Structure and operation instructions of vacuum pump

The vacuum pump is a kind of rotary variable volume gas delivery pump The vacuum pump must be equipped with a front stage pump to be used in a wide pressure range with a large pumping speed It is not sensitive to the dust and water vapor contained in the extracted gas It is widely used in metallurgy, chemical industry, food, electronic coating and other industries The development of vacuum pump includes dry screw vacuum pump, water ring pump, reciprocating pump, slide valve pump, rotary vane pump, roots pump and diffusion pump These pumps are essential main pumps in the application of vacuum technology in various industries of national economy In recent years, with the sustained and high-speed development of China's economy, the downstream application industry related to vacuum pump has maintained a rapid growth momentum At the same time, driven by the continuous expansion of the application field of vacuum pump and other factors, China's vacuum pump industry has achieved sustained and stable development In China's vacuum pump market, the entry and success of foreign enterprises has become an indisputable fact Japan's vacuum stations are distributed everywhere, Germany's LeiBao is expanded in China, and international manufacturers such as American tassel group and South Korea Youcheng are looking for partners to build manufacturing bases in China They have a big appetite, and they are in the market for vacuum pumps In recent years, although some domestic enterprises have gradually risen up and occupied a relatively first position in the vacuum pump market, most of them have poor R & D capabilities, and compared with their foreign counterparts, their products are still at a disadvantage in technology Features: (1) large pumping speed in a wide pressure range; (2) the rotor has good geometric symmetry, so the vibration is small and the operation is stable There is clearance between rotors and between rotors and shells, no lubrication, small friction loss, which can greatly reduce the driving power, so as to achieve higher speed; (3) no oil sealing and lubrication in the pump cavity, which can reduce the pollution of oil vapor to the vacuum system; (4) no compression in the pump cavity, no exhaust valve The structure is simple and compact, not sensitive to dust and water vapor in the extracted gas; (5) the compression ratio is low, and the effect of hydrogen extraction is poor; (6) the rotor surface is a curve cylinder with complex shape, so it is difficult to process and check Structure (1) the overall structure of the pump The layout of the vacuum pump determines the overall structure of the pump The vertical structure has horizontal inlet and outlet, and it is convenient to assemble and connect pipelines But the center of gravity of the pump is high, and its stability is poor at high speed, so this type of pump is mostly used for small pump The air inlet of the horizontal pump is on the top and the air outlet is on the bottom Sometimes, in order to facilitate the installation and connection of vacuum system pipes, the exhaust port can be connected from the horizontal direction, that is, the inlet and exhaust directions are mutually perpendicular At this time, the exhaust port can be opened from the left or right direction In addition to connecting one end of the exhaust pipe, the other end is blocked or connected with the bypass valve The pump has low center of gravity and good stability at high speed Generally, large and medium-sized pumps use this structure The two rotor shafts of the pump are installed vertically with the horizontal plane The assembly clearance of the structure is easy to control, the rotor is easy to assemble and the pump occupies a small area However, the center of gravity of the pump is high and the gear is inconvenient to be disassembled, and the lubricating mechanism is relatively complex (2) the transmission mode of the pump: the two rotors of the vacuum pump realize their relative synchronous operation through a pair of high-precision gears The driving shaft is connected with the motor through the coupling There are mainly two types of transmission structure arrangement: one is that the motor and gear are placed on the same side of the rotor as shown in the figure Driven rotor is directly driven by the motor end gear, so that the torsional deformation of the active rotor shaft is small, the gap between the two rotors will not be changed due to the large torsional deformation of the active shaft, so that the gap between the rotors is even in the operation process The main disadvantages of this drive mode are: A There are three bearings on the driving shaft, which increases the difficulty of processing and assembly of the pump, and the disassembly and adjustment of the gear is also inconvenient; B the overall structure is uneven, and the center of gravity of the pump is inclined to the side of the motor and gearbox According to its working principle, it can be divided into two types: gas delivery pump and gas capture pump Gas delivery pump includes: 1 Liquid ring vacuum pump (water ring vacuum pump) 2 Reciprocating vacuum pump 3 Rotary vane vacuum pump 4 Fixed vane vacuum pump 5 Slide valve vacuum pump 6 Cycloid vacuum pump 7 Dry screw vacuum pump 8 Roots vacuum pump 9 Molecular vacuum pump 10 Traction sub pump 11 Composite vacuum pump 12 Water jet vacuum pump 13 Gas jet pump 14 Steam jet pump 15 Diffusion pump, etc Gas capture pump includes: adsorption pump, low temperature pump and other gas transfer pump It is a kind of vacuum pump that can continuously suction and discharge gas to achieve the purpose of pumping There are basically two types of this pump: variable volume vacuum pump It is a vacuum pump that uses the periodic change of pump cavity volume to complete the suction and exhaust process, and the gas is compressed before discharging This kind of pump is divided into reciprocating and rotary vane two kinds: (1) reciprocating vacuum pump: it uses the piston in the pump cavity to do reciprocating motion, to suction, compress and discharge the gas Therefore, it is also called piston vacuum pump (2) rotary vane vacuum pump: it uses the piston in the cavity of the pump to do rotary movement, to suction, compress and discharge the gas Rotary vacuum pump has the following forms: ① oil sealed vacuum pump: it is a rotary variable volume vacuum pump which uses oil to seal the gap between moving parts and reduce harmful space This kind of pump is usually equipped with 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 forms A rotary vane vacuum pump: the rotor is installed in the pump shell with a certain eccentricity and close to the fixed surface of the inner surface of the pump shell Two (or more) rotary discs are installed in the rotor groove When the rotor rotates, the rotary disc can slide back and forth along its radial groove and contact with the inner wall of the pump shell all the time The rotary disc rotates with the rotor, which can divide the pump cavity into several variable volumes B slide valve type vacuum pump: a slide valve is installed outside the eccentric rotor The rotation of the rotor drives the slide valve to slide and roll along the inner wall of the pump housing The slide valve rod on the upper part of the slide valve can slide in the swinging slide valve guide rail, and the pump cavity is divided into two variable volumes C fixed vane type vacuum pump: an eccentric rotor close to the internal surface of the pump is installed in the pump housing, and a radial sliding vane which always contacts the surface of the rotor is installed on the pump housing When the rotor rotates, the sliding vane can slide up and down to divide the pump cavity into two variable volumes D cycloid vacuum pump: a cycloid shaped rotor is eccentrically installed in the pump cavity, which rotates along the inner wall of the pump cavity and divides the pump cavity into two variable volumes E multi chamber rotary vane vacuum pump: a rotary vane vacuum pump with multiple independent chambers driven by the same motor is installed in parallel in a pump housing ② dry screw vacuum pump: it is a variable volume vacuum pump without oil (or liquid) sealing ③ liquid ring vacuum pump: the rotor with multiple blades is installed in the pump casing eccentrically When it rotates, the liquid (usually water or oil) is thrown into the pump casing to form a concentric ring liquid of the pump casing The ring liquid and the rotor blades form several small volumes with periodic volume changes, so it is also called rotary variable volume vacuum pump ④ roots vacuum pump: the pump is equipped with two double blade or multi blade rotors rotating synchronously in opposite directions, and there is a certain gap between the rotors and between the rotors and the inner wall of the pump housing It belongs to rotary variable volume vacuum pump The mechanical booster pump is this kind of vacuum pump Momentum transfer pump: this kind of pump relies on high-speed rotating blades or high-speed jets to transfer momentum to gas or gas molecules, so that the gas is continuously transferred from the pump inlet to the outlet It can be divided into the following types (1) molecular vacuum pump: it is a vacuum pump that uses a high-speed rotating rotor to transmit energy to the gas molecules to compress and exhaust them It has the following types: ① traction molecular pump: the gas molecules collide with the rotor of high-speed movement to obtain the force, which is sent to the outlet, so it is a momentum transfer pump ② turbine molecular pump: the pump is equipped with a disk with grooves or a rotor with blades, which rotates between the stator disks (or fins) The linear speed of the rotor circumference is very high This kind of pump usually works in the molecular flow state ③ compound molecular pump: it is a kind of compound molecular vacuum pump which is connected in series by two kinds of molecular pumps: turbo type and traction type (2) jet vacuum pump: it is a kind of momentum transfer pump that uses the high-speed jet produced by the pressure drop of Venturi effect to deliver gas to the outlet It is suitable for working in the state of viscous retention and transition flow This kind of pump can be further divided into the following categories: ① liquid jet vacuum pump: jet vacuum pump with liquid (usually water) as working medium ② Gas jet vacuum pump: a jet vacuum pump with non condensable gas as working medium ③ steam jet vacuum pump: vacuum pump (3) diffusion pump with steam (water, oil or mercury vapor) as working medium: vacuum pump with low-pressure and high-speed steam flow (oil or mercury vapor) as working medium Gas molecules diffuse into the steam jet and are sent to the outlet The molecular density of the gas in the jet is always very low This kind of pump is suitable for working in the molecular flow state It can be divided into: ① self purification diffusion pump: a kind of oil diffusion pump in which the volatile impurities in the pump liquid are transported to the outlet by special machinery without returning to the boiler ② Fractionation diffusion pump: this pump has a fractionation device, which enables the working liquid steam with low steam pressure to enter the nozzle with high vacuum operation, while the working liquid steam with high steam pressure to enter the nozzle with low vacuum operation It is a multi-stage oil diffusion pump (4) diffusion jet pump: it is a momentum transfer pump composed of a single-stage or multi-stage nozzle with diffusion pump characteristics and a single-stage or multi-stage nozzle with injection vacuum pump characteristics in series The oil booster pump belongs to this type (5) ion transfer pump: it is a kind of momentum transfer pump that delivers the ionized gas to the outlet under the action of electromagnetic field or electric field Gas trapping pump this kind of pump is a kind of vacuum pump in which gas molecules are adsorbed or condensed on the inner surface of the pump, so as to reduce the number of gas molecules in the container and achieve the purpose of pumping There are several types of pumps Adsorption pump: it mainly relies on the physical adsorption of adsorbents with large surface (such as porous materials) to pump air It is a kind of vacuum pump that uses getter to capture gas by chemical combination Getters are usually metals or alloys in the form of lumps or deposited fresh films Sublimation pump belongs to this form Getter ion pump: it is used to make the ionized gas adsorb on the surface of the material with getter through the action of electromagnetic field or electric field, so as to achieve the purpose of getter It has the following types (1) evaporation ion pump: a vacuum pump in which the ionized gas in the pump is adsorbed on the suction material which is sublimed (or evaporated) in an intermittent or continuous way and covered on the inner wall of the pump to realize the pumping (2) sputter ion pump: a vacuum pump in which the ionized gas in the pump is adsorbed on the suction material continuously sputtered from the cathode to achieve the purpose of pumping Low temperature pump: vacuum pump that uses low temperature surface to catch gas can be divided into three categories according to its vacuum degree: coarse vacuum, high vacuum and ultra-high vacuum The coarse vacuum system is mainly used to remove air