Created on:2021-12-07 13:32

Fault analysis and troubleshooting of vane pump

Fault analysis and troubleshooting of vane pump

When the vane pump is working, the anti oil pollution ability is poor, and the matching accuracy between the vane and the rotor slot is also high, so there are many faults. The causes of common faults of the vane pump and the troubleshooting methods are as follows.

1. High noise of vane pump

(1) Cause analysis.

1) The inner surface of the stator is roughened.

2) The transition surface of stator in oil absorption area is slightly worn.

3) The blade top is not perpendicular to the side or the top chamfer is too small.

4) The triangular groove on the oil pressure window of the oil distribution plate is blocked or too short or shallow, causing oil trapping.

5) The pump shaft is different from the motor shaft.

6) Work under rated pressure.

7) The oil suction port is not tightly sealed and air enters.

8) Cavitation occurs.

(2) Exclusion method.

1) Polish the inner surface of the stator.

2) Turn the stator around the radius and install it.

3) Grind the blade top to ensure that its perpendicularity is within 0.01mm; Chamfer the blade top to 1 × 45 ° (or ground into arc shape) to reduce the sudden change of compressive stress.

4) Clean (or trim) the triangular groove with a shaping file to eliminate oil trapping.

5) Adjust the coupling so that the coaxiality is less than Φ 0.01mm。

6) Check the working pressure and adjust the overflow valve.

7) Check with grease coating method, remove the oil suction pipe joint, clean it, apply sealant, install and tighten it.

8) Check the oil suction pipe, oil tank, filter, oil level and oil viscosity to eliminate cavitation.

2. The vane pump has low guest volume efficiency and low pressure rise

(1) Cause analysis.

1) The movement of individual blades in the rotor slot is not live or even stuck.

2) The blades are installed reversely.

3) Poor contact between the inner surface of the stator and the top of the blade.

4) The fit clearance between blade and rotor blade groove is too large.

5) The end face of the oil distribution plate is worn.

6) The oil viscosity is too high or too low.

7) The rotating speed of the motor is too low, and the centrifugal force cannot throw the blade out of the rotor slot, forming an unchangeable sealing space.

8) The oil suction port is not tightly sealed and air enters.

9) Cavitation occurs.

(2) Exclusion method.

1) Check the fit clearance (generally 0.01 ~ 0.02mm). If the fit clearance is too small, it shall be matched with a single groove.

2) Correct the assembly direction.

3) Grind the working surface (or replace the oil distribution plate).

4) The blade shall be equipped with a single blade according to the rotor blade slot to ensure the fit clearance.

5) Grind the end face of the oil distribution plate (or replace the oil distribution plate).

6) Measure the oil viscosity and select the oil according to the instructions.

7) Check the speed and eliminate the root cause of the problem. Generally, when the rotating speed of vane pump is lower than 500r / min, oil cannot be sucked. However, when the rotating speed is higher than 1500r / min, the oil can not be sucked.

8) Check with grease coating method, remove the oil suction pipe joint, clean it, apply sealant, install and tighten it.

9) Check the oil suction pipe, oil tank, filter, oil level and oil viscosity to eliminate cavitation.

3. High oil temperature and abnormal heating

(1) Cause analysis.

1) Due to incorrect assembly dimension chain, the clearance of sliding fit is too small, resulting in surface roughening or inflexible rotation, resulting in excessive friction resistance and large rotating torque during operation.

2) The clearance of each sliding mating surface is too large, or the internal leakage after wear is too large, and the pressure and flow loss become heat energy.

3) The motor shaft and pump shaft are not installed concentrically and generate heat.

4) The pump works for a long time under the condition that the pressure is close to or exceeds the rated pressure, or the temperature rises due to heating due to the failure of the pressure control valve.

5) The oil return pipe of the oil tank is too close to the oil suction pipe, and the oil return is too late to cool, and it is immediately sucked into the pump, resulting in an increase in temperature.

6) The oil volume of the oil tank is insufficient, or the design capacity of the oil tank is too small, or the cooling water volume of the cooler is insufficient.

7) The ambient temperature is too high.

(2) Exclusion method.

1) When the assembly dimension chain is incorrect, it can be disassembled, deburred and polished again, and the fit clearance can be guaranteed for reassembly. If the relevant parts are seriously worn, they must be replaced.

2) Check whether the clearance of each sliding mating surface meets the requirements. If the internal leakage is too large due to wear, repair or replace the corresponding parts in time.

3) Check and correct the installation concentricity of motor shaft and pump shaft.

4) Avoid the pump working near or exceeding the rated pressure for a long time. If the pressure control valve is faulty, it shall be checked and eliminated in time.

5) Check and adjust the position of oil return pipe and oil suction pipe of oil tank.

6) Check and add hydraulic oil to the specified position, or replace the redesigned large capacity oil tank, check the cooling water volume of the cooler and add cooling water as required.

7) Shorten the working time in high temperature environment.

4. Large pressure fluctuation

(1) Cause analysis.

1) The reason for high noise is often high pressure fluctuation. Refer to the high noise of vane pump to find out the reason.

2) The pressure regulating spring of pressure limiting variable vane pump is bent, deformed or too soft.

3) Abnormal other valves (such as overflow valve) can cause pressure fluctuation.

(2) Exclusion method.

1) Refer to the treatment method of large noise of vane pump.

2) Timely check whether the pressure regulating spring of pressure limiting type is bent, deformed or too soft, and timely replace the qualified spring if necessary.

3) Check other valves for abnormal operation and good performance, and solve problems in time.

5. Leakage

(1) Cause analysis.

1) Leakage from oil seal (pump shaft). If the oil seal is not installed properly, such as the clamping spring at the sealing lip falls off, it is scratched by the shaft head burr during installation, leakage is caused by dirt pulling or pump shaft wear during use, or the oil at the oil seal is blocked due to leakage, and the pressure suddenly rises, breaking through the oil seal (belonging to low-pressure seal ring).

2) Oil leakage of pump body and pump cover connecting table.

3) Leakage at the joint surface of left and right pump bodies.

(2) Exclusion method.

1) First, check whether the oil seal is installed properly. During assembly, pay attention not only to the processing and assembly quality of the oil seal (such as the concentricity control of the connection between the pump shaft and the motor), but also to dredge the oil drain channel at the oil seal to avoid the oil seal breaking due to the increase of pressure when oil is trapped here. An oil seal with a sealing pressure of about 20MPa can be selected as appropriate.

It is worth mentioning that the installation direction of the pump shaft oil seal of Yb vane pump is actually wrong, and the installation direction of the pump shaft oil seal of YB1 vane pump is improved. One of the bearings is used to prevent external leakage of oil, and one of the shaft heads is used to prevent the oil pump from sucking air. In other words, oil leakage and air intake at the pump shaft oil seal of Yb vane pump are inevitable and must be corrected.

2) The right pump body and pump cover of Yb vane pump are sealed by paper gasket, which is easy to leak. However, the O-ring is changed between the right pump body and pump cover of YB1 vane pump, which significantly improves the reliability of the seal.

3) Check the groove quality of the corresponding O-ring seal and the damage of the O-ring seal for symptomatic treatment. In addition, check the tightening of the compression screw.

6. The vane pump is seriously worn and burnt out in a short time

(1) Cause analysis.

1) The inner surface of stator and blade head are seriously worn.

2) The rotor is broken. Rotor fracture often occurs at the root of oil pump blade groove. The causes of fracture are as follows: the rotor adopts 40Cr material, which has good hardenability. During quenching, the surface and center of the rotor are hardened, and it is easy to fracture under impact load; The stress on the dangerous section between the small holes at the blade root is large, and the stress concentration is often caused by poor processing. In particular, some manufacturers adopt the process of milling the blade groove first and then drilling the round hole at the root of the blade groove, which is even worse; In addition, foreign matters are sucked into the pump and the rotor is broken. Sometimes, the pressure ring at the end of the needle bearing at the left end of the pump shaft (Yb vane pump) is disengaged, and the bearing needle is often sucked into the pump, resulting in the fracture of the rotor.

3) The operation condition of vane pump is poor. If the vane pump works under the conditions of overload, high temperature corrosive gas, oil leakage and water leakage, oxidation and deterioration of hydraulic oil for a long time, abnormal wear and cavitation wear are easy to occur.

4) Poor assembly of vane pump after disassembly and repair. If the axial thickness difference between the rotor and the pump body is too small, forcibly assemble the compression screw, and install it on the main engine when the pump cannot rotate flexibly by hand, and the vane pump will be burned in a short time.

5) The pump shaft is broken. Dirt enters the pump and is clamped between the rotor and stator, rotor and oil distribution plate and other relative moving sliding surfaces, so that the pump shaft is broken due to excessive torque transmission. Therefore, dirt shall be strictly prevented from entering the pump; The pump shaft is broken due to the wrong material selection and poor heat treatment; Other valve components in the system, such as the overflow valve, fail to operate, and the system generates abnormal high pressure. If there are no other safety protection measures, the pump will overload and break the shaft.

(2) Exclusion method.

1) If the inner surface of stator and blade head are seriously worn. At this time, if the oil pump is carefully disassembled and the blade is taken out, filaments can be seen sticking to the blade head of wl8cr4v material under strong light. At this time, it can be changed to 38crmoaia and nitrided to hv900, which greatly improves the wear of stator and blade.

2) If the rotor breaks. At this time, the following measures can be taken: changing the rotor material from 40Cr quenching hrc52 to 20Cr carburizing quenching can greatly improve the impact toughness of the rotor, and generally there will be no fracture. Appropriately reduce the diameter of the small holes at the blade root and appropriately enlarge the distribution circle diameter of the small holes at the blade groove root, so as to increase the strength of the dangerous section; Adhere to the process of drilling the small hole at the blade root first and then milling the blade groove to avoid stress concentration; Prevent foreign matters from being sucked into the pump; Change needle roller bearing to ball bearing (YB1 vane pump).

3) The operation condition of vane pump is poor. At this time, only by changing the working conditions of the vane pump can it work.

4) When assembling the vane pump after disassembly and repair, refer to the working principle and structural diagram of the vane pump, grasp the dimensional gap between each other, carefully clean, carefully assemble and rotate flexibly before installing it into the main engine.

5) When the pump shaft is broken, it shall be carefully checked and targeted measures shall be taken.

7. Loose bearing and shaft seal

(1) During installation, the output shaft of the vane pump is not concentric with the output shaft of the motor (the output shaft of the motor is deformed, the coupling is not concentric, the stop positioning clearance of the vane pump is too large, the installation fixing screw is not tightened, etc.) or butts against each other, and the bearing and shaft seal are damaged due to too large radial force or runout (irregular operation) during the operation of the vane pump, If not handled in time, the pump core components will be worn and scrapped.

(2) The motor bearing has been worn. This phenomenon cannot be judged when the vane pump has no load. It is normal when the vane pump has no load. During operation, the motor output shaft swings due to clearance, which drives the vane pump output shaft to swing and damages the bearing and shaft seal.

(3) Improper assembly, because the vane pump runs at high speed during operation, it is easy to cause damage if it is improperly assembled (not installed in place or the shaft package is biased).

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