Common troubleshooting of the working hydraulic sy

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Common troubleshooting of heavy dump truck operation and hydraulic system

common failure cause analysis of heavy dump truck

common failure cause analysis method of heavy dump truck is as follows:

1 Power takeoff failure. When the power take-off of a heavy dump truck breaks down, the most direct and obvious result is that the gear pump does not rotate, the hydraulic dump system loses its power source, and the whole system is paralyzed and unable to work. Pneumatic power take-off is often used on heavy dump trucks, which is mainly composed of transmission mechanism, connection mechanism and control mechanism. The most common failure in these three parts is the control mechanism, which uses the solenoid valve to switch the air circuit. The solenoid valve controls the control cylinder of the power take-off, so as to complete the engagement and disengagement of the power take-off. During the unloading process, the solenoid valve should act frequently, and its parts are vulnerable to loss, accounting for 15.56%. Therefore, the effectiveness, sensitivity, circuit safety and switch of the solenoid valve should be checked frequently. If the circuit is normal, the working condition of the power take-off cylinder should also be checked, whether there is airtight or air leakage. If necessary, the power take-off cylinder should be disassembled for inspection. The transmission mechanism and connecting mechanism should also be maintained frequently. When the gears of the transmission mechanism mesh poorly and the connecting bolts between the shift fork and the push rod are loose, the traditional manufacturing hetero electro-hydraulic servo universal testing machine, which is still labor-intensive, often makes a constant sound when running under high load. Check the fastening bolts of each component, pay attention to the lubricating oil, clean up the dirt in time, keep each component clean and intact, and prevent bumps and scratches. In addition, the connecting bushing between the power take-off and the oil pump should also be checked frequently. If it is not firm, damaged, removed or broken, it should be replaced in time

2. Oil pump drive shaft failure. The deformation or damage of the oil pump transmission shaft of a heavy dump truck can make the dumping mechanism completely ineffective. The reasons are generally the following: the power take-off is not disengaged when the vehicle is driving. Due to the long-term high-speed operation of the hydraulic oil pump, the oil temperature of the hydraulic oil rises rapidly. On the one hand, the oil seal of the oil pump will be burned and the oil pump will "burn to death". Another serious consequence is that the centrifugal force of the gear of the oil pump will increase, and the transmission shaft of the oil pump will be deformed and damaged under the action of this excessive centrifugal force; When the vehicle is lifted with full load, the operation is too fierce. If the clutch pedal is forcibly lifted, the power take-off, oil pump transmission shaft and oil pump itself will cause great impact load due to the sudden engagement of the system, which is most likely to cause damage to the transmission shaft. When the engine is running at high speed and the temperature is low in winter, the viscosity of the oil in the hydraulic cylinder is larger, and the loss caused is more prominent; The transmission shaft will also be deformed and damaged if the installation clearance of the transmission shaft is too small, the dynamic balance of the oil pump is poor, the oil circuit is blocked, and the transmission shaft is seriously overloaded. When the transmission shaft of the oil pump is deformed or damaged, it should be repaired and replaced in time. Pay attention to avoid damage to the transmission shaft at any time during work. For example, when preparing to drive after unloading, disconnect and confirm that the power takeoff has been disconnected before driving; At the beginning of full load lifting, when the joystick is raised to the lifting position, the operation should be stable and the action should not be rough. Slowly release the clutch pedal to make the oil pump run and the carriage rise slowly; During the falling process of the carriage with load, do not pull the distribution valve to the lifting position, which is very easy to cause strong impact and premature damage to the transmission shaft; In addition, always check whether the installation clearance of the transmission shaft meets the requirements and whether the engagement length between the transmission shaft and the universal joint fork is appropriate

3. Leakage

leakage and sealing of oil pump. Two self tightening oil seals are installed at the oil pump Journal of the heavy dump truck. If they are scratched by the spline shaft, or the carriage is overloaded and drops too fast, the oil seal will be damaged and leak; In the oil pump integrated with the pump valve, the O-shaped seal ring between the oil pump and the transition plate sometimes leaks due to uneven stress, increasing the noise of the oil pump and insufficient pressure. Therefore, be careful when installing the journal oil seal. In the oil pump integrated with the pump valve, the seal ring is used between the oil pump transition plate and the distribution valve, and the bolts are fastened. There are many leaks here, because the bolts are loose, the seal ring is damaged, and there are impurities on the joint surface. Generally, tighten the bolts on the high-pressure side, replace the seal ring, clean the two mating surfaces, and apply sealant

leakage and sealing of distribution valve. The leakage of the distribution valve is mainly concentrated at both ends of the valve rod and the cone of the check valve. Check the wear of valve rod and valve body frequently to keep the fitting clearance within an appropriate range. If you want to replace the O-ring at both ends of the valve rod, pay attention to the uniform force, moderate tightness, and do not scratch the valve rod

leakage and sealing of hydraulic cylinder. Between the hydraulic cylinder and the cylinder head, between the piston rod and the cylinder head, between the piston and the piston rod and other parts are prone to leakage. When the vehicle is out of service for a long time and the hydraulic cylinder stops working for a long time, the static friction resistance of the seal ring is large and the wear is intensified. However, when the hydraulic cylinder has a lot of reciprocating times and the piston moves too fast, the wear of the seal ring will also increase. Both of these conditions will increase the leakage, Therefore, attention should be paid in practical work

leakage and sealing of hydraulic pipeline. The hydraulic pipeline of Dongfeng series dump truck adopts plane O-ring seal, which is mainly distributed between the high and low pressure pipe seat and the distribution valve, between the hydraulic cylinder and the oil inlet pipe seat, and between the oil inlet and outlet pipes of the oil pump. Pipeline leakage is mostly caused by loose bolts, damaged sealing rings, dust entering people, etc., which can be solved by tightening bolts, replacing sealing rings, cleaning mating surfaces, etc. In addition, a good working habit of regular inspection and maintenance should be formed. Once cracks are found in the oil pipe, it must be replaced immediately

abnormalities in the process of car lifting

according to the different abnormal conditions, the causes can be roughly divided into the following:

1 The gear pump operates but the carriage does not lift or the lifting is very slow. The most direct cause of this situation is insufficient oil pressure. The factors leading to insufficient oil pressure include: the valve rod of the distribution valve is not operated in place, the one-way valve in the valve is abnormal, there are foreign objects on the valve pad, the one-way valve is loose and falls off to block the pipeline, and other hydraulic pipelines are damaged, resulting in serious leakage and serious oil shortage. At this time, corresponding treatment methods should be taken according to different situations, such as replacing the gear pump, adjusting the gear of the distribution valve, overhauling, replacing the hydraulic cylinder Hydraulic pipeline, installation of check valve, etc. It is worth noting that when the gear position of the distribution valve is incorrect and the internal check valve is not tightly closed, the empty carriage may not stop in the middle

2. The carriage is difficult to lift and moves slowly. The reasons for the difficulty of lifting the carriage are as follows: insufficient fuel in the fuel tank; The oil tank filter or pipeline is seriously blocked; The oil pump is faulty and does not supply oil; The oil return valve of distribution valve is stuck in the oil return position; The overflow valve is seriously misadjusted and the high-pressure oil pump leaks; The lifting cylinder and limit valve are jammed, so that the air path to the distribution main valve is connected for a long time; Insufficient air pressure in the air reservoir; The power take-off and oil pump gear work poorly; The hydraulic oil is not clean, and impurities block the distribution valve

the reasons for the slow lifting and movement are as follows: the oil return circuit is not unblocked, and the friction resistance of the lifting cylinder is too large; The limit valve of lifting cylinder is not tightly closed, and the sealing ring of lifting cylinder is not tightly sealed, resulting in insufficient oil pressure; The working efficiency of the gear pump decreases, the oil volume of the oil tank is insufficient, and the gear pump cannot reach the specified oil discharge volume; The pipeline is seriously blocked or has leakage

3. The carriage cannot be lowered after lifting. There are several reasons for this situation: one is that the sliding rod of the distribution valve cannot be pulled in place; The piston rod is bent and deformed; Sometimes the motion pair of the lifting and tipping mechanism may stagnate due to debris pollution and long-term use; Improper operation, excessive lifting, and the angle exceeds the design maximum lifting angle, resulting in the dead center of the mechanism

4. The lifting angle of the carriage is insufficient or the lifting is unstable. There are generally no more than two situations in which this kind of fault occurs: one is that the oil is insufficient, and the other is that there is air in the oil. When the oil quantity is insufficient, the oil pressure cannot be reached, the carriage cannot be lifted to the maximum angle, and the lifting process is unstable

5. The carriage lifting cannot stop at any position or fall by itself after the carriage is lifted. The carriage lifting cannot be stopped at any position, which is mostly caused by the dirty oil, which makes the check valve not tightly sealed, or the distribution valve and oil return valve not tightly sealed; After the carriage is lifted, it falls down by itself. Reason: the check valve is stuck; The sealing ring of lifting cylinder is not well sealed; The distribution valve is stuck and not fully in place; There is leakage in the pipeline

troubleshooting of abnormal faults in the lifting process of heavy dump truck carriage

1 Check the oil level and oil leakage. First, check whether there is enough oil level. If not, add it as required. Check whether the power takeoff control mechanism works normally; Whether there is leakage in the oil and gas circuits, and if necessary, check whether they are blocked. Check whether the oil pump, distribution valve, limit valve, etc. work well, and whether the lifting cylinder is well sealed, and repair it if necessary. All kinds of control valves of the control system fail to operate and should be replaced with new parts. Replace the hydraulic oil when the hydraulic oil is not clean, causing oil blockage or insufficient hydraulic pressure, and the action is slow, and the carriage cannot be lifted in place. If the oil pump transmission mechanism or gear shaft sleeve is damaged, it cannot operate and the internal leakage is serious, it should be replaced and repaired

2. Maintenance of hydraulic transmission system. The wear of the journal and bearing of the driving and driven gears of the oil pump will increase the meshing clearance, reduce the displacement of the oil pump, reduce the working stability and generate noise. The wear, scratching and grooving of the gear end face and the end cover or end bearing of the pump body will cause the leakage of the oil inlet and outlet chamber inside the oil pump, which will increase the circuit. Therefore, the leakage from the oil outlet chamber through this circuit and the oil in the oil inlet chamber will increase, and the pressure and flow of the oil pump will decrease. Find the fault caused by the above abrasion damage, and replace it immediately after finding out the cause

3. Key points of hydraulic system maintenance. After the assembly is disassembled and disassembled, the parts should be carefully placed in the cleaning fluid to soak and clean, and avoid bumps and scratches. The cleaning of parts is very important. Dirt and metal impurities are strictly prohibited during assembly, so as not to aggravate the wear, stagnation and failure of parts. Select and add enough working oil in strict accordance with the regulations, filter it if necessary, and ensure that the oil is clean; The system should be free of leakage during use. During maintenance, avoid knocking of parts to prevent damage and deformation of parts

sealing and leakage treatment of hydraulic system of heavy dump truck

sealing and leakage treatment of oil pump, distribution valve, hydraulic cylinder and pipeline of heavy dump truck are as follows:

1 Seal at oil pump journal. Two self tightening oil seals are installed at the Journal of the oil pump of common heavy dump trucks, and the outer end is blocked by the hole with a retaining ring. Its function is to prevent oil leakage in the oil pump and prevent the entry of external air and dust. Once oil leakage is found here, the self tightening oil seal should be replaced immediately. During installation, be sure not to scratch the oil seal with the spline shaft. In addition, the oil seal will deteriorate if the speed is too high and the local temperature rises too fast

2. Seal between oil pump and transition plate. In the structure of using the pump and valve as a whole, the oil pump and the transition plate are sealed with a ○ shaped sealing ring. Because this part is fixed with hexagon bolts, sometimes the fastening bolts are loose due to uneven stress, which will cause oil leakage at this part. Therefore, pay attention to tightening the fastening bolts during vehicle maintenance

3. Hazards of oil pump oil leakage. Oil leakage of the oil pump will cause increased oil pump noise, insufficient or no pressure of the hydraulic system, insufficient or no displacement of the oil pump and excessive temperature. Therefore, in case of abnormal operation of the oil pump, it is necessary to

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