1、 Pneumatic ultra-high vacuum gate valve overview:
The electric ultra-high vacuum gate valve drives the valve stem through the electric device to drive the valve plate to move up and down to open or close the valve. The valve is used to connect or cut off the airflow in the vacuum pipeline. The applicable medium is pure air and non corrosive gas.
Main parts and materials of electric ultra high vacuum gate valve with feedback signal device
Valve body and valve plate: stainless steel
Seals: fluororubber, bellows (shaft seal), nitrile rubber.
2、 Outline and connection dimension of pneumatic ultra-high vacuum gate valve (mm)
In the vacuum system, the vacuum system elements used to change the air flow direction, adjust the air flow, cut off or connect the pipeline are called vacuum valves.
Vacuum valve has the following characteristics:
The pressure is lower than atmospheric pressure, and the pressure drop on the disc cannot exceed 1 kgf / cm2. The working temperature of the medium depends on the process of using the device. The temperature generally does not exceed the range of – 70 to + 150 ℃.
The most basic requirement for this kind of valve is to ensure the high tightness of the connection and the compactness of the structure and gasket material.
According to the medium pressure vacuum valve can be divided into four groups:
1) low vacuum valve: medium pressure p=760~1 mm Hg;
2) medium vacuum valve: p=1 * 10-3 mmHg.
3) high vacuum valve: p=1 x 10-4 ~1 x 10-7 mmHg;
4) ultra high vacuum valve: P less than 1 x 10-8 mmHg.
As a closed-circuit valve with a diameter less than 250mm, the widely used valve stem is a vacuum bellows stop valve with a linear motion. However, gate valve is limited greatly, which is mainly for large diameter. Also available are ball cock (ball valve), plunger valve and butterfly valve. The plug valve used as a vacuum valve has not been popularized because the plug valve needs to be lubricated with oil so that oil vapor may enter the vacuum system, which is not allowed. The vacuum valve can be controlled by hand and remote control on site, as well as electric, electromagnetic drive (solenoid valve), pneumatic and hydraulic control.
Vacuum valve closures are sealed with rubber or metal seals. Bellows of bellows stop valve are made of stainless steel, high zinc brass ji80, plastic and other materials. Diaphragm seal can be used for small diameter (diameter less than 10 mm) stop valve closure. Ball cock can be used for low vacuum and medium vacuum.
Vacuum valve in vacuum system function
1. Switch on and off the air circuit. When valve 1 and valve 4 are closed and valve 2 is open, the mechanical vacuum pump III of Sanchi valve vacuumizes the container I and the air flows through the pre vacuum extraction pipeline; when valve 2 is closed and valve 4 is open, the mechanical pump can vacuumize the diffusion pump alone; when valve 1 and valve 4 are open at the same time, the diffusion pump and the mechanical pump can work at the same time to vacuumize the container, and the air flows through the diffusion pump at this time. It can be seen that the role of the valve in this operation is to switch on and off the air path and change the flow path of the air flow.
2. Control the air flow and adjust the vacuum degree. In Figure 1, the opening angle of the valve cover of regulating valve 1 can adjust the air flow through the pipeline; close valve 2 and valve 4, and the inlet of mechanical pump III can be put into the atmosphere through vent valve 3; and the true air degree in the container can be adjusted through vent valve 5.
3. For quantitative inflation, three branch valves have a small hole with a certain volume on the plunger of the glass valve. When the small hole is turned to the right and connected with the high-pressure gas cylinder, the small hole can be filled with high-pressure gas; when it is turned to the left and connected with the vacuum container, the high-pressure gas of this volume is put into the container, which plays the role of quantitative inflation.
There are many kinds of vacuum valves, which are usually classified according to their functions, structural types, driving methods, materials and applications.