The noise and vibration of water ring vacuum pump will increase in a short period of time under cavitation condition, and even cause damage to the pump. Therefore, large quantity should be taken to prevent the operation of water ring vacuum pump under cavitation state. The following steps can be taken.

1. Increase the heat of the water

Because the vacuum pump freezing water temperature rise will lead to a significant increase in its pumping energy, the vacuum pump seal water temperature must be lower than the corresponding saturated heat of exhaust pressure, otherwise the vacuum will be improved, and the cavitation erosion of the vacuum pump impeller will be caused. Therefore, the idea of preventing cavitation is to increase the heat of water.

2. Popularize the accuracy of type selection, make the vacuum pump run in the insurance area

In the selection stage, the vacuum pump suction pressure and the heat of water should be selected to avoid the pressure scale of the vacuum pump which produces cavitation, that is to prevent the vacuum pump from operating in the sea area of critical vacuum degree or critical exhaust pressure, and the excessive volume will aggravate the cavitation.

3. Device cavitation shield pipe

For the vacuum pump equipped with cavitation shield pipe, the bubbles generated in the cavitation will break when compressed. The introduction of non condensable gas with high pressure from inside can timely supplement the space emerging due to bubble rupture, which can greatly increase the harm of cavitation to the pump and increase the noise and vibration caused by cavitation.

Some pumps have cavitation protection interface, such as working under the limit pressure, opening the cavitation shield pipe interface (or connecting with the steam water connector) can eliminate the cavitation sound under the condition of maximum protection of suction idea, and inherit the protection for the pump.

4. Equipped with atmospheric injector

The function of the atmospheric ejector is to use the pressure difference between the atmospheric pressure and the vacuum pump to generate atmospheric jet, which loses the suction pressure lower than that of the vacuum pump in the ejector, so as to eliminate the limit pressure of the vacuum pump, prevent the cavitation of the vacuum pump, and play the role of protecting the vacuum pump. Because the atmospheric ejector is set to prevent the cavitation of vacuum pump and protect the vacuum pump, the vacuum formed by suction is better than that without air ejector.

5. Use a lower saturated vapor liquid as the working fluid

When the working fluid is changed from water to transformer oil, the limit vacuum degree of the oil will lose a higher improvement due to the lower saturated vapor pressure of the oil. In the process of removing the larger purified gas and in some special occasions, the working fluid of vacuum pump can also be used with other liquids (such as propanol, ethanol, xylene, aniline, amphetamine hydrochloride and other organic solvents with low viscosity). The limit vacuum degree is determined by the saturated vapor pressure of the working fluid.

The oil ring vacuum pump can be operated at 20 ~ 90 ℃, so it is not easy to condense the steam due to the high oil temperature when extracting the gas such as steam, so the pump oil is not easy to be emulsified, thus popularizing the service life of the pump oil. When using organic solvent as working fluid, attention should be paid to whether the motor is explosion-proof and corrosion of vacuum pump and its seals.

6. The impeller and disc of the pump adopt materials with strong anti cavitation power

It is recommended that low carbon chromium nickel alloy steel, such as 13cr4n, has good anti erosion performance as hydraulic machinery materials for operation under cavitation condition. The process of impeller coating is rare, and non-metallic coating adopts epoxy resin, nylon powder, polyurethane, etc. In addition, the idea of preventing cavitation damage has also been obtained, such as stainless steel wire surfacing method, stainless steel plate inlay welding repair method, alloy powder spray welding.

Compared with the number of steps of nonmetal and alloy (including stainless steel), the non-metallic coating is economical in form, but the operation process should be controlled widely to prevent the coating from falling off. The idea of adopting alloy powder spray welding is good, but the profit is high, and some centers may have no choice but to inherit.