Vacuum pump is a device that produces, improves and maintains vacuum in a closed space by various means. Vacuum pump can be defined as: mechanical, physical, chemical or physicochemical methods to be pumped by the container to obtain a vacuum device or equipment. With the development of vacuum applications, a variety of vacuum pumps have been developed, with pumping speeds ranging from a few liters per second to hundreds of thousands or millions of liters per second. Limit pressure (extreme vacuum) from coarse vacuum to over 10-12 Pa high vacuum range.
Because of the wide range of working pressure involved in the vacuum application department, any type of vacuum pump can not be fully applicable to all the working pressure range, only according to different working pressure range and different working requirements, the use of different types of vacuum pump. In order to use conveniently and meet the needs of various vacuum processes, various vacuum pumps are sometimes combined according to their performance requirements for unit type applications.
Any pump that uses mechanical movement (rotation or sliding) to obtain vacuum is called mechanical vacuum pump. According to its working principle and structural characteristics, the mechanical vacuum pump is described as follows:
It is a vacuum pump which uses the periodic change of the volume of the pump chamber to complete suction and exhaust to achieve the purpose of pumping gas. The gas is compressed before discharging the pump chamber. This pump is divided into two types: reciprocating and rotary.
(1) reciprocating vacuum pump
Using the reciprocating motion of the piston in the pump chamber, the gas is sucked, compressed and discharged. Also known as piston vacuum pump.
The rotation of the rotor parts of the pump chamber causes the gas to breathe, compress and discharge. It has roughly the following categories:
<1>, oil sealed vacuum pump
It is a rotary variable capacity vacuum pump which uses the clearance between the moving parts of the vacuum pump oil seal to reduce the harmful space in the pump. Such pumps are usually equipped with pneumatic devices. It mainly includes rotary vane vacuum pump, fixed vane vacuum pump, slide valve vacuum pump, residual cycloid vacuum pump and so on.
<2>, liquid ring vacuum pump
The rotor with multiple blades is eccentrically mounted in the pump housing. When it rotates, the working fluid is thrown into the pump shell to form a liquid ring concentric with the pump shell, and the liquid ring with the rotor blade forms several small rotating variable volume suction and exhaust cavities with periodic volume changes. The working fluid is usually water or oil, so it is also called water ring vacuum pump or oil ring vacuum pump.
<3>, dry vacuum pump
It is a variable volume vacuum pump sealed inside the pump without oil (or liquid). Because the dry vacuum pump chamber does not need working fluid, therefore, suitable for semiconductor industry, chemical industry, pharmaceutical industry and food industry, such as the need for oil-free clean vacuum environment process occasions.
<4>, roots vacuum pump
The pump is equipped with two double leaf or multi leaf rotors which rotate synchronously in opposite directions. The clearance between the rotor and the rotor and the inner wall of the pump shell is maintained.
It relies on high-speed rotating blades or high-speed jet to transfer momentum to gas or gas molecules, so that gas continuously from the pump inlet to the outlet. Such pumps can be divided into the following forms:
It is a vacuum pump that transfers momentum to the gas molecule by a high-speed rotating rotor to obtain the directional velocity, which is compressed and driven to the exhaust port for the front stage pumping. This pump can be divided into:
<1>, traction molecular pump
Gas molecules collide with the rotor at high speed, and momentum is driven to the outlet of the pump.
<2>, turbo molecular pump
High speed rotating blades and stationary vane cooperate to realize the exhaust. Such pumps usually work in molecular flow.
<3>, composite molecular pump
It is a kind of compound molecular vacuum pump which is composed of two kinds of molecular pumps, turbine and traction.
Mechanical vacuum pump is the most common type of pump used in the field of vacuum application, it is an important part of vacuum acquisition equipment.