1, the definition of vacuum
Vacuum system refers to the state of the rare gas below the atmospheric pressure in the area
2, the degree of vacuum
The degree of vacuum in the thin gas book, usually with "high vacuum" and "low vacuum" to represent. High degree of vacuum means that the degree of vacuum "good", low degree of vacuum means the degree of vacuum "bad."
3, vacuum unit
Usually Torr units, in recent years, the international access to Pa (Pa) as a unit.
1 Torr = 1/760 bar = 1 mm Hg
4, care and conversion of the
1 Torr = 133.322 Pa or 1 Pa = 7.5 × 10-3 Torr
5, the average free path
For irregular thermal motion of the gas particles, the average collision over the success of the two distances, with the symbol "λ" said.
6, traffic
The amount of gas flowing through any section per unit time is indicated by "Q" in units of Pa · L / s or Torr · L / s.
7, guide
Indicates the ability of the vacuum line to pass gas. The unit is liters per second (L / s). At steady state, the duct conductance is equal to the duct flow divided by the pressure difference across the duct. The symbol is marked as "U". U = Q / (P2 - P1)
8, pressure or pressure
The force of the gas molecules acting on the unit area of ​​the container wall is indicated by "P".
9, standard atmospheric pressure
Pressure is 101,325 dynesynes per square centimeter, symbol: (Atm).
10, the ultimate vacuum
After the vacuum container has been fully exhausted, it is stable at a certain degree of vacuum, which is called the ultimate vacuum. Usually vacuum container after 12 hours refining, and then after 12 hours of vacuum, the last hour measured every 10 minutes, whichever is the average of 10 times the ultimate vacuum value.
11, pumping rate
In a certain pressure and temperature, the unit of time from the pump inlet pumped gas called the pumping rate, referred to as pumping speed. That is, Sp = Q / (P-P0)
12, thermocouple vacuum gauge
A vacuum gauge that measures the degree of vacuum by using the principle that the potential of the thermocouple is related to the temperature of the heating element, which in turn is related to the heat conduction of the gas.
13, ionization vacuum gauge (again hot cathode ionization meter)
It consists of a cylindrical collector, a grid and a filament located in the center of the grid. The cylindrical collector is outside the grid. The hot cathode emits electrons to ionize the gas molecules, the ions are collected at the collector, and the gas gauge measures the gas pressure based on the size of the collected ions.
14, composite vacuum gauge
By the thermocouple vacuum gauge and hot cathode ionization gauge, measuring range from the atmosphere ~ 10-5Pa.
15, cold cathode ionization meter
A pair of cathode plates are arranged at the two ends of the anode cylinder. Under the action of an external magnetic field, a vacuum gauge is formed in the anode cylinder to generate ions by the Penning discharge and determine the gas pressure according to the size of the ion current collected by the cathode plate.
16, resistance vacuum gauge
The use of heating element resistance and temperature, the element temperature and the principle of gas conduction, through the bridge circuit to measure the degree of vacuum gauge.
17, Mclaughone vacuum gauge (compression vacuum gauge)
The gas to be tested is compressed with mercury (or oil) to a very small volume, and then an absolute vacuum gauge is calculated directly using the Beer's Law to compare the liquid column difference between open and closed tubes.
18, B-A regulation
This is a cathode and collector inversion of the hot cathode ionization gauge. The collector is a filament placed in the center of the grid, with the filament placed outside the grid, thus reducing soft X-ray effects and extending the lower limit of measurement for ultra-high vacuum.
19, water ring vacuum pump
The pump impeller rotates to create a water ring. As the rotor eccentric rotation and the water ring and the blade between the cyclical changes occurred during the mechanical vacuum pump suction.
20, reciprocating vacuum pump
A mechanical vacuum pump that uses the piston reciprocating motion to pump air.
21, oil seal mechanical vacuum pump
Oil to keep the seal of the mechanical vacuum pump, can be divided into fixed-chip, rotary slice, slide valve type, trochoidal and so on.
22, Roots vacuum pump
A mechanical vacuum pump with a pair of sole-shaped rotors rotating synchronously at high speed. The pump can not be sucked separately. The front stage is equipped with a vacuum pump that can be directly discharged into the atmosphere, such as oil seal and water ring.
23, Turbomolecular vacuum pump
There is a high-speed rotation of the impeller, when the gas molecules and high-speed rotation of the turbine blades were driven to the air outlet and then by the front-stage pump pumping.
24, oil diffusion pump
Diffusion pump nozzle in the high-speed steam jet. In the molecular flow conditions, the gas molecules continue to spread to the steam flow, and the steam to the pump outlet by the compression stage by stage before the exclusion of the pump.
25, low-temperature vacuum pump
Use 20K below the surface of the condensing gas adsorption vacuum pump.
26, cold trap (water-cooled baffle)
Equipment placed between a vacuum vessel and a pump to adsorb gas or trap oil vapor.
27, gas town valve
Oil seal mechanical vacuum pump to open a small hole in the compression chamber, and install the control valve, when the valve is opened and adjust the amount of air intake, the rotor to a position, the air through the hole into the compression chamber to reduce the compression ratio, so that the large Part of the steam does not cause condensation and with the gas is excluded from the pump to play the role of the valve is called the gas valve.
28, vacuum freeze-dried
Vacuum freeze-drying, also known as sublimation drying. The principle is to freeze the material so that the water it contains becomes ice and the ice sublimes under vacuum to achieve the purpose of drying.
29, vacuum evaporation
In a vacuum environment, the material is heated and plated onto the substrate as vacuum evaporation or vacuum coating.
30, vacuum drying
The use of vacuum boiling point under the characteristics of low to dry items method.
31, the common name of the vacuum system
(1) The main pump: In the vacuum system, to obtain the required degree of vacuum to meet the specific requirements of the vacuum pump, such as vacuum coating machine oil diffusion pump is the main pump.
(2) Foreline Pumps: A vacuum pump used to maintain the pressure at the foreline of a vacuum pump below its critical foreline pressure. Such as the Roots pump configuration before the rotary or slide valve pump is the foreline pump.
(3) Roughing Pump: A vacuum pump that starts pumping at atmospheric pressure and pumps the system pressure to another vacuum pump. Such as vacuum coating machine in the valve pump, is the crude oil pump.
(4) to maintain the pump: In a vacuum system, when the gas is small, can not effectively use the foreline pump. To this end configure a smaller auxiliary pump to maintain the main pump work, this pump is called to maintain the pump. If diffusion pump outlet with a small rotary vane pump, is to maintain the pump.