Vane valve for vacuum pump

1. working principle of pneumatic valve:

The pneumatic valve is set for the removal of condensable gas by rotary vane vacuum pump. Usually the gas removed by the pump is a mixture of permanent gas and condensable gas. In the process of compression and exhaust, when the partial pressure of condensable gas exceeds the saturated vapor pressure of the gas corresponding to the pump temperature, condensable gas will coagulate and mix in the pump oil. The oil circulates with the pump and vaporizes again when it returns to the high vacuum side. This will affect the pumping performance of the pump. Increase the pollution of pump oil.

Gas ballast valve or the aeration method can effectively prevent the non-condensable gas condensation, namely in the compression process through the control of a permanent gases (usually a room temperature drying air) by the air holes with compressed gas, causing the non-condensable gas partial pressure pump has not been achieved before the temperature corresponding to the saturated vapor pressure, the pressure of compressed gas has reached exhaust pressure, exhaust valve opens. Condensable gas together with permanent gases expelled. Mechanical vacuum pump oil seal type is generally equipped with a gas ballast device, so also called gas ballast pump.

The valve consists of throttle valve and reverse check valve. The throttle valve controls the most aerated gas, and the reverse check valve prevents backflow when the gas pressure in the pump cavity is higher than the aerated pressure. There are two kinds of setting of air hole position: one is near the pump exhaust port, when the compressor cavity is connected with the exhaust port, the air is added. Another is set up on the end cover, when inspiratory, “at the end of the rotor to turn an Angle (10 ° ~ 15 °), air hole, began to aeration. In the course of aeration. The extreme pressure of the pump will go up and the pumping rate will go down. At low pressure, the valve can be opened properly, and a small amount of gas can be added to reduce the noise caused by the pump oil shock exhaust valve.

2. Structure of pneumatic valve:

On the structure, gas ballast valve a non-return valve, prevent exhaust when oil, gas from the air hole, air quantity is designed to be adjustable, can obtain different limit of town gas pressure, gas ballast valve open to move to the appropriate location, outside the pump can realize long-distance operation. The valve can reduce the noise when it is slightly permeated, and it can also be used as the release valve when the pump is stopped to avoid or delay the return oil of the pump.

3. Functions of the pneumatic valve:

Various vapors or mixtures of vapors and gases are often discharged in vacuum applications, mainly steam. Ordinary rotary vane vacuum pumps can’t be ruled out steam, steam into rotary vane pump after the studio will be compressed, the pressure increase gradually to the saturated vapor pressure (saturated vapour pressure of water vapor in 20 ℃ 2.3 x103Pa, at 60 ℃ for 2 x104pa), exhaust valve is not opened, excess vapor began to condense into liquid, and vapor line not to go out.

If the steam is corrosive, the pump body will soon be seriously corroded. In order to avoid the influence of condensation water on the pump performance, the most simple and effective way is by air to prevent the steam condensation in good KaiDeXuan rotary pump, namely in the compression space adjustable one part by one of the mixed gas mixing valve (that is, the gas ballast valve).

When the pump works, a certain amount of gas is added into the valve compression space to mix it with the steam. Before the steam condenses during the compression, the pressure of the mixture exceeds 0.1mpa, so the exhaust valve can be pushed out of the pump and the steam can be eliminated. The amount of gas added depends on the amount of steam.

Although steam can be removed through a pneumatic valve, it can reduce the limit vacuum of the pump by an order of magnitude. Therefore, in practical use, when steam is removed, the valve should be closed in time.

4. Pneumatic valve fails:

1. The connection between the pneumatic valve and the fuel tank (or pump cover or pump body) fails to seal, causing external leakage.

2. The reverse check valve of the pneumatic valve is invalid. The pump oil leaked out when the gas was released.

3. The reverse check valve of the pneumatic valve cannot be stopped when it stops the pump, and when the oil returns to the pneumatic valve, if the gas cap is not closed, it can cause the oil leakage of the rotary vane vacuum pump.

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