Gas transmission vacuum pump types

According to the working principle of vacuum pump, vacuum pump can be basically divided into two types, namely gas transmission pump and gas trapping pump.

However, with the application of vacuum technology in the field of production and scientific research, the requirement of its application pressure range becomes wider and wider. Most of them need several vacuum pumps to form a vacuum pumping system to suck together before they can meet the requirements of production and scientific research. Therefore, vacuum units composed of different types of vacuum pumps are selected for suction. There are many cases. Here is a brief introduction of some kinds of gas transmission vacuum pumps.

Gas transfer pump is a kind of vacuum pump which can continuously inhale and exhaust gas to achieve the purpose of pumping. There are basically two types of pumps:

The first type is the variable volume vacuum pump: the variable volume vacuum pump is a kind of vacuum pump which uses the periodic change of the volume of the pump chamber to complete the process of suction and exhaust. The gas is compressed before it is discharged. This kind of pump can be divided into reciprocating type and rotary type.

(1)Reciprocating vacuum pump: The piston in the pump chamber is used for reciprocating motion, and the gas is inhaled, compressed and discharged. Therefore, it is also called piston vacuum pump (diaphragm vacuum pump is also a reciprocating vacuum pump).

(2) Rotary vacuum pump: It uses the rotor in the pump chamber to rotate, inhale, compress and discharge the gas. There are several types of rotary vacuum pumps as follows:

Oil-sealed vacuum pump: It is a kind of rotary varactor vacuum pump that uses oil to seal the clearance between moving parts and reduce harmful space. This kind of pump usually has air-ballast device, so it is also called air-ballast vacuum pump. According to its structural characteristics, it can be divided into the following five types:

(A) Rotary vane vacuum pump: The rotor is installed in the pump housing with a certain eccentricity and close to the fixed surface of the inner surface of the pump housing. There are two (or more) rotating vanes in the rotor groove. When the rotor rotates, the rotating vane can slide back and forth along its radial groove and keep in contact with the inner wall of the pump housing. The rotating vane rotates with the rotor, and the pump cavity can be divided into two parts. Several variable volumes.

(B) Sliding valve vacuum pump: a sliding valve is installed outside the eccentric rotor. The rotor rotates to drive the sliding valve to slide and roll along the inner wall of the pump housing. The sliding valve stem on the upper part of the sliding valve can slide in the swinging sliding valve guide rail, and the pump chamber is divided into two variable volumes.

(C) Multi-chamber rotary vane vacuum pump: A rotary vane vacuum pump with multiple independent chambers driven by the same motor is mounted in parallel in a pump housing.

Liquid ring vacuum pump

(3) Liquid ring vacuum pump: The rotor with multi-blades is eccentrically installed in the pump shell. When it rotates, the liquid (usually water or oil) is thrown into the pump shell to form a concentric liquid ring. The liquid ring and the rotor blade form several small volumes with periodic changes in volume. When the medium is water, it is also called

(4) Roots vacuum pump: There are two double or multi-blade rotors rotating in opposite direction synchronously in the pump, and there are certain clearances between the rotors and the inner wall of the pump shell. It belongs to the rotary varactor vacuum pump. Mechanical booster pump is this type of vacuum pump.

(5) Screw Vacuum Pump: A pair of screw is used as a suction and exhaust equipment for synchronous high-speed reverse rotation in the pump housing. It is a renewal product of oil-sealed vacuum pump, which can extract gas containing a large amount of water vapor and a small amount of dust. It has been widely used in major pharmaceutical and chemical enterprises in China.

Claw vacuum pump: The principle of claw vacuum pump is similar to Roots. It uses two claw rotors and pump chamber to form pumping volume. The rotors can be opened and closed automatically during rotation.

Vortex vacuum pump: Vortex vacuum pump is an oil-free vacuum pump evolved from scroll compressor.

Screw vacuum pump, claw vacuum pump and scroll vacuum pump can also be called dry vacuum pump, which can realize no oil seal.

The second type is momentum transfer pump. This pump relies on high-speed rotating blades or high-speed jet to transfer momentum to gas or gas molecules, so that gas is continuously transmitted from the pump’s inlet to the outlet. It can be divided into the following types:

Molecular vacuum pump

(1) Molecular vacuum pump: It is a kind of vacuum pump that uses the high-speed rotating rotor to transmit energy to the gas molecule and make it compress and exhaust.

The second type is momentum transfer pump. This pump relies on high-speed rotating blades or high-speed jet to transfer momentum to gas or gas molecules, so that gas is continuously transmitted from the pump’s inlet to the outlet. It can be divided into the following types:

(A) Molecular vacuum pump: It is a kind of vacuum pump that uses the high-speed rotating rotor to transmit energy to the gas molecule and make it compress and exhaust. It has the following types:

(B) Traction Molecular Pump: Gas molecule collides with a high-speed rotor to obtain momentum, which is sent to the exit. Therefore, it is a momentum transfer pump.

(C) Turbomolecular pump: The pump is equipped with a grooved disc or a rotor with blades, which rotates between stator discs (or stator plates). The linear velocity around the rotor is very high. This kind of pump usually works in the state of molecular flow.

(D) Compound molecular pump: It is a kind of compound molecular vacuum pump which is composed of turbine and traction molecular pumps in series.

(2) Jet Vacuum Pump: It is a momentum transfer pump that uses the high-speed jet generated by Venturi pressure drop to transport gas to the outlet. It is suitable for working in viscous and transitional flow conditions. This kind of pump can be divided into the following kinds in detail:

(A) Liquid jet vacuum pump: jet vacuum pump with liquid (usually water) as working medium.

(B) Gas jet vacuum pump: jet vacuum pump with non-condensable gas as working medium.

(C) Steam jet vacuum pump: a jet vacuum pump with steam (water, oil or mercury vapor) as working medium.

oil diffusion pump

(3) Diffusion pump: jet vacuum pump with low pressure and high speed steam flow (such as oil or mercury vapor) as working medium. Gas molecules diffuse into a vapor jet and are sent to the exit. The gas molecular density in the jet is always very low, and this pump is suitable for working in the molecular flow state. Can be divided into:

(A) Self-purification diffusion pump: An oil diffusion pump in which volatile impurities in the pump fluid are conveyed to the outlet by special machinery without returning to the boiler.

(B) Fractional Diffusion Pump: This kind of pump has a fractionation device, which makes the working liquid vapor with low vapor pressure enter the nozzle of high vacuum operation, and the working liquid vapor with high vapor pressure enter the nozzle of low vacuum operation. It is a multistage oil diffusion pump.

(4) Diffusion jet pump: It is a momentum transfer pump consisting of a single or multi-stage nozzle with the characteristics of diffusion pump and a single or multi-stage nozzle with the characteristics of jet vacuum pump. Oil booster pump belongs to this type.