Vacuum pump structure and instructions for use

The vacuum pump is a rotary variable volume gas transfer pump. The vacuum pump must be equipped with a foreline pump before it can be used to have a large pumping speed within a wide pressure range. It is insensitive to dust and water vapor contained in the pumped gas. Widely used in metallurgy, chemical industry, food, electronic coating and other industries.

Vacuum pumps include dry screw vacuum pumps, water ring pumps, reciprocating pumps, slide valve pumps, rotary vane pumps, Roots pumps, and diffusion pumps. These pumps are indispensable for the application of vacuum processes in various industries of the national economy. . In recent years, along with the sustained and rapid development of China's economy, the vacuum pump-related downstream application industries have maintained a rapid growth momentum. At the same time, under the common pulling of vacuum pump application fields, China's vacuum pump industry has achieved sustained and stable development.

According to the 2013-2017 China Vacuum Pump Manufacturing Industry In-depth Research and Investment Forecast Analysis Report, the entry and success of foreign companies in China’s vacuum pump market has become an indisputable fact. Expansion, the United States Taishier Group, South Korea and other well-known international manufacturers have also looking for partners to build manufacturing base in China. Their appetite is huge and there is a potential for whale swallowing the vacuum pump market. In recent years, although some domestic companies have gradually emerged and have occupied a leading position in the vacuum pump market, most companies have poor R&D capabilities. Compared with foreign counterparts, high-end products are still at a disadvantage in terms of technology.

Features

(1) Larger pumping speeds over a wider pressure range;

(2) The rotor has a good geometrical symmetry, so the vibration is small and the operation is smooth. There is a gap between the rotor and between the rotor and the housing. Without lubrication, the friction loss is small, the driving power can be greatly reduced, and a higher rotation speed can be achieved;

(3) No oil sealing and lubrication inside the pump chamber can reduce the pollution of the vacuum system by oil vapor;

(4) There is no compression in the pump chamber and no exhaust valve. Simple and compact structure, insensitive to dust and water vapor in the exhausted gas;

(5) The compression is relatively low and the effect of hydrogen pumping is poor;

(6) The surface of the rotor is a curved cylindrical surface with complex shapes, making machining and inspection more difficult.

structure

(1) The overall structure of the pump

The layout of the pump body of the vacuum pump determines the overall structure of the pump.

The horizontal structure of the inlet and outlet openings of the vertical structure makes it easier to assemble and connect the piping. However, the center of gravity of the pump is high, and its stability is poor at high speeds, so this type is mostly used for small pumps.

The inlet of the horizontal pump is at the top and the exhaust port is at the bottom. Sometimes it is convenient to install and connect the vacuum system pipes. The exhaust ports can be taken out from the horizontal direction, that is, the inlet and exhaust directions are perpendicular to each other. At this time, the exhaust port can be opened in either left or right direction except for one end of the exhaust pipe, and the other end is blocked or connected to the bypass valve. This type of pump has a low center of gravity and good stability at high speeds. Generally large and medium-sized pumps use this structure.

The two rotor shafts of the pump are mounted perpendicular to the horizontal plane. This kind of structural assembly clearance is easy to control, the rotor assembly is convenient, and the pump has a small footprint. However, the higher the center of gravity of the pump and the inconvenience of disassembling the gear, the lubrication mechanism is also relatively complicated.

(2) Pump transmission method

The two rotors of the vacuum pump are relatively synchronously operated by a pair of high-precision gears. The drive shaft is coupled to the motor via a coupling. There are mainly two kinds of transmission structure layouts. One is that the motor and gear are placed on the same side of the rotor as shown in the figure. The 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 is not changed due to large torsional deformation of the drive shaft, so that the gap between the rotors is running. Uniform in the process. The biggest drawbacks of this transmission method are: a. There are three bearings on the drive shaft, which increases the difficulty of processing and assembly of the pump, and disassembly and adjustment of the gears are inconvenient; b. The overall structure is uneven, and the center of gravity of the pump is biased toward the motor and gears. Side of the box.

classification

According to its working principle is basically divided into two types of gas delivery pump and gas capture pump. Gas transfer pumps include: 1, liquid ring vacuum pump (water ring vacuum pump) 2, reciprocating vacuum pump 3, rotary vane vacuum pump 4, fixed-plate vacuum pump 5, spool valve vacuum pump 6, trochoidal vacuum pump 7, dry screw Vacuum pump 8, Roots vacuum pump 9, molecular vacuum pump 10, traction molecular pump 11, compound vacuum pump 12, water jet vacuum pump 13, gas jet pump 14, steam jet pump 15, diffusion pump, and the like. Gas capture pumps include: adsorption pumps, cryogenic pumps, etc.

Gas transmission pump

A gas transfer pump is a type of vacuum pump that can continuously inhale and discharge gas to achieve the purpose of pumping. There are basically two types of such pumps:

Variable capacity vacuum pump

A vacuum pump that uses the periodic variation of the pump chamber volume to complete the intake and exhaust processes. The gas is compressed before it is discharged. This pump is divided into two kinds of reciprocating and rotary type:

(1) Reciprocating vacuum pump: The reciprocating motion of the piston in the pump chamber is used to suck in, compress and discharge the gas. Therefore, it is also called a piston vacuum pump.

(2) Rotary vane vacuum pump: It uses the piston inside the pump chamber to do rotary motion to suck in gas, compress it and discharge it. The rotary vacuum pump has the following forms:

1 Oil-sealed vacuum pump: It is a rotary variable-capacity vacuum pump that uses oil to seal the gap between moving parts and reduce harmful space. This type of pump usually has a gas ballast, so it is also called a gas ballast pump. According to its structural characteristics are divided into the following five forms.

a rotary vane vacuum pump: the rotor is installed in the pump casing with a certain eccentricity and is close to the fixing surface of the inner surface of the pump casing. Two (or more than two) rotary vanes are installed in the rotor slot, and the rotary vane rotates when the rotor rotates. It is able to reciprocate along its radial groove and is always in contact with the inner wall of the pump casing. This rotor rotates with the rotor and divides the pump chamber into several variable volumes.

b.Spool 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 swingable slide valve guide, and the pump The cavity is divided into two variable volumes.

c. Fixed-plate vacuum pump: an eccentric rotor close to the inner surface of the pump is installed in the pump casing. The pump casing is equipped with a radial vane which is always in contact with the rotor surface. When the rotor rotates, the vane can slide up and down to pump The cavity is divided into two variable volumes.

d. Trochoidal vacuum pump: In the pump chamber eccentrically equipped with a trochoidal model rotor, it rotates along the inner wall of the pump chamber and divides the pump chamber into two variable volumes.

e. Multi-chamber rotary vane vacuum pump: A rotary vane vacuum pump with multiple independent working chambers driven by the same motor is installed in parallel in a pump casing.

2 Dry screw vacuum pump: It is a variable capacity vacuum pump that is not sealed with oil (or liquid).

3 Liquid ring vacuum pump: The rotor with multiple blades is eccentrically mounted in the pump casing. When it rotates, the liquid (usually water or oil) is thrown into the pump casing to form the concentric ring of the pump casing. The blades form several small volumes with periodic changes in volume, and are also known as rotary variable capacity vacuum pumps.

4 Roots vacuum pump: The pump is equipped with two rotors with double lobe or multi-lobal synchronous rotation in the opposite direction, and the rotor, rotor and the inner wall of the pump casing maintain a certain gap. It belongs to a rotary variable capacity vacuum pump. The mechanical booster pump is this type of vacuum pump.

Momentum transfer pumps: These pumps rely on high-speed rotating blades or high-speed jets to transfer momentum to gas or gas molecules, allowing gas to continuously transfer from the pump's inlet to the outlet. Specific can be divided into the following types.

(1) Molecular vacuum pump: It is a kind of vacuum pump that uses high-speed rotating rotor to transfer energy to gas molecules to make it compressed and exhausted. It has the following types:

1 Traction molecular pump: Gas molecules collide with a high-speed rotor to gain power and are sent to the exit. Therefore, it is a momentum transfer pump.

2 turbo-molecular pump: The pump is equipped with a slotted disc or a bladed rotor that rotates between the stator discs (or stators). The line speed of the rotor circumference is high. This kind of pump usually works in the molecular flow state.

3 Compound molecular pump: It is a compound molecular vacuum pump that is connected in series by turbo-type and traction type molecular pumps.

(2) Jet vacuum pump: It is a kind of momentum transfer pump that uses the high pressure jet produced by the VENTURI effect to deliver gas to the outlet. It is suitable for working in the state of sticking and transient flow. This pump can be further divided into the following categories:

1 Liquid jet vacuum pump: Jet vacuum pump with liquid (usually water) as the working medium.

2 Gas jet vacuum pump: Jet vacuum pump with non-condensable gas as working medium.

3 Steam jet vacuum pump: Hungry jet vacuum pump using steam (water, oil or mercury vapor) as working medium

(3) Diffusion pump: A jet vacuum pump that uses a low-pressure, high-speed steam stream (steam, such as oil or mercury) as a working medium. Gas molecules diffuse into the steam jet and are sent to the exit. The density of gas molecules in the jet is always low, and the pump is suitable for working in the molecular flow state. It can be divided into:

1 Self-purifying diffusion pump: an oil diffusion pump with volatile impurities in the pump fluid being transported to the outlet by a special machine without returning to the boiler

2 Fractionation Diffusion Pump: This pump has a fractionation device, so that the steam pressure of the working fluid with low steam pressure enters the nozzle for high vacuum working, and the steam with high steam pressure enters into the nozzle for low vacuum work, it is a kind of Oil diffusion pump.

(4) Diffusion jet pump: It is a kind of momentum transfer pump that is composed of a single-stage or multi-stage nozzle with the characteristics of a diffusion pump and a single-stage or multi-stage nozzle with the characteristics of a jet vacuum pump. The oil booster pump is in this form.

(5) Ion transport pump: It is a kind of momentum transfer pump that transfers ionized gas to the outlet under the action of electromagnetic or electric fields.

Gas capture pump

The pump is a type of vacuum pump in which gas molecules are adsorbed or condensed on the inner surface of the pump, thereby reducing the number of gas molecules in the container and achieving the purpose of pumping. The pump has the following types.

Adsorption pump: A trap type vacuum pump mainly relying on the physical adsorption of a large surface adsorbent (such as a porous material) to pump gas.

Getter pump: It is a vacuum pump that uses a getter to chemically capture gas. Getters are usually metals or alloys in the form of blocks or deposited fresh films. Sublimation pumps belong to this form.

Getter ion pump: It is to make the ionized gas adsorb on the surface of the getter material through the action of electromagnetic field or electric field, so as to achieve the purpose of pumping gas. It has the following types.

(1) Evaporation ion pump: A vacuum pump in which the ionized gas in the pump is adsorbed on a getter material that sublimates (or vaporizes) in a discontinuous or continuous manner and covers the inner wall of the pump to achieve pumping.

(2) Sputter ion pump: A vacuum pump in which the ionized gas in the pump is adsorbed on the getter material that is sputtered from the cathode continuously to achieve the purpose of pumping.

Cryopump: A vacuum pump that uses a cryogenic surface to trap gas

According to its degree of vacuum can be divided into: rough vacuum, high vacuum, ultra-high vacuum three categories.

Rough vacuum system

Mainly used to extract air and other gases that are somewhat corrosive, insoluble in water, and allow a small amount of solid particles. Widely used in food, textile, pharmaceutical, chemical and other industries vacuum evaporation, concentration, impregnation, drying and other processes. The pump has the advantages of high vacuum, simple structure, convenient use, reliable operation and convenient maintenance.

Mainly used for rough vacuum. In the process of pumping a large amount of gas. It is mainly used to extract air and other non-corrosive, insoluble water, gas containing a small amount of solid particles in order to form a vacuum in a closed container. A small amount of liquid is allowed in the sucked gas. It is widely used in machinery, pharmaceuticals, food, petrochemical and other industries.

It is one of the major vacuum equipments for obtaining rough vacuum. Widely used in chemical, food, building materials and other departments, especially in vacuum crystallization, drying, filtration, evaporation and other processes are more appropriate.

The oil-free (anti-corrosion) vertical reciprocating vacuum pump is the replacement product of the horizontal vacuum pump and is the main equipment for obtaining rough vacuum. Thanks to the fully sealed device, complete isolation of the crankcase and the cylinder is achieved; in addition to the use of self-lubricating material for the piston rings, advanced oil-free lubrication is achieved. Because there is no sewage discharge, this type of vacuum pump is particularly suitable for vacuum distillation, vacuum evaporation, vacuum drying, vacuum concentration, vacuum impregnation and other processes in the chemical, pharmaceutical and food industries.

High vacuum system

Spool type vacuum pump

(Rotary Piston Vacuum Pump)

Widely used in vacuum crystal pulling, vacuum coating, vacuum metallurgy, vacuum heat treatment, vacuum impregnation, vacuum drying, vacuum distillation, vacuum clay, aerospace simulation test and other new materials, new technologies, new processes in the production and development.

The slide valve vacuum pump can be used alone, or it can also be used as a fore pump of Roots vacuum pump, oil booster pump, and oil diffusion pump. When the suction is corrosive to ferrous metals, chemical reactions to vacuum oils, gases containing large amounts of steam, and large amounts of dust, additional equipment is required. Advantages: Compared to the rotary vane vacuum pump, the durability is several times higher and the pumping rate is high, and the price is relatively high.

One of the basic equipment used to extract gas from a closed container. It can be used alone or as a foreline pump for booster pumps, diffusion pumps, and molecular pumps. The pump is widely used in metallurgy, machinery, electronics, chemical, petroleum, pharmaceutical and other industries in vacuum smelting, vacuum coating, vacuum heat treatment, vacuum drying and other processes.

Rotary vacuum pump

(Sliding Vane Rotary Vacuum Pump)

Has the advantages of compact structure, small size, light weight, low noise, low vibration and so on. Therefore, it is suitable for use as a fore pump of a diffusion pump, and is more suitable for precision instrument matching and laboratory use. For example: mass spectrometry instruments, refrigerator lines, vacuum freeze dryers, etc.

Roots vacuum pump

(Roots Vacuum Pump)

It is a rotary variable-capacity vacuum pump. It must be equipped with a foreline pump before it can be used in a wide range of pressures. It has a large pumping speed and is insensitive to dust and water vapor contained in the pumped gas. Widely used in metallurgy, chemical industry, food, electronic coating and other industries. It is mainly used for the main pump of the vacuum unit and needs to be assisted by the fore pump. Such as: water ring vacuum pump, slide valve vacuum pump, vertical oil-free vacuum pump, molecular vacuum pump and so on. The largest Roots vacuum pump maintains a record of 10,000 L/S.

More vacuum pump information is available at China Vacuum Pump Trading Network (/).