ahead. The viscosity of the oil is too low. It is also caused by leakage faults in pipelines, valves and cylinders.

(4) The carriage will fall down by itself after being lifted. It is mostly due to the one-way valve being stuck. The sealing ring of the lifting cylinder is poorly sealed. The distribution valve is stuck and not fully in place. And there is a leakage in the pipeline.

(5) The carriage does not descend. Insufficient air pressure prevents the distribution valve from returning oil. Or the limit valve pipeline is damaged, or the lifting switch and the lifting cylinder are stuck.

(6) The carriage cannot be lifted at any position. It is mostly caused by the oil being too dirty, resulting in poor sealing of the check valve, or poor sealing of the distribution valve and the return oil valve.

Precautions for Troubleshooting and Repairing Faults in Dump truck Operation System devices

When encountering faults in the operation system equipment of dump trucks and conducting maintenance, first check if there is sufficient oil level. If not, add oil as per regulations. Check whether the power take-off control mechanism is working properly; Check for any leakage in the oil and gas circuits. If necessary, also inspect whether they are blocked. Check whether the oil pump, distribution valve, limit valve and other components are working well, and whether the lifting cylinder is well sealed. Repair them if necessary. If the various control valves of the control system malfunction, new parts should be replaced. When the hydraulic oil is not clean, causing blockage in the oil passage or insufficient hydraulic pressure, slow movement, or the vehicle compartment cannot be lifted to the full position, the hydraulic oil should be replaced. When the transmission mechanism or gear shaft sleeve of the oil pump is damaged, cannot operate or has severe internal leakage, the parts should be replaced and repaired.

When the journal and bearings of the driving and driven gears of the oil pump wear out, the meshing clearance will increase, resulting in a decrease in the oil pump's displacement, a decline in operational smoothness, and noise generation. After the wear of the journal and bearings, the radial clearance between the gears and the pump cavity will also change, causing the center of the gears to shift towards the oil inlet cavity relative to the corresponding centerline of the pump cavity. During operation, radial runout is prone to occur, and some areas will become larger while others will become smaller. Large clearance causes leakage, resulting in a decrease in the flow rate and pressure of the oil pump. However, those with small clearances will cause the tooth tops to collide and rub against each other, leading to damage to the pump cavity. Wear, scratches and grooves on the end face of the gear and the end cover or end face bearing of the pump body will cause leakage in the oil inlet and outlet chambers inside the oil pump, increase the circuit size, and thus increase the amount of oil leaking from the oil outlet chamber and the oil chamber, resulting in a decrease in the pressure and flow rate of the oil pump. Upon discovering the faults caused by the above-mentioned erosion damage, after identifying the cause, replace the parts and repair them in a timely manner.

The maintenance mainly involves braking, hub bearing oil, engine oil, gear oil for the transmission and rear axle, as well as grease for all the moving joints of the vehicle.

Brake and hub bearing oil are maintained together. This is basically done every time a secondary maintenance is carried out, that is, once every three months.

2. Engine oil is basically changed based on the mileage driven. Generally, it is changed every 8,000 kilometers or so. It is fine to change it to Kunlun CF grade or CH grade. As for tires, there is no fixed replacement time. We usually change them when they are broken or when the tread is very shallow.

3 The gear oil of the transmission does not need to be changed frequently. Generally speaking, it is sufficient to change it every half a year or half a year. The gear oil of the rear axle can be changed more often. If it has been driven for a long time without much rest, it is best to remove the rear axle for maintenance and clearance every three months.

4. There are many benefits to frequently adding grease to dump trucks. Personally, I think it is necessary to add grease at least once a month. If possible, add it twice. The main reason is that the pins of the hydraulic cylinder, the steel plate pins, and the vertical pins in the direction wear out a lot, so grease should be added frequently.