Vacuum pump is a kind of vacuum equipment, which can be used to extract and improve the vacuum environment by physical, chemical or mechanical methods. There are many types of vacuum pumps, which have been applied in many industrial fields in China. This paper mainly introduces the classification of vacuum pumps and the performance, advantages and disadvantages of several common vacuum pumps, and analyzes the development trend of vacuum pumps in China
1、 The meaning of vacuum
In the 17th century, Italian physicist Torricelli revealed the existence of “vacuum”. Vacuum refers to the gas state where the gas pressure is lower than one atmospheric pressure in a given space. The state where there is no gas at all is called absolute vacuum. Generally speaking, vacuum refers to relative vacuum, that is, under the lowest pressure that can be reached, there are still a few gas molecules in each cubic meter of gas. In vacuum technology, “vacuum degree” and “pressure” are generally used to express the degree of vacuum. The lower the pressure in a certain space, the higher the vacuum degree, and the higher the pressure, the lower the vacuum degree. According to the different physical characteristics of each pressure range, the vacuum is generally divided into rough vacuum, low vacuum, high vacuum and ultra-high vacuum
2、 Classification of vacuum pumps
Since the beginning of the 20th century, the vacuum technology has been developing continuously, and the types of vacuum equipment are more and more, and the application fields are also gradually expanding. According to the working principle of vacuum pump, it can be divided into two basic types: gas transfer pump and gas trap pump. Gas transfer pump is mainly through the continuous suction and discharge of gas to achieve the purpose of pumping, gas capture pump through the 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.
3、 Several common vacuum pumps in industrial field and their development trend
1. Water ring vacuum pump is a kind of variable volume pump, which can extract flammable, explosive and corrosive gases, as well as gas containing dust and moisture. This kind of vacuum pump has the advantages of simple structure, easy maintenance, small wear and tear, high safety and no pollution of the gas to be transported. The disadvantage is that the efficiency is not high and the vacuum degree is not high (coarse vacuum). The main raw material of water ring pump is casting, which is easy to process and belongs to labor-intensive product. Therefore, compared with imported pump, domestic product has price advantage and is widely used. At present, the domestic liquid ring vacuum pump manufacturers should mainly improve their products in the aspects of weight reduction, volume reduction, energy consumption reduction and efficiency improvement
2. Rotary vane vacuum pump is one of the most basic vacuum acquisition equipment. It is a mechanical vacuum pump with oil seal. It is suitable for gas extraction in closed system, such as vacuum packaging, vacuum forming and vacuum suction. However, it can not be used to remove the gas with high oxygen content, corrosive to metal, chemical reaction with pump oil and containing particle dust, nor water or other liquids. Rotary vane pump has the advantages of small volume, small weight and low noise, and can obtain high vacuum degree. The domestic rotary vane vacuum pump has reached the standard in technology, and the price is far lower than that of the imported pump, so it has a certain competitive advantage.
3. Slide valve vacuum pump is a kind of oil sealed variable volume vacuum pump, which can be used to extract general gas or contain a small amount of gas condensable gas. Compared with rotary vane vacuum pump, it has the advantages of working under high pressure (104pa), large amount of air extraction, use in harsh working conditions and durability. It is mainly used in vacuum smelting, vacuum drying, vacuum impregnation, vacuum distillation, etc aspect. The casting of slide valve pump is heavy and the processing workload is heavy. Therefore, many foreign manufacturers hope to cooperate with domestic vacuum pump enterprises. In order to speed up the replacement of imported products, the domestic slide valve pump needs to optimize its products in terms of reducing vibration and noise, preventing oil injection and oil leakage.
4. Roots vacuum pump has the advantages of fast start-up, low power consumption and high pumping speed. It can remove the gas containing water vapor and dust, and can quickly remove the gas suddenly released. The use of Roots vacuum pump can reduce the pumping time and improve the production efficiency. At present, the domestic roots vacuum pump has a small market share compared with the imported products. In order to seize the domestic market and enter the international market, domestic enterprises need to improve the domestic products in terms of reducing vibration noise, solving shaft seal oil leakage, and improving the smoothness and cleanliness of the pump
5. Dry spiral vacuum pump is a relatively new vacuum acquisition equipment, which has the characteristics of high reliability, long service life, good dynamic balance performance, strong adaptability and multiphase mixed transportation. It can remove corrosive, toxic, dust containing gases and condensable steam and other gases. Dry pump has a wide range of applications, including semiconductor industry, chemical industry, film industry, etc. the demand from these three industries is the main driving force of dry pump market. In the semiconductor industry in Europe and America, about half of the enterprises use dry vacuum pump instead of oil seal mechanical pump. At present, the application of domestic dry vacuum pump is less than 1%, and the market share is less than 1%. China’s semiconductor industry mainly uses imported dry-type pump. Therefore, we should strengthen the research and development of domestic dry-type vacuum pump, and make the dry-type vacuum pump become the new economic growth point of China’s vacuum industry
After a long time of development, there are many types and application fields of vacuum pump. Each type of vacuum pump has different excellent characteristics and performance. The enterprise should consider how to select the vacuum pump according to its operating conditions, vacuum requirements and other factors. At present, China’s vacuum industry should pay attention to the upgrading of domestic vacuum pump products, seize more domestic market and enter the international market