Differences between vacuum globe valves and ordinary globe valves

Vacuum valves have the following characteristics: the pressure is below atmospheric pressure, and the pressure drop across the valve disc must not exceed 1 kilogram-force per square centimeter. The operating temperature of the medium depends on the process of the device in use. The temperature generally does not exceed the range of -70 to +150°C. The most basic requirement for such valves is to ensure a high degree of sealing at the connections, as well as tightness in the structure and gasket materials. Vacuum valves can be divided into four groups according to the medium pressure: 1) Low-vacuum valves: medium pressure p = 760~1 mmHg ； 2) Medium vacuum valve: p=1×10-3 mmHg. 3) High-vacuum valves: p=1×10-4 ~1×10-7 mmHg ； 4) Ultra-high vacuum valves: p≤1×10-8 mmHg. A vacuum diaphragm globe valve, in which a valve stem that moves linearly is widely used. Gate valves are subject to greater limitations, but for larger diameters, ball valves, plug valves, and butterfly valves are also available. Plug valves used for vacuum valves have not been widely adopted, as they require oil lubrication, which can allow oil vapor to enter the vacuum system, and this is not permitted. Vacuum valve shut-offs are sealed using rubber seals or metal seals. The bellows of bellows-type stop valves are made of stainless steel, high-zinc brass JI80, plastics, and other materials. Diaphragm seals can be used for the closing elements of globe valves with small bore sizes (under 10 millimeters). Spherical stopcock valves can be used for low vacuum and medium vacuum.