Oil seals (also called shaft seals) in vane pumps and oil pumps usually have a pressure resistance limit of about 2 kg. If this pressure is exceeded, the oil seals will open outward, resulting in oil leakage from the shaft head. The seals are relatively strict. High-pressure oil generally does not flow to the oil seal in the low-pressure area, and part of the oil leaking from the screen to the oil seal will also flow from the shaft end to the low-pressure oil inlet chamber through the shaft hole. The shaft seal is always at zero. In the pressure state, only the seal itself has a problem or the oil seal assembly fails to cause the oil seal to leak oil. In practical applications, strange oil seal leakage has become a common fault in oil pumps, but it has not been found after inspection. Reasons for seal failure or improper installation, then, many kinds of oil seal leaks have become difficult to understand. In the past, everyone did n’t know enough about oil seal leaks. Customers and manufacturers complained to each other. No one can explain the real oil leak. The reason can only be simple oil seal replacement or the entire oil pump returned to the original factory for repair. The result of this treatment has increased the economic burden on customers and manufacturers, and has also increased both parties. In order to solve this problem, Zhejiang Yongling Hydraulic Machinery Co., Ltd. & China Vane Pump Company conducted in-depth analysis in theory and technology and actual experience to truly find out the reason for oil leakage in the oil seal for your reference.

First of all, we must confirm that the oil seal is opened outward, the spring leaks, and the oil seal skeleton is weak. In this case, oil leakage is the object of focus today, and other oil leakage methods are not among them. The damage degree of this kind of oil seal is worse than oil leakage. It is also the most difficult to understand.

After analysis, there is only one reason for the oil seal to open outward, that is, the interior encountered a strong pressure (more than 2 kg), and the high pressure oil flowed to the oil seal. The first thing to check is how it can enter the low pressure area. Does the high pressure seal fail, and if the seal does not fail, how does the high pressure oil come in?

After a long period of exploration, professional and technical personnel used the principle of oil pump sealing to back up and treat the phenomenon that should not be established as a fact. Finally, they found the crux of the problem, and theoretically derived the principle of the oil seal leaking outwards.

This outward expansion must meet three conditions at the same time. One is indispensable, and the other cannot be established. This is:
1. The oil inlet of the vane oil pump must be equipped with a check valve. The oil can only be sucked in and not drained back to the tank.
2. There must be no check valve installed at the oil outlet of the vane oil pump.
3. The vane oil pump must be just stopped.

The reason is that when the oil pump just stopped, the system load was very strong, and the pressure oil instantly reversed into the inside of the vane pump. When the vane of the vane pump just retracted due to the shutdown, the high and low pressure oil chambers also just channeled. The high-pressure oil return is blocked by the check valve at the oil inlet and cannot be unloaded effectively. The pressure oil is forced from the center hole of the low-pressure area of ​​the pressure side plate to the oil seal. In this way, the oil seal is suddenly outward opened.

Reasons for the installation of check valve at the suction port. If the suction pipe is long or installed vertically, the remaining oil in the pump will be drained back to the tank after the pump is stopped. When the pump is restarted, it will damage the pump due to difficulty in sucking oil. Installing a check valve will keep the oil in the oil pump or pipeline in place, which will facilitate re-oiling.

The reason for installing a check valve at the oil outlet is that if the system is stopped under pressure, the system still maintains high pressure, and the oil pump is unable to withstand pressure due to low speed. The strong oil return pressure will damage the oil pump. Install an oil pump The outlet check valve is to block the high-pressure oil at the check valve and prevent it from flowing back to protect the safety of the oil pump.

The vane pump is in close contact with the stator at normal speed or under a certain pressure. At this time, the high and low pressure oil chambers in the pump are closed to each other. When the speed drops to a certain speed, the pressure is low When it is not enough to eject the blades, the blades retract to the bottom of the rotor, and the high and low pressure oil chambers in the pump pass through.

When the above three conditions are met at the same time, it is necessary to open the oil seal. If the oil return pressure is not so high (how high cannot be calculated), if the stopping speed does not decrease so fast, if there is a check valve at the outlet, if oil is sucked Without a one-way valve at the port, the oil seal cannot be broken apart.

In order to prevent the oil pump from damaging the oil pump due to high-pressure backflow, install an outlet check valve, and the oil inlet and check valve may be optional as required. After these measures are in place, the accident of the oil seal opening outward can be effectively avoided. .

 

Zhejiang Yongling Hydraulic Machine Co , Ltd  is a professional China manufacturer and supplier specializing in the production of    Vane Pumps  . View vane pump product information and related information, welcome to visit: https://www.china-vanepump.com