The vacuum gate valve is a special gate valve specially used in vacuum or negative pressure systems. Its core design revolves around ultra-high sealing and low outgassing rate. The working principle and characteristics are as follows:
1. Core definition
Functional positioning
It is used in ultra-high clean environment with vacuum degree ≤1×10⁻⁶ Pa to prevent external gas from penetrating or internal material from outgassing and contaminating the vacuum cavity.
Sealing standard
The leakage rate is strictly controlled at ≤1×10⁻¹⁰ Pa·m³/s (helium leak detection standard), which is far higher than ordinary industrial valves.
2. Key structural characteristics
Sealing system
Adopt all-metal bellows dynamic seal (replace traditional stuffing box) to eliminate micro-leakage caused by valve stem movement.
The contact surface between the gate and the valve seat is mirror polished (Ra≤0.2μm), and the gold-copper alloy sealing ring is used to achieve molecular-level bonding.
Material selection
The valve body is made of 316L ultra-low carbon stainless steel, and the surface area is reduced by electrolytic polishing (reducing gas adsorption).
The bellows is made of Hastelloy C-276 and can withstand ≥100,000 vacuum-atmospheric pressure alternating loads.
Special design
The valve cavity is equipped with an auxiliary exhaust port (KF16 flange interface) to pre-evacuate and balance the pressure difference before opening and closing.
The low-temperature type is equipped with a liquid nitrogen cooling jacket to prevent high temperature from causing the sealing material to deflate.
3. Working mode
Opening process
First start the auxiliary vacuum pump to evacuate the valve cavity to the same level of vacuum as the system (to prevent airflow disturbance).
The bellows drives the gate to rise vertically, and the flow conductivity coefficient is ≥0.95 when the flow channel is fully open.
Closing process
When the gate falls, the limit switch is automatically triggered, and the secondary exhaust is started to ensure that the residual gas in the valve cavity is exhausted.
The contact sealing surface produces a self-tightening effect under the negative pressure of the system. The greater the pressure difference, the tighter the seal.
4. Typical application scenarios
Scientific research equipment
Segmented isolation of particle accelerator vacuum beam pipelines (such as the European Organization for Nuclear Research LHC). Undulator vacuum protection valve for synchrotron radiation source.
Industrial equipment
Reaction chamber injection control for semiconductor ALD coating machine.
Emergency isolation valve for spacecraft thermal vacuum test chamber.
Special field
Vacuum isolation of the first wall cooling system of nuclear fusion device (such as ITER).
Sample transfer channel sealing of lunar dust simulation chamber.
5. Performance indicators
Temperature range: -196℃ (liquid nitrogen cooling) to 450℃ (high temperature baking type).
Diameter range: DN10 micro valve to DN800 large vacuum lock chamber.
Operation mode: manual worm gear drive, pneumatic fast opening (response time <1s), electric stepping control (positioning accuracy 0.01mm).
6. Maintenance points
Helium mass spectrometry leak detection is required after every 1000 operations, and the bellows assembly needs to be replaced if the leakage rate exceeds the standard.
The contact sealing surface needs to be re-polished every 5 years to restore the surface finish.
It is forbidden to use acetone and other organic substances for cleaning. Plasma dry cleaning is recommended.