1. Select the valve type based on the vacuum level

The first principle in valve selection is vacuum level matching. Under different vacuum ranges, there are significant differences in gas flow state, leakage sensitivity, and material outgassing behavior. If the valve level is insufficient, it will become a performance bottleneck for the entire system.

Low vacuum/medium vacuum system (≥1 Pa)：Rubber-sealed valves, such as KF quick-release valves, soft-sealed butterfly valves, and soft-sealed angle valves, can be selected. These valves are low-cost, fast-opening and closing, and easy to maintain, making them suitable for industrial applications such as packaging, vacuum drying, and adsorption systems. 

High vacuum system (0.1 Pa to 10⁻⁵ Pa)：High vacuum valves, such as ISO flange angle valves, gate valves, and flapper valves, must be selected. They typically employ fluororubber (FKM) or composite sealing structures, featuring low leakage rates and minimal outgassing, and are capable of meeting the requirements of molecular flow conditions. 

Ultra-high vacuum system (≤10⁻⁵ Pa):Fully metal-sealed valves (CF flange, knife-edge seal) are required. These valves can withstand high-temperature baking and exhibit almost no outgassing, making them a must-have solution for UHV systems.

Conclusion: The vacuum level of the valve must be at least one order of magnitude higher than the system design vacuum level. 

2. The role of vacuum valves in vacuum systems 

In a vacuum system, the components used to change the direction of airflow, adjust the magnitude of airflow, and cut off or connect pipelines are called vacuum valves. The functions of vacuum valves in a vacuum system are: switching air paths, changing the flow route of airflow; controlling the magnitude of airflow, adjusting the vacuum degree; and quantitatively inflating. When configuring and selecting vacuum valves, it is necessary to consider the minimum pressure difference and high flow resistance of components within the molecular flow range. In addition, the valve body and valve seat require the minimum leakage rate. The lubricant on the vacuum side of the moving parts in the valve must be suitable for the required pressure and temperature range, or the overall exposure to high or ultra-high vacuum should be avoided as much as possible. The minimum harmful (dead) space and large flow conductance are important, especially in the molecular flow range.

3. Types of vacuum valves 

The main performance indicators of a vacuum valve include its conductance, leakage rate, accuracy and reliability of its opening and closing actions, as well as its opening and closing time. There are many types of vacuum valves, and the selection of vacuum valves during the design of a vacuum system depends on factors such as application, size, performance, and structure. Domestic vacuum valves are classified according to their performance structure, drive method, channel type, channel diameter, material, and application 

1. Vacuum gate valve

Structural Features: The gate plate moves vertically along the centerline of the valve seat. When fully opened, the flow passage is straight through, resulting in minimal flow resistance and low pressure loss.

2. Vacuum ball valve

Structural Features: The ball rotates 90° around the centerline of the valve body to achieve opening and closing. It has good sealing performance, quick switching, and easy operation.

3. Vacuum butterfly valve

Structural Features: The butterfly plate rotates around the valve shaft. When opened, it allows almost full flow. When closed, the butterfly plate seals with the valve seat. The structure is simple, compact, and lightweight.

4. Vacuum diaphragm valve

Structural Features: The valve uses a diaphragm as the opening and closing component. The diaphragm separates the inner cavity of the valve body from the inner cavity of the valve cover, achieving sealing through diaphragm deformation, eliminating the risk of leakage.

5. Vacuum flapper valve

Structural Features: The valve plate achieves sealing through the up-and-down or left-and-right movement of the valve rod, and offers various driving modes such as manual, electric, and pneumatic.

6. Vacuum gate valve

Structural Features: The valve plate and valve seat achieve sealing through tight fitting, with diverse driving methods. It features high flow conductivity, good sealing performance, and low blow-by rate.

7. Vacuum shut-off valve

Structural Features: The valve stem axis is perpendicular to the valve seat sealing surface, with a short opening or closing stroke, reliable shut-off action, and adjustable flow rate.

8. Vacuum angle valve

Structural Features: The inlet and outlet are arranged at right angles, featuring high air tightness and durability against dirt. The mechanical drive components are located outside the vacuum range, facilitating lubrication.

8. Vacuum slide valve

Structural Features: The valve plate slides along the valve body to achieve opening and closing. The section is open, the installation depth is low, and it has good sealing performance and vibration resistance.

9. Vacuum control valve

Structural features: Precise control of valve opening through electric or pneumatic means, enabling automatic adjustment of gas flow or pressure.