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Correct use and failure judgment of vane pump

Correct use and failure judgment of vane pump

There are generally detailed installation guidelines and precautions in the product manual of the vane pump, but in actual use,

It is often not valued by people, and improper use will always cause the failure of the vane pump. According to the United States hydraulic industry

Statistical analysis shows that most of the failures of vane pumps are caused by improper use, and improper use accounts for the proportion of oil pump damage.

The cases are as high as 95%, so we have the responsibility to promote the correct use of vane pumps to the majority of vane pump users.

As we all know, in the hydraulic system, the component that is most prone to failure is the oil pump, and the failure ratio of the hydraulic valve and the cylinder is relatively

Oil pumps are much less, they can be solved by cleaning at most, and once the vane pump fails, it is fatal. For this reason,

Whether the vane pump can be used correctly is very important. In order to distinguish which type of problem it belongs to, use it correctly and determine the cause of the failure.

Provide the following experience for reference:

1. Several manifestations of improper use:

1. Incorrect installation of the coupling: As the clearance between the coupling and the shaft is too small or there is no gap, the bearing will be injured when it is struck hard.

Cause early damage to the bearing and affect the life of the entire pump core. Furthermore, if the coupling is installed without a certain axial clearance,

If the pump is directly and rigidly mounted on the pump sleeve with screws, the bearing will be stressed in the axial direction. If the bearing is subjected to axial force for a long time, the bearing will be

It quickly damaged and produced eccentricity and affected the pump core. On the surface, it seemed that the pump core was malfunctioning, but the bearing was actually stressed.

(This is the number one killer of oil pump damage)

2. Coaxiality is out of tolerance: If the coaxiality exceeds the specified value during installation, the bearing and the entire pump core will be eccentric and early damage.

It will also be cut off (the shaft is cut at the thickest part of the shaft head), and the coaxiality is generally controlled at ≤0.1mm.

3. The oil is too dirty: Because the oil tank is not sealed, the surrounding dust and debris are mixed into the oil, causing the cleanliness of the oil to exceed

Standard, if the filter accuracy is insufficient or there is no filter, the pump core will be scratched and damaged quickly, especially the hydraulic oil tank of the new equipment.

The welding slag left in the pipeline or the tank cleaning is not clean will cause the new pump to start the research pump accident.

(This is the second biggest killer of oil pump damage)

4. Oil deterioration: due to the use of expired hydraulic oil or regenerated oil, the surface of the pump core parts is black or viscous.

The sundries, poisons and corrosiveness in the oil can cause early damage to the oil pump, and the regenerated expired oil will also cause the pump due to lack of lubrication and anti-wear properties.

The core life is greatly shortened, even the blades and the pump core can not move.

The service life of anti-wear hydraulic oil is 2000-3000 hours (continuous half a year) according to the introduction of the oil company. It can be extended when the environment is better.

Long life to 6000 hours (approximately one year), therefore, it is recommended that customers replace the new oil once a year.

(This is the third biggest killer of oil pump damage)

5. The oil temperature is too high: As the cooling device is not installed, the oil temperature will continue to rise during continuous use of the machine. If the oil temperature is long

When the temperature is above 70°C, the life of the oil pump will be greatly shortened, and it will be damaged in half a year to a year.

6. Water in the oil: In a device with water cooling, due to the poor sealing of the "water cooling device", water enters the oil.

The liquid will appear milky white (emulsification), the internal metal parts of the oil pump will rust or partially rust, and the pump will accelerate the wear during high-speed rotation.

Damage and shorten the life, the shaft seal of the oil pump will also be damaged early and cause the pump shaft to leak oil.

(This is the fourth killer of oil pump damage)

7. Change the direction of the oil port: When the direction of the oil port is not suitable and the inexperienced customer adjusts it by himself, the pump core pin is not inserted

Go to the pin hole (caused by pulling out when rotating), then the space of the oil pump suction port is reduced, and the oil suction is blocked, and the oil suction is not smooth. The performance is: noise

Extra large, pressure swing, long-term use will cause the oil temperature to rise too fast, and the life of the stator will be shortened after the curve in the stator is impacted into a corrugated shape. again cutting edges of the seal ring or uneven screw tightening during rotation will also cause oil leakage.

8. Momentary overpressure: There are many times when the oil pump has "cover after collapse", "front cover", "broken shaft", "broken blade",

For extreme accidents such as "cracked stator", a simple judgment seems to be a quality problem of the oil pump. It can be analyzed carefully, but it has another reason.

Because, such as: collapsed double pump rear cover, collapsed single pump front cover, broken shaft, broken blade, broken stator, etc., this situation will not happen at the same time.

When the internal pressure of the oil pump exceeds one or two times the pressure it can bear, the weakest parts in the pump will be damaged first.

The following parts will instantly damage other parts when the power is not stopped, until the broken shaft forces the power to stop and stop.

The damage of other parts is only implicated. Here, the source of the fault is overpressure, and instantaneous overpressure is the culprit of extreme accidents.

The reason for the instantaneous overpressure is that the relief valve that controls the pressure is blocked and cannot be released normally.

In order to understand the pressure limit of the oil pump, we have done several destructive tests, and installed the back covers of several double pumps in a sealed steel

On the board, use a manual pump to gradually increase the pressure. When the pressure reaches 45MPa, the screw will be elongated and the nitrile rubber sealing ring will open. Replace

After installing the fluorine rubber sealing ring and screws, when the pressure reaches 50-55MPa, the rear cover and the front cover respectively cracked.

The above experiment can prove the following phenomena:

a. Qualified hydraulic castings can withstand an internal pressure of 50MPa, and above 50-55MPa is its pressure limit.

b. Four 12.9 level locking screws can withstand the tensile force brought by 45-50MPa.

c. The internal overpressure of the oil pump is the overpressure of the system, not due to human factors, but the oil circuit is blocked.

d. It also requires a lot of pressure to open the sealing ring. There may be internal overpressure or the screw is not locked or the locking is uneven.

e. The pressure limit of the oil pump is 21-32MPa. If there is a phenomenon of cap collapse, it can be affirmed that it is overpressured, and the responsibility lies with the user.

(This is the fifth killer of oil pump damage)

9. Poor oil absorption: A common fault of the vane pump is that the inner surface of the "stator" is worn into a washboard-like rib.

The elephant is mainly caused by poor oil absorption. The reason is: when the oil pump sucks oil insufficiently, the pressure will be high and low, and the top of the blade faces the stator

The effective contact of the inner curved surface will intermittently disengage and contact with the change of pressure. Frequent hard impacts make the oil suction area of the stator easy

There are ribs like a washboard.

Poor oil suction has the following situations: oil is too viscous (the grade is too large), the filter is blocked, the suction pipe is too thin, and the oil level is too high. Low (insufficient oil), etc., this failure occurs more often in winter in the north, because the cold weather cannot absorb the oil.

10. Air leakage at the oil suction port: In the process of a newly installed oil pump, air leakage at the oil suction port is also a common disease, which is characterized by noise

Too big, gurgling, crackling, the higher the pressure, the more obvious, the oil in the tank will foam up after working for a long time. Leaky

The main reason is that the oil pump inlet flange and pipeline seals are not well sealed.

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