Created on:2021-09-24 14:44

Construction and construction machinery_ Use and maintenance of hydraulic system of concrete mixer

Construction and construction machinery_ Use and maintenance of hydraulic system of concrete mixer

The correct installation, use, maintenance and maintenance of hydraulic components are as important as the selection of appropriate hydraulic components. Reasonable installation, use and timely maintenance can not only give full play to the best performance of hydraulic components, but also greatly prolong the service life of hydraulic components.

① Inspection and commissioning before installation and use

a. Before installation, check whether the components are intact. Before injecting hydraulic oil, ensure that all system components (oil tank, rubber hose, connector and other accessories) are clean.

b. During refueling, the hydraulic oil shall be filtered by an oil filter with a filtering accuracy of no less than 10. The use of waste oil is absolutely prohibited. The 46# high-quality anti-wear hydraulic oil shall be used to optimize the performance of hydraulic components. Select 32# anti-wear hydraulic oil in high cold area and 68# anti-wear hydraulic oil in high temperature area.

c. Before starting the system, ensure that the pump, motor housing and oil suction hose connected to the oil tank are filled with qualified oil; Check all pipeline joints to ensure that there is sufficient preload and there is no clamping or air leakage. After the system is installed, each pressure gauge can be installed to measure the oil make-up pressure, system pressure and vacuum degree. The vacuum gauge can also be installed on the oil suction pipeline near the filter element to directly observe the vacuum degree.

d. When starting the system, ensure that the pump control handle is in the middle position, start the engine, run at idle speed with no load, replenish oil to the oil tank in time, and observe the oil replenishment pressure gauge until the oil replenishment pressure of 1.2 ~ 1.5MPa is established. Run for 3 ~ 5 min under this state, increase the engine speed to normal, and the oil make-up pressure shall remain stable (if the oil make-up pressure is insufficient, shut down the engine in time and check the cause to avoid damaging the hydraulic components).

e. Make sure that the pump control handle is in the middle position, make the engine work at the speed of 1500-1600r / min, and then slowly pull the pump control handle to rotate the mixing drum clockwise or counterclockwise. If there is no abnormality after running for 5min, it indicates that the system is in good condition.

f. Remove the pressure gauge for detection, install the plug and check the oil level. If the oil level is low, supplement the hydraulic oil.

After debugging, the system can be put into use.

② Daily use, maintenance and servicing

a. During the use of the vehicle, it is necessary to regularly check whether the pipeline connections of the system are loose or oil leakage. If there is any loose or oil leakage, it shall be handled in time.

b. The filter element shall be replaced under the following circumstances: after the new vehicle is put into use, the hydraulic oil shall be replaced for the second time and each time in the future; During operation, the vacuum gauge shall be observed frequently. When the hydraulic oil temperature of the system is higher than 50 ℃, if the oil suction vacuum gauge of the make-up oil pump shows an absolute pressure lower than 0.075mpa (0.75bar) or an absolute pressure lower than 0.05Mpa (0.5bar) during cold start, the filter element shall be replaced in time, so as to avoid the difficulty of oil suction of the make-up oil pump or the increase of oil return resistance and damage to the hydraulic components.

c. Replace the hydraulic oil under the following conditions; Put into use for the first time to 100h after use; Replace the hydraulic oil for the first time until 500h after replacement; Thereafter, the replacement cycle is every 1000h. If the equipped oil tank is a vent oil tank, the replacement cycle shall be 500h. If the hydraulic oil is emulsified after mixing with water or the hydraulic oil has deterioration odor due to high oil temperature, it shall be replaced immediately. The replaced hydraulic oil shall use high-quality 46# anti-wear hydraulic oil, 32# anti-wear hydraulic oil shall be selected in alpine areas, and 68# anti-wear hydraulic oil shall be selected in high-temperature areas. No matter which brand of hydraulic oil is replaced, the same brand must be used. Do not inject other oil products for mixed use. In addition, the oil level of the oil tank shall be checked frequently. If the hydraulic oil is missing, it shall be supplemented in time. When replacing the hydraulic oil, pay attention to drain the oil when the hydraulic oil is hot just after the mixer is completed, so as to easily bring out mechanical impurities and oil stains.

d. If the filter element is installed above the oil tank, regularly check whether the oil suction pipe is loose or leaking. It is forbidden to start the engine or work when the oil suction pipe is loose or falls off, otherwise the hydraulic pump will be damaged or scrapped.

e. When the mixer is in use, it is not suitable to stop at will or start frequently; During unloading, properly control the unloading speed and discharge evenly according to the pumping situation or actual use situation, so as to avoid repeated unloading as soon as possible. In this way, not only the power consumption is large, but also the hydraulic pump and motor are in pressure alternation, which is easy to be damaged. When operating the control handle of the hydraulic pump, the action shall be soft and do not push or pull.

f. During use in winter, due to low ambient temperature and high viscosity of hydraulic oil, the pipeline oil flow resistance and oil suction resistance of hydraulic pump increase. In addition to selecting appropriate hydraulic oil, special attention shall be paid to avoid empty suction or seal damage of hydraulic pump during operation (ensure that the displacement control handle of pump is placed in the middle before starting the engine each time; After startup, it shall run at low speed for 10min (and then load and run).

③ Common troubleshooting of hydraulic system most of the reasons for faults in the hydraulic system are that the hydraulic oil is polluted and can not be handled in time, but there will also be quality problems of hydraulic components themselves. Common faults and troubleshooting are as follows.

a. The mixing drum jumps on the supporting roller. The main reason for this is that the rotating speed of the mixing drum fluctuates suddenly over a period of time. The reasons for the sudden fluctuation and change of the rotating speed of the mixing drum are as follows: first, improper operation makes the engine throttle unstable, which can not be eliminated through the transmission of the hydraulic system. This situation can be solved only by correct operation; Second, there are abnormal conditions at the oil distribution plate in the hydraulic pump, so that the oil distribution and leakage occur alternately, resulting in fluctuations in the output speed of the hydraulic motor. You can connect the oil make-up pressure gauge for inspection. You will find that the oil make-up pressure fluctuates when the mixing drum jumps during operation. At this time, it is generally necessary to disassemble the pump body in a clean environment for inspection, Replace the oil distribution plate or replace the oil distribution plate together with the lining plate.

b. When the load increases, the rotating speed of the mixing drum decreases. Connect the make-up pressure gauge and observe the change of make-up pressure when the load increases. If the oil make-up pressure decreases, the rotating speed of the mixing drum will decrease. In this case, the hydraulic system is generally used for a long time. During the use of the vehicle, the hydraulic oil and filter element are not replaced in time, resulting in the wear of moving elements in the pump and Mada, such as oil distribution plate, lining plate, plunger and cylinder block, the decline of volumetric efficiency and the difficulty of establishing high pressure. The solution is to replace the oil distribution plate and lining plate. For the wear of the plunger and cylinder block, the plunger can be treated by electroplating, grinding and other process methods, or directly find a professional maintenance factory [meikomas] to repair or replace the pump and motor.

c. The mixing drum rotates normally in one direction and abnormally in the other direction. It may be that the shuttle valve is "stuck" at a certain position, which can be solved by overhauling the shuttle valve in the integrated valve block on the hydraulic motor; It may also be the fault of the high-pressure relief valve rotating in an abnormal direction. Check the two high-pressure relief valves in the integrated valve block. If the fault direction changes, it is proved to be the fault of the high-pressure relief valve, which can be replaced.

D. foam in the hydraulic tank, and the hydraulic oil is discharged from the gas vent of the oil tank. In this case, air enters the system, and the air must enter the system from the negative pressure. Analyze each rubber hose and interface of the system, and only the oil suction pipe and interface are in negative pressure state. First observe the reading of the vacuum gauge. If it is within the normal range, replace the oil suction hose; If the reading of the vacuum gauge is out of range, replace the oil suction filter element.

e. First aid measures for failure vehicle filled with concrete. If the hydraulic system of a mixer truck filled with concrete breaks down suddenly, the mixing drum cannot operate and the concrete cannot be unloaded. According to the basic judgment of this kind of hydraulic system failure, the failure probability of hydraulic pump is higher than that of hydraulic motor. In order to prevent the concrete from solidifying in the mixing drum, another normal mixing truck matched with the system can be driven near the fault truck, and three lengthened rubber hoses (two high-pressure rubber hoses and one pump motor connecting rubber hose) can be used to connect the hydraulic motor of the fault truck with the hydraulic pump of the normal truck to form a new transmission system, The hydraulic motor of the failed truck is driven by the hydraulic pump of the normal truck to discharge the concrete in the mixing drum of the failed truck. Then repair the faulty vehicle. After each repair, the hydraulic oil and filter element shall be replaced and maintained on time according to the use method of the new vehicle.

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