What Is a Vacuum Valve?
Vacuum valves are installed in devices such as vacuum chambers where the gas pressure inside and outside differs. Closing the valve maintains the vacuum in the chamber and shuts off outside air. Opening the valve returns the chamber to atmospheric pressure.
In some cases, the amount of gas flowing into the chamber can be adjusted, or pumps can be connected to each other with vacuum valves. There are many types of equipment, ranging from equipment for research to manufacturing.
In recent years, vacuum equipment has become larger and larger, and there is a growing demand for products with larger vacuum valve mouths.
Applications of Vacuum Valves
There is a line-up of vacuum valves ranging from those for atmospheric pressure to those for ultra-high vacuum. The appropriate type of vacuum valve depends on the required vacuum level and application, so it must be selected appropriately.
Vacuum valves are used in vacuum chambers and pumps for semiconductor manufacturing and other applications. They are also used in machines where the pressure of various gases is changed. They are incorporated into machines for a variety of applications, including molding automotive parts, dehydration and concentration of pharmaceuticals and chemicals, degassing and gas displacement packaging, depressurization, and sterilization.
Principle of Vacuum Valves
By opening and closing, vacuum valves control the pressure difference between the atmosphere and the chamber. It uses bellows to distribute the force to withstand the pressure when closed. The valve is mainly manually opened and closed by a pneumatic drive system.
They are made of stainless steel, aluminum, or other materials for vacuum use and can withstand high-temperature heating. Vacuum valves are also available in reverse pressure and positive pressure versions. Reverse pressure seals the valve plug from the vacuum side to the atmosphere side, and positive pressure does the opposite, sealing it from the atmosphere side to the vacuum side.
There are two main types of vacuum valve usage, each using different types valves.
1. Shutoff Valve
A shutoff valve separates the atmosphere from the vacuum, and most vacuum valves are shutoff valves. It separates and seals the different pressure spaces of the vacuum and atmosphere. Types include gate valves, L-shaped valves, and straight valves.
2. Gas Volume Control Valves
There are two types of valves: variable leak valves, which finely adjust the amount of gas flowing into the vacuum chamber, and conductance valves, which are placed between the vacuum chamber and the vacuum pump to adjust the pumping speed. Conductance valves are available as needle valves and butterfly valves.
Structure of Vacuum Valves
A vacuum valve consists of an insulating container, flange, arc shield, bellows, fixed electrode rod, movable electrode rod, and contacts.
The contacts are opened and closed by the movement of the movable electrode rod while maintaining a vacuum through the bellows.
Arc shields are placed around the contacts to detect metal vapor generated between the fixed and movable contacts when the current is interrupted.
This prevents damage to the insulation performance inside the insulating vessel.
Vacuum valve contacts are available in a variety of configurations, including flat-plate, spiral, and longitudinal magnetic field contact configurations.
The flat plate contact structure literally means that the contact part consists of a flat plate, but when the contact is a simple flat plate, problems arise, such as the buildup of heat due to arcing.
To solve these various problems, contact structures, such as spiral contacts and vertical magnetic field contact structures, have been developed.
The spiral contact structure is a contact structure that suppresses the generation of localized heat due to arcing by means of a special spiral structure.
The longitudinal magnetic field contact structure applies a parallel magnetic field to the arc by means of a coil configured at the back of the contact.
The structure of vacuum valves has evolved through the development of contact materials with superior shutoff performance and withstand voltage, the development of contact structures, research on dielectric breakdown phenomena, observation of arc behavior, electromagnetic field analysis technology, manufacturing process technology, and other new technologies. The size and performance of vacuum valves have been reduced by about 6% in volume over the past 40 years.
Global Market for Vacuum Valves
The global demand for vacuum valves is driven by the rapid expansion of the IT market, investments in modernizing other industrial facilities, and rising demand for a variety of products. The global market for vacuum valves is expected to grow at a rapid pace in the coming years, with projections indicating an increase of $500 million between 2020 and 2024.