Classification of vacuum pumps

According to the working principle of vacuum pumps, they can be basically divided into two types, namely gas capture pumps and gas transfer pumps. It is widely used in industries such as metallurgy, chemical, food, and electronic coating.

Common 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 essential main pump types in the application of vacuum technology in various industries of China's national economy.

Gas transfer pump

Gas transfer pump is a vacuum pump that can continuously suck in and discharge gas to achieve the purpose of pumping. There are basically two types of pumps:

Variable capacity vacuum pump

A vacuum pump that utilizes the periodic variation of pump chamber volume to complete the suction and exhaust processes, where gas is compressed before being discharged. This type of pump is divided into reciprocating and rotary types:

(1) Reciprocating vacuum pump: It utilizes the reciprocating motion of the piston inside the pump chamber to suck in, compress, and discharge gas. Therefore, it is also known as a piston vacuum pump.

(2) Rotary vane vacuum pump: It uses the piston in the pump chamber to rotate, suck in, compress, and discharge gas. There are several forms of rotary vacuum pumps:

① Oil sealed vacuum pump: It is a rotary variable volume vacuum pump that uses oil to seal the gaps between moving parts and reduce harmful space. This type of pump usually comes with a gas ballast device, so it is also known as a gas ballast vacuum pump. 

② Dry screw vacuum pump: It is a variable volume vacuum pump that does not require oil (or liquid) sealing.

③ Liquid ring vacuum pump: A rotor with multiple blades is eccentrically installed inside the pump casing. When it rotates, it throws liquid (usually water or oil) into the pump casing to form a concentric ring liquid. The ring liquid and the rotor blades form several small volumes with periodic volume changes, so it is also known as a rotary variable volume vacuum pump.

④ Roots vacuum pump: The pump is equipped with two double bladed or multi bladed rotors that rotate synchronously in opposite directions, and a certain gap is maintained between the rotors and between the rotors and the inner wall of the pump casing. It belongs to the rotary variable volume vacuum pump. A mechanical booster pump is a form of vacuum pump.

Momentum transfer pump: This type of pump relies on high-speed rotating blades or high-speed jets to transfer momentum to gas or gas molecules, continuously transferring gas from the pump's inlet to the outlet. It can be specifically divided into the following types.

(1) Molecular vacuum pump: It is a vacuum pump that uses a high-speed rotating rotor to transfer energy to gas molecules, compressing and exhausting them. It has the following types:

① Traction molecular pump: Gas molecules collide with a high-speed rotor to obtain force, which is then sent to the outlet. Therefore, it is a momentum transfer pump.

② Turbomolecular pump: The pump is equipped with slotted disks or bladed rotors that rotate between stator disks (or vanes). The linear velocity of the rotor circumference is very high. This type of pump typically operates in a molecular flow state.

③ Composite molecular pump: It is a composite molecular vacuum pump composed of two types of molecular pumps, turbine type and traction type, connected in series.

(2) Jet vacuum pump: It is a momentum transfer pump that utilizes the pressure drop of the Venturi effect to produce a high-speed jet that delivers gas to the outlet, suitable for working in viscous and transitional flow states. 

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

(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 jet vacuum pump characteristics connected in series. The oil booster pump belongs to this form.

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

Gas capture pump

This type of pump is a 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. There are several types of pumps.

Adsorption pump: It mainly relies on the physical adsorption of adsorbents with large surfaces (such as porous materials) to extract air, and is a type of trapping vacuum pump.

Suction pump: It is a vacuum pump that uses suction agents to chemically bind and capture gases. Absorbents are usually metals or alloys that exist in the form of blocks or deposited fresh films. Sublimation pumps belong to this form.

Absorbent ion pump: It is a device that allows ionized gas to be adsorbed onto a surface with an absorbent material through the action of an electromagnetic or electric field, in order to achieve the purpose of pumping.

According to its vacuum degree, it can be divided into three categories: coarse vacuum, high vacuum, and ultra-high vacuum.

Coarse vacuum system

1. It is mainly used to extract air and other gases that are corrosive, insoluble in water, and allowed to contain a small amount of solid particles. Widely used in vacuum evaporation, concentration, impregnation, drying and other processes in industries such as food, textile, pharmaceutical, and chemical. This type of pump has the characteristics of high vacuum degree, simple structure, easy use, reliable operation, and easy maintenance.

2. Mainly used for rough vacuum. In the process of extracting large amounts of air. It is mainly used to extract air and other gases that are non corrosive, insoluble in water, and contain a small amount of solid particles, in order to create a vacuum in a closed container. A small amount of liquid is allowed to mix in the absorbed gas. It is widely used in industries such as machinery, pharmaceuticals, food, petrochemicals, etc.

3. It is one of the main vacuum equipment for obtaining rough vacuum. Widely used in chemical, food, building materials and other sectors, especially suitable for processes such as vacuum crystallization, drying, filtration, evaporation, etc.

Oil free (corrosion-resistant) vertical reciprocating vacuum pump is an upgraded product of horizontal vacuum pump and is the main equipment for obtaining rough vacuum. Due to the use of a fully sealed device, complete isolation between the crankcase and cylinder has been achieved; By adding self-lubricating materials to the piston rings, advanced oil-free lubrication and A43 lubrication are achieved. Due to the absence of wastewater discharge, this type of vacuum pump is particularly suitable for processes such as vacuum distillation, vacuum evaporation, vacuum drying, vacuum concentration, and vacuum impregnation in industries such as chemical, pharmaceutical, and food.

High vacuum system

Slide  valve vacuum pump

Widely used in the production and development of new materials, technologies, and processes such as vacuum crystal pulling, vacuum coating, vacuum metallurgy, vacuum heat treatment, vacuum impregnation, vacuum drying, vacuum distillation, vacuum mud refining, aerospace simulation testing, etc.

The slide valve vacuum pump can be used alone or as a pre pump for Roots vacuum pumps, oil booster pumps, and oil diffusion pumps. When extracting gases that corrode ferrous metals, react chemically with vacuum oil, contain a large amount of steam, and have a large amount of dust, additional devices are required. Advantages: Compared to rotary vane vacuum pumps, it has several times higher durability and faster pumping rate, and is relatively more expensive.

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

Rotary vane vacuum pump

It has the advantages of compact structure, small volume, light weight, low noise, and low vibration. So, it is suitable as a front-end pump for diffusion pumps, and more suitable for precision instrument matching and laboratory use. For example: mass spectrometer, refrigerator assembly line, vacuum freeze dryer, etc.

Roots vacuum pump

It is a rotary variable volume vacuum pump that requires a front-end pump to be used in a wide pressure range, has a high pumping speed, and is insensitive to dust and water vapor in the extracted gas. Widely used in industries such as metallurgy, chemical, food, and electronic coating. Mainly used as the main pump for vacuum units, it requires the assistance of a front-end pump. For example: water ring vacuum pump, slide valve vacuum pump, vertical oil-free vacuum pump, molecular vacuum pump, etc. The largest Roots vacuum pump in China holds a record of 20000L/S.