Self dumping trucks have advantages such as maneuverability, strong adaptability to working conditions, high labor productivity, large loading capacity, short loading and unloading time, low labor intensity, low cost and energy consumption, and good profitability. They can achieve full mechanization of loading and unloading, and are widely used in construction projects such as mining, hydropower engineering, urbanization, roads, bridges, and pipelines. Due to the harsh working environment, complex and variable working conditions, rough and difficult driving roads, frequent high-speed overloading, and high frequency of use of dump trucks, the normal operation, maintenance, and adjustment of their lifting hydraulic system are particularly important, which will directly affect the safety, reliability, loading efficiency, maneuverability, and cost energy consumption of the vehicle. Therefore, it is of practical significance to conduct fault analysis and maintenance technology research on the hydraulic lifting system of dump trucks.
1. Structural principle of hydraulic lifting system
A dump truck, commonly known as an engineering truck or dump truck, refers to a vehicle that unloads goods on its own by hydraulic or mechanical lifting. The working principle of its hydraulic lifting system is to use engine power to drive the hydraulic mechanism, that is, the engine power is output by the transmission, and the hydraulic oil pump is driven by the power take-off. The hydraulic oil is pumped to the distribution valve and pressed into the hydraulic cylinder, thereby pushing the piston to lift the cargo hopper, tilt it at a certain angle, and automatically unload it. It also relies on the self weight of the cargo compartment to reset it.
The hydraulic lifting mechanism widely used in large tonnage dump trucks currently consists of a lifting cylinder, control valve, lifting manual control valve, limit valve, and lifting oil pump assembly. The lifting mechanism relies on the lifting of the lifting cylinder to complete the lifting process. The lifting cylinder is controlled by a control valve, which is operated by the driver. In order to limit the Z-large tilt angle of the bucket and ensure that the bucket can stabilize at a certain tilt position as needed, a limit valve is installed in the hydraulic system.
The hydraulic dumping mechanism is the core of dump trucks, and its performance and quality are the primary indicators for judging the quality of dump trucks. The positioning and market positioning of lifting and dumping mechanisms are also different. When designing a lifting hydraulic system, it is necessary to comprehensively consider the power, smoothness, compactness, unloading performance, and maintenance free nature of the lifting.
2. Classification and selection analysis of lifting mechanisms for dump trucks
2.1 Main classification of dump truck lifting mechanism
Generally, dump trucks can be divided into rear tilting, side tilting, three sided tilting, and bottom unloading types according to the direction of cargo dumping. They are mainly composed of hydraulic lifting mechanisms, cargo compartments, frames, and accessories. Different manufacturers and modification manufacturers have different design concepts, and their hydraulic lifting mechanisms and cargo compartment structures are also different. The structure of the bucket can be divided into ordinary rectangular bucket and mining bucket car according to different purposes. The ordinary rectangular bucket is used for transporting bulk goods, and its rear plate is equipped with an automatic opening and closing mechanism to ensure smooth unloading of goods. The thickness of the ordinary rectangular bucket plate is 4-6mm for the front plate, 4-8mm for the side plate, 5-8mm for the rear plate, and 6-12mm for the bottom plate. The mining bucket car is suitable for transporting goods with larger particle sizes such as large stones. Considering the impact and collision of goods, the design shape of the mining bucket car is more complex and the material is thicker. For example, the standard configuration of the mining bucket car for Jiangnan Dongfeng dump trucks is a plate thickness of 6mm for the front, 6mm for the side plate, and 10mm for the bottom plate. Some models add angle steel to the bottom plate to greatly improve the rigidity and impact resistance of the bucket.
2.2 Analysis of commonly used dump truck selection
At present, foreign dump trucks are developing towards large tonnage, lightweight, diversified, and serialized directions, and more high-tech research and development are being used to develop new vehicle models, in order to shorten the design and production cycle, improve product quality, and reduce costs. With the rapid development of automotive technology and the improvement of domestic purchasing power, dump trucks are not traditional universal vehicles. In order to fully meet the strict requirements of safe, efficient, fast, convenient, and economical transportation of dump trucks, various manufacturing and modification manufacturers can develop dump trucks with different functions according to different goods, working conditions, and regions. Especially, their optimized design of lifting hydraulic systems and lifting mechanisms ensures smooth and powerful lifting, high operating efficiency, and economic fuel efficiency, which can ensure the safety and stability of dump trucks under various loads and lifting conditions.
At present, traditional lifting mechanisms such as direct push, link amplification, and link composite are mostly used for dump trucks at home and abroad. Common types of lifting mechanisms in China include T-type tripod amplification lifting mechanism, F-type tripod amplification lifting mechanism, double cylinder lifting, front top lifting, and double-sided rollover. Among them, the tripod amplification lifting mechanism is mostly used in China, which has a mature structure, stable lifting, and low cost. However, the length of the cargo body is 4.4-6m, and the closing height between the cargo body bottom plate and the upper plane of the main frame is relatively large, with a suitable load capacity of 8-40t. The closing height between the cargo body bottom plate and the upper plane of the main frame is small in the double cylinder lifting form, but the hydraulic system is difficult to ensure the synchronization of the two hydraulic cylinders, resulting in poor lifting stability and poor performance for the cargo body. The overall stiffness requirement of the bucket bottom plate is high, and it is mostly used for 6 × 4 dump trucks; Most countries in Europe, America, and other regions adopt the front top lifting method, which has a simple structure. The closing height between the bottom plate of the hopper and the plane of the main frame can be very small, and the overall stability of the vehicle is good. The hydraulic system pressure is low, making it suitable for transportation under heavy loads on highways, especially for transporting coal, mineral sand, and loose and easy to unload goods; But the front multi-stage cylinder has a large stroke and high cost; The double-sided overturning hydraulic cylinder has good force and small stroke, and can achieve double-sided overturning. However, the hydraulic pipeline design is complex, and the accident rate of lifting overturning is high.
3. Fault analysis of lifting hydraulic system
3.1 Unstable lifting or insufficient lifting angle
Fault phenomenon: The main manifestation of this fault is insufficient oil or air mixed in the oil, and the bucket cannot be lifted to the Z angle.
Fault analysis: The inlet pipe and pipeline joints of the oil pump are not tightly sealed, the rubber structural components are aging, and when replacing hydraulic components or opening the oil tank, air is easily mixed into the hydraulic system. During use, it is necessary to maintain the good performance and correct installation of the rubber sealing rings of the hydraulic system. Newly installed hydraulic components should be soaked, filled with oil, and drained; Wear and tear on the lips, elasticity? Rubber seals with reduced quantity or aging should be replaced in a timely manner; After changing the oil tank, during the initial operation or maintenance of the system, the machine needs to be started and cycled several times to exhaust the air in the system; When the bucket or lifting rod is severely deformed, it must be immediately corrected; When the rotating pair is worn and lacks lubricating grease, lubricating grease must be added; When the hydraulic oil level is insufficient, it is necessary to replenish the hydraulic oil in a timely manner; When the hydraulic oil is not clean, dirty or deteriorated, it should be replaced with clean hydraulic oil.
Before lifting the bucket, try to exhaust the air mixed into the system as much as possible; When the bucket is lifted to a large angle near Z, stop. First, loosen the air release plug on the upper part of the hydraulic cylinder slightly to release air. When the normal oil is discharged, quickly tighten the plug. If there is no oil or air discharged, it indicates that the bucket lifting angle is not enough and the oil pump needs to continue to operate at low speed until the normal oil is discharged. If the oil and air are mixed into foam shape and foam continues to appear, the compartment bucket can be placed at the deflation position for a period of time, and the air can be exhausted after the air gradually comes out of the foam, but the oil level should be paid attention to and the oil should be replenished.
3.2 After lifting the cargo box, it cannot stop in the middle
Fault phenomenon: The main manifestation of this fault is that the bucket cannot stop at any position.
Fault analysis: When there is significant leakage in the directional valve or oil cylinder, the leakage location should be investigated and the leaking component should be replaced; When reversing under heavy load, the valve stem is subjected to strong hydraulic force, causing the reversing valve to malfunction and resulting in intermittent stoppage. The reversing valve must be turned to the slow down position; When the reversing valve is not in place or stuck, it must be replaced; When the sealing of the distribution valve and return valve is not tight, the sealing components must be tightened or replaced; When the control of the one-way valve inside the hydraulic one-way valve is not strict, the one-way valve should be repaired or replaced; When the oil is too dirty, it is easy for the check valve to seal poorly, and the hydraulic oil needs to be replaced; When the viscosity of hydraulic oil is too low, it should be replaced with hydraulic oil with high viscosity; When the pipeline leaks oil, it needs to be repaired; When the manual control valve joystick is not in place, the joystick should be adjusted.
3.3 The bucket cannot be lowered after lifting
Fault phenomenon: The main manifestation of this fault is that when the bucket is in the lifting or middle position, the manual directional valve is turned to the lowering position, and the bucket cannot automatically fall.
Fault analysis: The main cause of the fault is insufficient air pressure, which cannot activate the distribution valve and return valve, resulting in the hydraulic oil in the lower chamber of the oil cylinder not being able to return smoothly to the oil tank, causing a certain negative pressure and preventing the bucket from falling. The truck should be started to reach the specified air pressure value, or the manufacturing process and disassembly methods of the distribution valve should be improved through design improvement to eliminate it; When the manual control valve joystick is not in place, the joystick should be adjusted to make it in place; Improper operation, when the lifting angle exceeds the designed Z lifting angle, it is easy to cause jamming. It is necessary to disengage the power take-off and allow the vehicle to start and move forward before braking, relying on inertia to lower the cargo body; When dumping and lifting goods on a slope, the lifting angle limit is often exceeded. At this time, it is advisable to dump on a flat road surface as much as possible; When the limit valve or safety valve fails or the limit valve pipeline is damaged, immediate repair or replacement is required; When the lifting cylinder is stuck or dented, or the piston rod is bent and deformed, it is easy to get stuck on the piston rod and affect the falling of the bucket. It is necessary to straighten the piston rod or repair the oil cylinder body; When the lifting and dumping mechanism is not used for a long time or contaminated with impurities, it may sometimes cause stagnation. It should be maintained according to regulations, lubricated, maintained or replaced frequently; When there is too much hydraulic oil in the oil tank, it can also affect the bucket to fall back. It is necessary to adjust the hydraulic oil to the normal level; When the hydraulic system is blocked by foreign objects, the foreign objects should be removed, the oil tank should be cleaned, and the filter screen should be replaced.
3.4 Do not lift when overloaded
Fault phenomenon: The main manifestation of this fault is that the cargo box cannot be lifted when the truck is fully loaded with goods, but the cargo box can be lifted normally when the truck is unloaded.
Fault analysis: When the vehicle is severely overloaded, it is extremely easy to damage the oil pump and cause deformation and damage to the transmission shaft. It must be shipped strictly according to the rated loading capacity and overloading is strictly prohibited; When the vehicle is parked on a heavily sloping slope, it should be parked in a suitable position before lifting; When the nut used to tighten the piston becomes loose, or when the piston ring of the oil cylinder is aligned, broken, or shattered, it can cause the sealing rubber ring between the piston and the piston rod to not seal tightly, resulting in oil leakage. It is necessary to tighten the piston nut or replace the piston ring or piston; When the valve stem is severely worn, hydraulic oil is prone to leakage from the valve stem, and the valve stem must be replaced and re researched; When there is a leakage fault in the lifting cylinder, valve, and pipeline, the vehicle should be stopped to investigate the leakage location and promptly eliminate the leakage point; When the connection between the main shaft of the transmission case and the oil pump is disconnected or damaged, the connection between the main shaft of the transmission case and the oil pump should be replaced again; When the oil pump body is cleaned, it is easy to strain the pump body, causing the low-pressure and high-pressure oil chambers to be connected, and the oil pressure output by the gear pump to decrease. Spray welding should be used in a timely manner to repair it to avoid premature scrapping of the oil pump; Hydraulic oil is dirty and contains many impurities, which can easily cause the control valve to get stuck. It is necessary to replace all hydraulic oil and remove impurities; When the viscosity of the oil is too low, it is necessary to replace it with a suitable hydraulic oil.
3.5 Do not lift when unloaded or overloaded
Fault phenomenon: The main manifestations of this fault are power take-off failure, lifting switch or solenoid valve failure, severe overload or hydraulic system leakage.
Fault analysis: When the connection plug of the power take-off solenoid valve falls off or the internal coil burns out, causing the power take-off transmission shaft to not rotate, the connection plug should be tightened or the solenoid valve should be replaced; When the ascending part of the bidirectional solenoid valve is damaged, emergency measures can be taken by replacing the air pipes of the ascending and descending solenoid valves, and pulling the lifting switch to the lowering position to lift the bucket. If it needs to be lowered, replace the air pipe back to its original position. However, this method should not be used for a long time to avoid accidents; When the gear pump casing is worn and the low-pressure oil chamber and high-pressure oil chamber are connected or the W-shaped sealing ring at the rear of the gear pump is punched, the gear pump or sealing ring must be replaced in a timely manner; When the nut used to tighten the piston becomes loose, the cylinder piston cracks, or the piston ring breaks or aligns, causing the sealing rubber ring between the piston and the piston rod to not seal tightly and causing oil leakage, the nut should be tightened in a timely manner and replaced? Bad piston or piston ring.
3.6 Lifting abnormally slowly or not lifting at all
Fault phenomenon: The main manifestation of this fault is insufficient oil pressure or air mixed into the oil.
Fault analysis: Corresponding treatment methods should be taken according to different situations, such as adding hydraulic oil to the specified height when the system is short of oil; When the leakage of the lifting cylinder is significant, the lifting cylinder should be repaired; When the hydraulic pipeline is damaged, it is easy to cause a large amount of leakage, resulting in severe oil shortage in the system, and the hydraulic pipeline needs to be replaced; When the lifting oil pump is severely worn or rotates in the opposite direction, it should be repaired or replaced; When there are foreign objects, loose closure, or blockages in the pipeline of the one-way valve inside the hydraulic lift valve, the one-way valve needs to be cleaned; Manual control valve joystick? When in place, adjust the gear of the distribution valve; When the viscosity of hydraulic oil is too low or deteriorates, the hydraulic oil should be replaced; When the hydraulic oil tank switch is not fully opened, it should be fully opened; When the bucket is severely overloaded and the pressure of the hydraulic system exceeds the relief pressure of the distribution valve, the relief valve begins to unload, causing the bucket to be unable to lift and requiring unloading to the rated load before lifting; When air is mixed into the hydraulic system, try to exhaust the air as much as possible; When the resistance at each pivot point is too high, it is necessary to use methods such as adding lubricating grease to each lubrication point to solve the problem.
3.7 The bucket descends on its own or descends too slowly
(1) The bucket descends on its own
Fault phenomenon: The main manifestation of this fault is that during the lifting process of the bucket, the manual reversing valve is set to the center stop position (pressure holding state), and the bucket cannot stop lifting, but instead falls back on its own; During the descent of the bucket, if the manual directional valve is set to the center stop position, the bucket cannot stop descending.
Fault analysis: The main reason for the self lowering is that there is a partial loss of pressure in the hydraulic system, and the existing pressure is difficult to overcome the self weight of the bucket, causing it to lower; Leakage inside the oil cylinder causes the hydraulic oil in the upper and lower chambers of the cylinder to communicate, and the hydraulic oil in the lower chamber cannot maintain pressure, causing the bucket to descend on its own; The pneumatic distribution valve body and valve core are not tightly sealed, resulting in partial communication of the hydraulic pipeline. The hydraulic oil in the cylinder returns to the oil tank through ports A and O, making it difficult to achieve the pressure holding effect in the lower chamber of the cylinder; The one-way valve at the high-pressure oil pipe joint of the pneumatic distribution valve is stuck or poorly sealed by foreign objects, causing the oil cylinder to fall down on its own after returning oil. It must be cleaned and blown clean with compressed air; When there are no foreign objects in the one-way valve, it may be due to poor sealing of the piston ring and other related components causing oil leakage. The nut that fixes the piston should be tightened in a timely manner, and the damaged piston or piston ring should be replaced.
(2) The descent speed of the bucket is too slow
Fault phenomenon: The main manifestation of this fault is hydraulic system blockage or malfunction.
Fault analysis: The main cause of the fault is blockage in the hydraulic system (pipelines and hydraulic components). When there are many impurities in the hydraulic oil, the troubleshooting method is to replace it with high-quality hydraulic oil; The valve core of the pneumatic distribution valve does not move properly, causing hydraulic oil in the hydraulic pipeline to be blocked when passing through the A and O ports of the distribution valve during the descent of the bucket, resulting in a certain negative pressure and affecting the descent speed of the bucket; Some moving parts are stuck or burned, and the elimination method is to remove the stuck parts and add grease in a timely manner.
3.8 When lifting, the bucket tilts or the oil cylinder is pulled out
(1) Box tilt
Fault phenomenon: The tilting fault of the cargo box during lifting is mainly manifested as the cargo box tilting to one side during lifting.
Fault analysis: When the bucket pin falls off, the bucket must be quickly lowered and returned to the warehouse for repair; When the tire is severely deflated or punctured, it is necessary to inflate the tire to standard pressure or replace the tire; When the stabilizer bar ball head breaks or the pin falls off, the stabilizer bar ball head should be replaced and the pin tightened; Truck suspension fracture is a malignant fault, and structural design should be improved to strengthen the suspension system and enhance its reliability; Lifting the cargo body on sloping ground should be avoided, and the vehicle should be parked on flat ground before lifting.
(2) Oil cylinder extraction
Fault phenomenon: The main manifestation of the cylinder extraction fault during lifting is that when lifting to the next section after Z, the bucket cannot be controlled to automatically rise.
Fault analysis: When the lifting angle of the cargo body is too small and the rear suspension is too long, the vehicle needs to be redesigned and reinstalled; When the installation position of the limit valve is incorrect, the installation position of the limit valve should be readjusted. If the cargo is a large block and the lifting angle is too small, the lifting angle must be adjusted to achieve a maximum travel angle of Z; When the fixing bolts of the bucket limit switch are loose, they should be tightened in a timely manner; The lifting limit switch is a vulnerable component with a high failure rate. When the clearance or offset of the lifting limit is too large, it can easily cause the lifting cylinder to be pulled out, which can break and damage electrical components, engines, and oil pipes, and even lead to major safety accidents. The maintenance intensity is high, the cost is high, and it seriously affects the vehicle's drivability. To avoid the malfunction of lifting cylinder extraction, the lifting operation should be stopped immediately when the bucket is lifted to the set height; At the same time, strengthen daily inspections to eliminate potential safety hazards in their early stages.
3.9 The bucket falls from the "center stop position"
Fault phenomenon: The main manifestation of this fault is that the bucket will fall down at any position.
Fault analysis: When the one-way valve of the gear pump is not tightly sealed, the gear pump and one-way valve need to be repaired; When the control valve or directional valve malfunctions, repair or replace the control valve or directional valve; When there is a leakage inside the hydraulic cylinder, causing the pressure to be unable to be maintained, the hydraulic cylinder piston and piston ring should be repaired, and the hydraulic cylinder should be replaced if necessary.
3.10 There is traction when lifting the bucket
Fault phenomenon: The main manifestation of this fault is that the vehicle has traction without exceeding the switch after unloading the ore rock.
Fault analysis: The main cause of the fault is the proximity switch and circuit failure of the cargo compartment; Some vehicles have traction after lifting, which is a normal phenomenon for GE company's vehicle safety considerations, and the speed is limited to 5mph.
3.11 The bucket does not land or lands flexibly
Fault phenomenon: The main manifestations of this fault are excessive lifting angle, hydraulic cylinder or control valve malfunction.
Fault analysis: When the lifting angle is too large, such as when a dump truck unloads on a slope and the bucket exceeds the stable point, the vehicle needs to be stopped on flat ground before lowering the bucket; When the sealing of the hydraulic cylinder head is too tight, adjust the compression nut to ensure that the hydraulic cylinder head does not leak oil; Improper installation of hydraulic cylinder bracket, readjust and reinstall; When the piston rod bends, it must be calibrated or replaced; When the lifting control valve fails and cannot return to its original position, it should be repaired or replaced; When the lifting control circuit is disconnected or the control lever is broken, the circuit needs to be repaired or the control lever needs to be replaced.
3.12 Trembling when lifting the bucket
Fault phenomenon: This fault mainly manifests as shaking during test lifting after system maintenance or replacement of high-pressure oil pipes, but rarely occurs during heavy vehicle lifting and strong lifting.
Fault analysis: During the test drive after maintenance, it is necessary to lift it repeatedly several times to eliminate the air mixed in the hydraulic system; When the power take-off or oil pump is damaged, it needs to be replaced; When the connecting devices such as the box bucket and auxiliary beam deform, they should be improved or repaired; When the flow rate of the inlet pipe changes too much, it is necessary to check the oil circuit; When the oil pump leaks internally, it should be repaired or replaced in a timely manner; When the hydraulic oil tank is short of oil, it is necessary to replenish the specified model of hydraulic oil. If the hydraulic oil is too dirty or there are many impurities in the hydraulic oil tank, the impurities in the system need to be removed. After cleaning the oil tank, a new filter screen and hydraulic oil should be replaced.
3.13 The bucket cannot tilt over
Fault phenomenon: The main manifestation of this fault is a lack of hydraulic oil in the oil tank; Oil pump and valve?? Or control the cylinder to mix air, etc.
Fault analysis: When the oil level in the hydraulic oil tank is insufficient and the bucket is in its original position, it is necessary to add enough oil to the specified value; When the circuit breaker valve is stuck, a lever should be used to adjust the valve to its original position or replace it; When the oil pump connected to the transmission cannot operate normally, the sealing degree of the oil circuit from the transmission housing to the control cylinder should be checked; When the hydraulic distribution valve does not work or malfunctions, some pipelines should be loosened, and the control cylinder should be checked for air contamination. The control cylinder needs to be disassembled for cleaning, and then a new distribution valve should be replaced.
3.14 Hydraulic cylinder, rod strain or oil leakage
Fault phenomenon: The main manifestation of this fault is the damage of oil cylinder components or the failure of seals during actual operation, resulting in the inability of the oil cylinder to work normally.
Fault analysis: When the vehicle is overloaded, the cargo must be unloaded correctly; When the clearance between the oil cylinder bracket exceeds the tolerance and the oil cylinder installation is not vertical, the bracket clearance should be adjusted properly; When lifting the oil cylinder, if the cylinder tube interferes with other components and is damaged, it needs to be redesigned and installed again; After a rollover, when continuing to use production, damaged parts related to the oil cylinder should be replaced; When unloading, if the roadbed is uneven, it is necessary to strictly follow the requirements and regulations for operation and use; When the top nut of the oil cylinder is loose, tighten the top nut of the oil cylinder according to the torque; When the clearance between the oil cylinder ear shaft and the bracket hole is too large, the damaged components should be replaced; When the hydraulic oil is dirty, the oil filter element and hydraulic oil must be replaced.
When the vehicle experiences multiple instances of uneven loading, it is necessary to load the goods correctly and replace the sealing kit; When the cylinder is pulled, the cylinder and sealing kit need to be replaced; When the installation position of the oil cylinder does not meet the requirements, the cylinder barrel should be replaced and the position of the oil cylinder should be readjusted; Avoid illegal operations and do not drive while lowering the oil cylinder; Seals are prone to accelerated aging and failure in high-temperature environments, and it is necessary to replace oil seals or sealing rings in a timely manner; When the air filter of the fuel tank is dirty, the air filter must be replaced; When the air port of the oil cylinder overflows, if the oil level in the tank exceeds the level gauge, a small amount of oil can be drained from the tank; When the hydraulic oil model is incorrect, the appropriate hydraulic oil should be replaced.
3.15 Pneumatic control valve or limit valve stuck
Fault phenomenon: The main manifestation of this fault is the sudden failure of the pneumatic control valve or limit valve.
Fault analysis: When impurities are mixed into the pneumatic valve, the valve should be removed or replaced; When the limit valve core fails, the limit valve needs to be replaced; When the trachea is damaged and leaking, tighten the joint or replace the trachea; When there is a bending phenomenon in the trachea, it is necessary to rearrange the direction of the trachea.
3.16 Oil pump leakage, non rotation or burning damage
Fault phenomenon: The main manifestations of this fault are increased oil pump noise, insufficient or no hydraulic system pressure, insufficient or no oil pump displacement, and high temperature.
Fault analysis: When the bucket falls too quickly under heavy load, the oil chamber pressure is too high, or the spline shaft scratches the self tightening oil seal at the oil pump shaft neck, it is easy to damage the oil seal and cause leakage; Due to uneven stress on the "O" - shaped sealing ring between the oil pump and the transition plate, leakage may occur, which can also increase the noise of the oil pump and lower the pump oil pressure. Therefore, caution must be taken when installing the journal oil seal to ensure that the pressure in the low-pressure chamber is within the rated range; When the fastening bolts between the oil pump transition plate and the distribution valve become loose or the sealing ring is damaged, there is a significant leakage, and the sealing ring needs to be replaced and tightened; When impurities are mixed into the joint surface, it is usually possible to tighten the high-pressure side bolts, replace the sealing ring, clean the 2 mating surfaces, and then apply sealant.
When the sealing ring inside the oil pump is damaged or the input shaft end skeleton oil seal is damaged, spare parts must be replaced; When the input end bearing of the gear oil pump is loose and causes scratches on the pump body and gears, the bearing needs to be replaced and the scratched part of the pump body needs to be ground; When the oil seal of the drive shaft skeleton of the gear oil pump is damaged, causing oil leakage at the drive shaft, a new skeleton oil seal should be replaced; When the sealing surface of the oil outlet flange is poor and the sealing surface and sealing ring are damaged, they need to be repaired or replaced; When the sealing surface of the joint between the back cover and the shell is poor and leaks oil, it is necessary to check whether the sealing surface has scratches, burrs, deformations, dirt, etc., and make appropriate adjustments; When there is abnormal noise or low pump oil pressure in the oil pump, timely maintenance or replacement should be carried out.
When the oil pump transmission mechanism or gear shaft sleeve is damaged, unable to operate, or has serious internal leakage, spare parts must be replaced immediately and repaired; When the connecting sleeve between the oil pump and the power take-off breaks, the connecting sleeve must be replaced; When the oil pump stagnates or the power take-off malfunctions, it is necessary to repair or replace the oil pump or power take-off; When the power take-off operating system malfunctions, timely maintenance should be carried out; When the hydraulic oil is insufficient, dirty or severely deteriorated, it should be replenished or replaced with clean hydraulic oil in a timely manner; When the oil pump runs without load for a long time and is not working, the power take-off is required to shift off.
3.17 Insufficient oil absorption or inability to absorb oil
Fault phenomenon: The main manifestation of this fault is that the hydraulic system is slow or unable to rise and fall (advance and retreat); During the lifting (advancing and retreating) process, the hydraulic system pressure is unstable or produces noise, and bubbles appear in the oil tank; Gear pump damage or sudden increase in oil temperature.
Fault analysis: The suction pipe is too thin or too long, with blind spots at the bend. If there are too many bends, the suction pipe must be thickened or shortened to prevent blind spots and reduce bends during bending; When there is a leak in the oil suction pipe, it is necessary to identify and address the leak; The oil suction filter and oil suction pipe are blocked. Clean the filter and remove the blockage; When the oil level in the fuel tank is too low or there is no oil, it is necessary to add oil to the specified height; When the viscosity of the oil is too high, hydraulic oil recommended by the manufacturer should be used; When the sealing surface of the oil suction flange is poor, it is necessary to check whether the sealing surface is deformed, burrs, scratched or dirty, and make appropriate corrections; When sucking air from the active shaft neck skeleton oil seal of the gear pump, it is necessary to remove the gear pump, check whether the skeleton seal is damaged, and replace the skeleton seal if necessary.
3.18 No load noise or hydraulic system whistling
Fault phenomenon: The vehicle's empty load noise fault is mainly manifested as slow sinking of the cargo compartment when the vehicle is empty, and intermittent noise will be produced, but this phenomenon is normal. What are the main causes of hydraulic system whistling faults? When the vehicle is overloaded excessively, it will cause the system pressure to be too high, the safety valve to open, and accompanied by a sharp whistling sound.
Fault analysis: The main cause of the no-load noise fault is the small clearance between each transmission shaft and the shaft sleeve, insufficient lubrication, and high friction force, which causes the vehicle to sink intermittently and produce intermittent sliding and noise due to friction. This type of fault will gradually disappear automatically after the sliding surface is fully lubricated during use.
Other sounds usually occur when the oil pump is overloaded and must be operated with reduced load. If the handling load capacity is appropriate, it may be due to the low set pressure of the safety valve causing it to open, and the opening pressure can usually be adjusted according to regulations.
4. Conclusion
The lifting hydraulic system is a key working system of dump trucks, and its performance is superior?? The main performance indicators of the vehicle are affected by its faults, which involve the vehicle's driving safety, transportation function, and self unloading function. The quality of its working condition is related to the vehicle's work efficiency and project progress. Therefore, in-depth research on the analysis and control technology of hydraulic system faults in dump truck lifting can significantly improve the operational efficiency, integrity rate, and maneuverability of the vehicle.
2025 September 4th Week VAFEM Product Recommendation
Clutch Release Bearing by VAFEM. Length: 1.9690". Outside Diameter: 3.1100". Inside Diameter: 1.7380". If you’re looking for premium-quality replacement automotive parts to keep your vehicle performing reliably, you can’t go wrong with superior-grade VAFEM products. Made using the finest materials and the latest manufacturing techniques, these parts deliver outstanding strength and wear resistance. They will serve you reliably year in and year out, ensuring a safe driving experience.
https://www.vafem.com/products/Truck-Clutch-Bearings/850.html
2025-09-26