Design principles and selection considerations for vacuum valves.

The design principles of vacuum valves should generally include the following points.

1. The sealing performance of the valve is good, not only means the leakage rate at the closed position of the valve plate need to be small, but also the leakage rate of the valve body needs to be small;

2. The valve sealing components have good wear resistance, especially the valve seat and valve plate sealing components that can be reused and have a long service life;

3. The conductivity of the valve should be large;

4. Valve materials should have low saturated vapor pressure, high corrosion resistance, and high chemical stability;

5. Ultra high vacuum valves should be resistant to baking, with a baking temperature generally not less than 150 ℃ and a maximum of 450 ℃;

6. The valve structure should be simple, the appearance should be beautiful and generous, the switch should be light and flexible, the switch status should be marked, and large valves should have lifting devices, which are easy to operate and maintain;

7. The processing technology of valve components is good, and the surface treatment process is advanced. The valve connecting flange should comply with the national standard requirements for vacuum flanges. 

The main considerations when selecting vacuum valves are as follows:

1. The applied vacuum area;

2. The pressure difference on both sides of the valve when closed;

3. Leakage rate of the valve;

4. Capable of withstanding baking temperature;

5. Capable of withstanding ambient temperature;

6. Lifetime measured by opening/closing times;

7. If it is an ultra-high vacuum metal valve, it is also necessary to know its allowable heating and cooling rates.