Hydraulic Pump as a power component in the hydraulic system, to the whole hydraulic system to provide high pressure hydraulic oil, to drive other hydraulic components to complete the expected action requirements, is the power source of hydraulic system. When the hydraulic system problems, the first to think of the hydraulic pump. Through the analysis of various hydraulic pump failures, listed the common failures and causes, and finally find out the solution.
Although there are many types of hydraulic pumps, the working principle and function of hydraulic pumps are the same, so the hydraulic pump can be studied as a separate object. After the investigation and analysis of the faults that often occur in the work of various hydraulic pumps, the common faults that often occur in hydraulic pumps are summarized as follows:
1.1 No oil or no pressure is absorbed by hydraulic pump
Hydraulic pump suction oil or no pressure, the whole hydraulic system will not work, affecting the efficiency of the system. The reasons are: 1. The prime mover and OIL PUMP rotation is inconsistent; 2. Oil Pump transmission key falls off; 3. Oil inlet and outlet are reversed; 4. The oil level in the tank is too low, and the suction pipe mouth is exposed; 5. The speed is too low and the suction is insufficient; 6 oil viscosity is too high, so that the blade movement is not flexible; 7. The oil temperature is too low, so that the oil viscosity is too high; 8. Blockage of suction pipe or filter device causes poor oil absorption; 9. High filtering accuracy of suction inlet filter causes poor oil absorption; 10. Low filtration accuracy of the system oil leads to the blade getting stuck in the groove; 11. Insufficient suction of small displacement oil pump; 12. Air leakage in suction pipe.
Corresponding solutions: 1. Correct the turning direction of the prime mover; 2. Reinstall the transmission key. 3. Select the correct connection according to the instructions; 4. Fill the oil to the lowest oil mark; 5. Increase the speed to above the minimum speed of the oil pump; 6. Choose working oil with recommended viscosity; 7. Heat to recommended normal working oil temperature; 8. Clean the pipeline or filter device, remove the blockage, replace or filter the oil in the tank; 9. Select the filter correctly according to the instructions; 10. Disassemble, repair and grind the internal parts of the oil pump, reinstall them carefully, and replace the oil; 11. Fill the pump with oil; 12. Check the joints of the pipeline and seal them firmly.
1.2 The flow rate of hydraulic pump is not up to the rating
When the hydraulic pump flow is insufficient, the speed and pressure of the actuator are unstable, and the external work can not be achieved. The common reasons are: 1. The speed does not reach the rated speed; 2. There is leakage in the system; 3. Because the oil pump works for a long time and vibrates, the screw of the pump cover loosens; 4. Leakage of suction pipe; 5. The oil level in the tank is too low; 6. The inlet oil filter is blocked or the flow is over; 7. The suction pipe is blocked or the diameter is small; 8. Oil viscosity is too high or too low; 9 variable pump flow regulation is improper.
The corresponding solutions: 1. Choose the motor speed according to the rated speed specified in the manual; 2. Check the system and repair the leakage point; 3. Tighten the screws properly. 4. Check the joints and seal and tighten them; 5. Fill the oil to the lowest oil mark; 6. Clean the filter or choose an oil filter with a flow rate more than 2 times that of the oil pump; 7. Clean the pipe, choose suction pipe not less than the inlet diameter of the oil pump; 8. Use recommended viscosity working oil; 9. Adjust to the required flow rate.
1.3 The pressure of the hydraulic pump cannot rise
The common reasons are: 1. The oil pump is not filled with oil or the flow is insufficient; 2. The adjustment pressure of the relief valve is too low or faulty; 3. There is leakage in the system; 4. Because the oil pump vibrates for a long time, the screw of the pump cover loosens; 5. Leakage of suction pipe; 6. Insufficient oil absorption; 7. Variable pump pressure adjustment is improper.
Corresponding solutions: 1. Same as the above-mentioned exclusion method; 2. Adjust the relief valve pressure or repair the relief valve; 3. Check the system and repair the leakage point; 4. Tighten the screws properly. 5. Check the joints and seal and tighten them; 6. Same exclusion method as above; 7. Adjust to desired pressure.
1.4 Serious noise and pressure fluctuation
Serious noise and pressure fluctuation have a great impact on the performance and working environment of the hydraulic system. The reasons are: 1. Suction tubing or oil filter is partially blocked; 2. The oil suction end connection is not tightly sealed, air enters, and the oil suction position is too high; 3. Air enters from the oil seal of the pump shaft; 4. The screw on the pump cover is loose. 5. The pump and the shaft connecting device are different or loose; 6. The oil viscosity is too high, and there are bubbles in the oil; 7. The passing capacity of suction oil filter is too small; 8. The rotational speed is too high; 9. Pump body cavity obstruction; 10 Gear Pump tooth shape precision is not high or poor contact, pump parts damaged; 11. The axial clearance of the gear pump is too small, and the vertical degree of the inner hole and the end face of the gear or the parallelism of the two holes on the pump cover is blocked. 12. Pipeline vibration.
The corresponding solution is: 1. Remove dirt, make suction pipe smooth; 2. Oil at the oil sucking end connection, if there is better, tighten the connector, or replace the seal, reduce the oil sucking height; 3. Replace the seal. 4. Tighten properly; 5. Reinstall it to make it concentric and tighten the connector; 6. Change the hydraulic oil with appropriate viscosity to improve the quality of oil; 7. Use oil filters with larger passing capacity; 8. Make the speed of rotation lower than the maximum allowable speed; 9. Clean or replace the pump body; 10. Replace gear or grind dressing, replace damaged parts; 11. Check and repair related parts disassembly relief valve cleaning; 12. Take isolation and vibration mitigation measures.
1.5 Overheating
The main reasons for the failure of hydraulic pump overheating are as follows: 1. Oil viscosity is too high or too low; 2. 2. Serious friction between side plate and shaft sleeve and gear end face; 3. Poor cleanliness of oil, aggravated internal wear, so that the volume efficiency decreases, oil leakage from the internal clearance throttling and generate heat; 4. Too small tank volume, poor heat dissipation; 5 system overload, mainly in the pressure or speed is too high;
The corresponding solution is: 1. Replace with a suitable viscosity of hydraulic oil; 2. Repair or replace the side plate and shaft sleeve; 4. Increase the fuel tank to expand the heat dissipation area; 5. Adjust the pressure and speed.
1.6 Leakage
The leakage of the hydraulic pump directly determines the output flow of the hydraulic pump, which will affect the stability of the hydraulic system speed and the output power. The main reasons for the failure: 1. The center spring of the plunger pump is damaged, so that the cylinder block and the oil distribution cross lose the sealing; 2. Oil seal or sealing ring damage; 3. Poor sealing surface; 4 pump parts wear, clearance is too large.
The corresponding solution is: 1. Replace the spring; 2. Replace the oil seal or sealing ring; 3. Check and repair; 4. Replace or rematch the parts.
1.7 Inspection and repair of hydraulic pump bearings
1. Service life of bearings
The most important part of the plunger pump is the bearing. If the bearing clearance is out of whack during use, the normal clearance between the piston rod and the cylinder body hole, the slipper and the swash plate, the valve plate and the cylinder body distribution surface cannot be guaranteed. At the same time, the hydrostatic oil film thickness of the friction pair will be destroyed, and the service life of the piston pump bearing will be reduced. In the process of use, bearings should be regularly repaired and replaced according to the provisions of the manual. According to the manufacturer's data, the average service life of the bearing is about 10h, if it exceeds this value, a new bearing needs to be replaced.
2. Bearing detection
Bearing detection items are mainly bearing clearance, bearing clearance detection to use professional testing instruments, therefore, in the maintenance process, can only use the visual method for simple inspection, such as the roller surface of the bearing is found to have scratches or discoloration, the bearing must be replaced.
3. Precautions when replacing bearings
When replacing bearings, attention should be paid to the English letter of the original bearing (representing the accuracy grade) and the model. Bearings used on the plunger pump mostly use large load capacity bearings. It is best to buy the original manufacturer and the original specification products when replacing the bearings. If you can not buy, need to replace, should look up the table replacement, the purpose is to maintain the accuracy of bearing grade and load capacity, otherwise it will affect the use of the pump effect, serious will reduce the service life of the pump.
