A vacuum pump refers to a device or equipment that uses mechanical, physical, chemical, or physical-chemical methods to evacuate the pumped container to obtain a vacuum. In layman's terms, a vacuum pump is a device that uses various methods to improve, generate and maintain a vacuum in a closed space.
With the development of vacuum applications, many types of vacuum pumps have been developed, and their pumping speeds range from a few tenths of a liter per second to hundreds of thousands and millions of liters per second. In the field of production and scientific research, the requirements of vacuum technology for its application pressure range are getting wider and wider. Most vacuum pumping systems need to be composed of several vacuum pumps to meet the requirements of the production and scientific research process.
Due to the wide range of working pressures involved in the vacuum application sector, it is impossible for any type of vacuum pump to be completely suitable for all working pressure ranges. For the convenience of use and the needs of various vacuum processes, various vacuum pumps are sometimes combined according to their performance requirements and applied in unit type.
Commonly used vacuum pumps include dry screw vacuum pumps, dry scroll vacuum pumps, water ring pumps, reciprocating pumps, slide valve pumps, rotary vane pumps, roots pumps, diffusion pumps, etc.
a. Ultimate pressure
With the vacuum pump connecting to the chamber and no gas being introduced, continuous pumping is carried out for a long time. When the gas pressure in the cavity no longer drops but maintains a certain value, this pressure is the ultimate pressure of the vacuum pump. The unit can be Pa or mbar
b. Pumping speed
The amount of gas flowing through the inlet of the vacuum pump per unit of time is the pumping speed. Its unit is L/s or m3/h
The pumping speed of the vacuum pump is related to the type of gas. Unless otherwise specified, the pumping speed refers to the pumping speed of the air.
c. Starting pressure
The starting pressure refers to the pressure at which the vacuum pump starts without damage and has a pumping effect, and its unit is Pa or mbar
d. Compressing ratio
Compression ratio refers to the ratio of the outlet pressure to the inlet pressure of the pump for a given gas
According to the working principle of vacuum pumps, vacuum pumps can be basically divided into two types, namely gas transmission pumps and gas capture pumps.
a. Gas transmission pump
The principle is to compress the gas from the inlet of the pump to the outlet and discharge it out of the pump, also known as a discharge-type vacuum pump. e.g. rotary mechanical vacuum pumps, steam jet pumps, and turbomolecular pumps.
b. Gas capture pump
The principle is to use various suction effects to adsorb the gas in the pump to achieve the purpose of reducing the pressure of the gas being pumped. e.g. ion pump, cryopump.
According to its performance characteristics and uses, it can be divided into the low vacuum pump, medium vacuum pump, high vacuum pump, and ultra-high vacuum pump.
a. Low vacuum pump: reciprocating vacuum pump, rotary vacuum pump, liquid ring vacuum pump, steam jet vacuum pump, and adsorption vacuum pump.
b. Medium vacuum pump: roots vacuum pump, multi-stage jet vacuum pump, multi-stage rotary mechanical vacuum pump, and high-speed rotary mechanical vacuum pump.
c. High vacuum pump: diffusion pumps and molecular pumps.
d. Ultra-high vacuum pump: ion pumps, cryopumps, etc.
|Types of pump||Pressure range (Pa)||Starting pressure (Pa)|
|Piston pump||1×105 ~ 1.3×102||1×105|
|Rotary vane pump||1×105 ~ 6.7×10-1||1×105|
|Water ring pump||1×105 ~ 2.7×103||1×105|
|Roots pump||1.3×103 ~ 1.3||1.3×103|
|Turbo molecular pump||1.3 ~ 1.3×10-5||1.3|
|Steam jet vacuum pump||1×105 ~ 1.3×10-1||1×105|
|Oil diffusion pump||1×10-2 ~ 1.3×10-7||1.3×10|
|Ion pump||1.3×10-3 ~ 1.3×10-9||6.7×10-1|
|Titanium pump||1.3×10-2 ~ 1.3×10-9||1.3×10-2|
|Cryogenic pump||1.3 ~ 1.3×10-11||1.3|
Application of vacuum pumps
Vacuum pumps are widely applied in machinery, metallurgy, chemical, medical, food, electronics, semiconductor, energy, high energy physics, aerospace, and other fields.