The noun explanation about vacuum
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1. Definition of vacuum
A vacuum system is a thin volume of gas below the atmospheric pressure in the area.
2. Vacuum degree
The degree of thinness in a vacuum is usually expressed as "high vacuum" and "low vacuum". A high vacuum means good, and a low vacuum means poor.
3. Vacuum unit
Usually Torr is used as the unit, and Pa is used internationally in recent years.
1 holder = 1/760 atmosphere = 1 millimeter of mercury
4. Transfer between Tod and pa
1 pallet = 133.322 pallets or 1 pallet = 7.5 times 10-3 pallets
5. Average free path
The mean distance passed by two successive collisions of gas particles in unregular thermal motion is denoted by the symbol "departure".
The quantity of gas flowing through any section in unit time, expressed as "Q", in units of Pa·L/s (Pa·L/s) or Torr·L/s (Torr·L/s).
7. Flow guide
It’s the ability of a vacuum pipe line to pass through a gas. The unit is liters per second (L/s), and in a steady state, the pipe flow is equal to the pipe flow divided by the pressure difference between the two ends of the pipe. The symbol is called U.
U = Q/(P2, P1)
8. Pressure or pressure
The force applied by a gas molecule per unit area of the wall of the container is expressed as P.
9. Standard atmospheric pressure
Pressure of 101325 dain per square centimeter, symbol :(Atm).
10. Ultimate vacuum
After the vacuum vessel is fully pumped, it is stabilized at a certain vacuum degree, which is called the ultimate vacuum. Usually, the vacuum vessel must undergo air refining for 12 hours and then vacuum for 12 hours. The final hour is measured every 10 minutes. The average value of 10 times is taken as the limit vacuum value.
11. Pumping rate
At a certain pressure and temperature, the gas pumped from the pump inlet in unit time is called the pumping rate, or the pumping rate. Sp = Q/ (p-p0).
12. Thermocouple vacuum gauge
A vacuum gauge used to measure the degree of vacuum by using the electric potential of the thermocouple in relation to the temperature of the heating element, and the temperature of the element in relation to the heat conduction of the gas.
13. Ionization vacuum gauge (hot cathode ionization gauge)
It is composed of a tubular collector pole, a grid and a filament located in the center of the grid. The tubular collector pole is outside the grid. Hot cathode emission electron ionized gas molecules, ions are collected by the collector, according to the collected ion stream size to measure the gas pressure of the vacuum meter.
14. Composite vacuum gauge
Consisting of a thermocouple vacuum gauge and a hot-cathode ionization vacuum gauge, the range of measurement is ~ 10-5pa.
15. Cold cathode ionization gauge
There is a pair of cathode plates at both ends of the anode tube, under the action of external magnetic field, pannin discharge is formed inside the anode tube to produce ions, and the vacuum meter of gas pressure is determined according to the size of ion flow collected by the cathode plate.
16. Resistance vacuum gauge
A vacuum gauge that measures the vacuum degree by means of a bridge circuit, using the principle that the resistance of the heating element is related to temperature and the temperature of the element is related to gas conduction.
17. McLeod vacuum gauge (compressed vacuum gauge)
The gas to be measured is compressed to a very small volume with mercury (or oil), and then compared to the liquid column difference between open and closed tube.
18 and B - A gauge
This is a hot cathode ionization gauge with a collector inversion. The collector electrode is a filament, placed in the center of the grid, and the filament is placed outside the grid, thus reducing the impact of soft X-ray.
19. Water ring vacuum pump
The pump impeller rotates to produce a water ring. It’s a mechanical vacuum pump, pumps air due to the periodic change of the volume between the water ring and the blade due to rotor eccentricity rotation.
20. Reciprocating vacuum pump
It’s a mechanical vacuum pump, draws air by the reciprocating movement of the piston.
21. Oil seal mechanical vacuum pump
Mechanical vacuum pump with oil to keep the seal can be divided into fixed type, rotary type, sliding valve type, trochoidal type and so on.
22. Roots vacuum pump
Mechanical vacuum pump with a pair of synchronous high-speed rotating-shoe rotors, this pump can not be separately pumped, oil seal, water ring and other vacuum pumps can directly exhaust the atmosphere.
23. Turbo-molecular vacuum pump
There is a high-speed rotating impeller. When the gas molecules collide with the high-speed rotating turbine blade, they are driven to the outlet and then removed by the front pump.
24. Oil diffusion vacuum pump
A high - speed steam stream is ejected from the nozzle of the diffusion pump. Under the condition of molecular flow, the gas molecules are continuously diffused into the steam flow, and are compressed by the steam belt to the outlet of the pump step by step and then excluded by the former pump.
25. Low temperature vacuum pump
The vacuum pump used to condense the adsorption gas on the low temperature surface under 20K.
26. Cold trap (water baffle)
A device placed between a vacuum container and a pump to absorb gas or capture oil vapour.
27. Air ballast valve
Mechanical oil seal vacuum pump on the compression chamber to open a small hole, and put on the regulator, and adjust the volume when open the valve, the rotor to a particular location, passed this hole with compressed air chamber to reduce compression ratio, so as to make the most of the steam is condensed from the locked out of the pump with mixed gas in the role of the valve is called the gas ballast valve.
28. Vacuum freeze drying
Vacuum freeze drying, also known as sublimation drying. The idea is to freeze the material so that the water it contains turns into ice, then sublimate the ice in a vacuum to dry out.
29. Vacuum evaporation
In a vacuum environment, heating and coating the material onto the substrate is called vacuum evaporation, or vacuum coating.
30. Vacuum drying
It’s a method of drying articles by using the low boiling point in a vacuum environment.
31. Common name for vacuum system
(1) main pump: in the vacuum system, the vacuum pump used to obtain the required vacuum degree to meet the specific process requirements, such as the oil diffusion pump in the vacuum coating machine is the main pump.
(2) front stage pump: the vacuum pump used to maintain the pressure of a vacuum pump at the front stage below its critical front stage. A rotary vane or slide valve pump, as in the case of a roots pump, is a forepump.
(3) rough pump: the vacuum pump that starts to pump air under atmospheric pressure, and then pumps the system pressure to another vacuum pump to start work. Such as vacuum coating machine in the sliding valve pump, is coarse oil pump.
(4) maintenance pump: in the vacuum system, the air volume is very small and the front pump cannot be effectively utilized. To this end, a small capacity of the auxiliary pump to maintain the main pump work, this pump is called maintenance pump. If a small rotary vane pump is provided at the outlet of the diffusion pump, it is the maintenance pump.