Knowledge – Vacuum Valves

I. Introduction of valve
Vacuum valve is a vacuum system component used to change the direction of airflow, adjust the size of gas flow, cut off or connect the pipeline in the vacuum system. The closing parts of the vacuum valve are sealed by rubber seal or metal seal.

II. Common vacuum valve applications.
Vacuum valves
Used in high or ultra-high vacuum system equipment when vacuum must be maintained in a closed vacuum handling system. Vacuum valves are used to control the air flow into the vacuum chamber, isolate, vent, provide pressure reduction or control conduction. Gate valves, Inline valves and angle valves are the most common types of vacuum valves used for high or ultra-high vacuum applications. Additional valve types include butterfly valves, transfer valves, ball valves, pendulum valves, all-metal valves, vacuum valves, aluminium angle valves, Teflon-coated vacuum valves and straight-through valves.

Butterfly valves
are fast opening valves consisting of metal discs or vanes that pivot at right angles to the direction of flow in the pipeline and when rotated on their axis, the valve seals the seat in the valve body.

Transfer valves (rectangular gate valves)
Separation valves suitable for use between load-locked vacuum chambers and transfer chambers, and between transfer chambers and processing chambers in semiconductor manufacturing equipment.

Vacuum Ball Valves
are quarter turn straight flow valves with a circular closure assembly with matching circular seats for uniform sealing stress.

Pendulum valves
is a large throttle valve fitted between the process vacuum chamber and the turbomolecular pump inlet. These vacuum pendulum valves are typically designed as gate or pendulum valves for applications including OLED, FPD and PV industrial manufacturing systems.

All-metal valves
Designed for use in ultra-high vacuum environments where high temperatures do not allow the use of elastomers and cryogenic gasket metals. Bakeable all-metal valves provide reliable high temperature sealing from atmospheric pressure to below 10-11 mbar.

Vacuum valves
Operate reliably in semiconductor production systems and in applications with chemical and particulate contamination. They can be used in rough vacuum, high vacuum or ultra-high vacuum environments.

Aluminium angle valves
The inlet and outlet of these valves are at right angles to each other. These angle valves are made of aluminium A6061-T6 and are used in semiconductor and instrumentation manufacturing, R&D and industrial vacuum systems for rough to high vacuum applications.

The Teflon coated vacuum valve is a fully engineered stainless steel vacuum component device with a durable and highly chemical resistant coating.

III. Characteristics of vacuum valves.
The pressure is below atmospheric pressure and the pressure drop across the valve flap cannot exceed 1 kg force/cm. The working temperature of the medium depends on the process of the device used. The temperature generally does not exceed the range of -70 ~ 150°C. The most basic requirement for such valves is to ensure a high degree of tightness of the connection and the denseness of the structure and gasket material.

According to the medium pressure vacuum valves can be divided into four groups.
1) Low vacuum valves: medium pressure p=760~1 mmHg.
2）Medium vacuum valves: p=1×10-3 mmHg.
3）High vacuum valves: p=1×10-4 ~1×10-7 mmHg.
4）Ultra-high vacuum valve: p≤1×10-8 mmHg.

As a closed-circuit valve with a passage diameter of less than 250 mm, the widely used stem is a vacuum bellows shut-off valve with linear movement. Gate valves, however, are more restricted, but this is mainly for large diameters. Also available are spherical plug valves (ball valves), plunger valves and butterfly valves. Plug valves for vacuum valves have not been promoted because they require oil lubrication, making it possible for oil vapour to enter the vacuum system, which is not allowed. Vacuum valves can be controlled manually and remotely in the field, as well as electrically, electromagnetically (solenoid valves), pneumatically and hydraulically.