1. Failure phenomenon and cause analysis When troubleshooting, the following three factors are used to find the cause of the failure and improve the system:
(1) Check the inside leakage of the boom cylinder. The easiest way is to raise the boom to see if there is a clear and free fall. If the drop is obvious, check the cylinder for disassembly and replace the seal if worn.
(2) Check the valve. First, clean the safety valve and check if the spool is worn out. Replace it if worn. After the installation of the safety valve, if there is still no change, check the condition of the valve core of the pilot valve. The clearance limit is 0.06mm, and the wear should be replaced.
(3) Measure the pressure of the hydraulic pump. If the pressure is low, then adjust, and the pressure can not be adjusted, then the hydraulic pump is seriously worn.
In general, the main reason that causes the boom load to fail to increase is:
a. Hydraulic pump seriously worn. When the pump is running at low speed, the leakage in the pump is serious. At high speed, the pump pressure slightly increases. However, due to the wear and internal leakage of the pump, the volumetric efficiency drops significantly and it is difficult to reach the rated pressure. The long time working of the hydraulic pump exacerbates the wear and causes the oil temperature to rise, which causes the wear of the hydraulic components, the aging and damage of the seal, the loss of the sealing ability, the deterioration of the hydraulic oil, and eventually the failure.
b. The selection of hydraulic components is unreasonable. The boom cylinder specifications are 70/40 non-standard series, and the seals are also non-standard parts. The manufacturing cost is high and the seal replacement is inconvenient. Boom cylinder bore is small, it is bound to set the system high pressure.
c. The hydraulic system design is unreasonable. The control valve and the hydraulic steering gear are connected in series with a single pump. The safety valve set pressure is 16 MPa, and the rated working pressure of the hydraulic pump is also 16 MPa. Hydraulic pumps are often operated under full load or long-term overload (high pressure) conditions, and the system has hydraulic impact, long-term oil change, hydraulic oil contamination, exacerbated hydraulic pump wear, resulting in hydraulic pump casing burst (later discovered Such failures).
2. Improvements and Effects (l) Improve the design of hydraulic systems. After many arguments, the advanced priority valve and the load-sensing full hydraulic steering gear were used in the final form, as shown in Figure 2. The new system can prioritize the distribution of traffic according to the steering requirements, ensuring that the fuel supply is adequate regardless of the size of the load and the steering wheel speed, and the remaining part can be supplied to the working device circuit to eliminate the power caused by excessive oil supply to the steering circuit. The loss increases the system efficiency and reduces the working pressure of the hydraulic pump.
(2) Optimize the design of boom cylinders and hydraulic pumps to reduce system operating pressure. With optimized calculations, the boom cylinder uses the standard series 80/4. The displacement of the hydraulic pump was increased from 10 ml/r to 14 ml/r, and the system set pressure was 14 MPa, which satisfied the lifting force and speed requirements of the boom cylinder.
(3) In the process of use, attention should also be paid to the correct use and maintenance of the loader, adding or replacing hydraulic oil on a regular basis, maintaining the cleanliness of hydraulic oil, and strengthening daily inspection and maintenance.
(1) Check the inside leakage of the boom cylinder. The easiest way is to raise the boom to see if there is a clear and free fall. If the drop is obvious, check the cylinder for disassembly and replace the seal if worn.
(2) Check the valve. First, clean the safety valve and check if the spool is worn out. Replace it if worn. After the installation of the safety valve, if there is still no change, check the condition of the valve core of the pilot valve. The clearance limit is 0.06mm, and the wear should be replaced.
(3) Measure the pressure of the hydraulic pump. If the pressure is low, then adjust, and the pressure can not be adjusted, then the hydraulic pump is seriously worn.
In general, the main reason that causes the boom load to fail to increase is:
a. Hydraulic pump seriously worn. When the pump is running at low speed, the leakage in the pump is serious. At high speed, the pump pressure slightly increases. However, due to the wear and internal leakage of the pump, the volumetric efficiency drops significantly and it is difficult to reach the rated pressure. The long time working of the hydraulic pump exacerbates the wear and causes the oil temperature to rise, which causes the wear of the hydraulic components, the aging and damage of the seal, the loss of the sealing ability, the deterioration of the hydraulic oil, and eventually the failure.
b. The selection of hydraulic components is unreasonable. The boom cylinder specifications are 70/40 non-standard series, and the seals are also non-standard parts. The manufacturing cost is high and the seal replacement is inconvenient. Boom cylinder bore is small, it is bound to set the system high pressure.
c. The hydraulic system design is unreasonable. The control valve and the hydraulic steering gear are connected in series with a single pump. The safety valve set pressure is 16 MPa, and the rated working pressure of the hydraulic pump is also 16 MPa. Hydraulic pumps are often operated under full load or long-term overload (high pressure) conditions, and the system has hydraulic impact, long-term oil change, hydraulic oil contamination, exacerbated hydraulic pump wear, resulting in hydraulic pump casing burst (later discovered Such failures).
2. Improvements and Effects (l) Improve the design of hydraulic systems. After many arguments, the advanced priority valve and the load-sensing full hydraulic steering gear were used in the final form, as shown in Figure 2. The new system can prioritize the distribution of traffic according to the steering requirements, ensuring that the fuel supply is adequate regardless of the size of the load and the steering wheel speed, and the remaining part can be supplied to the working device circuit to eliminate the power caused by excessive oil supply to the steering circuit. The loss increases the system efficiency and reduces the working pressure of the hydraulic pump.
(2) Optimize the design of boom cylinders and hydraulic pumps to reduce system operating pressure. With optimized calculations, the boom cylinder uses the standard series 80/4. The displacement of the hydraulic pump was increased from 10 ml/r to 14 ml/r, and the system set pressure was 14 MPa, which satisfied the lifting force and speed requirements of the boom cylinder.
(3) In the process of use, attention should also be paid to the correct use and maintenance of the loader, adding or replacing hydraulic oil on a regular basis, maintaining the cleanliness of hydraulic oil, and strengthening daily inspection and maintenance.
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