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Mechanical vacuum pumps that use oil to maintain the sealing of moving parts and achieve pumping by changes in the volume of the pump chamber are collectively referred to as oil-sealed vacuum pumps. Their working principle is to mechanically increase and decrease the volume of the pump chamber to evacuate air. When the volume of the working chamber inside the pump becomes minimal, it is connected to the pump’s inlet pipe, allowing gas to enter the pump’s suction chamber, until the volume of the suction chamber reaches its maximum and it becomes separated from the air inlet again. When the volume decreases, the gas is compressed until its pressure exceeds one atmosphere, at which point the exhaust valve opens to release the gas. The necessity of using oil as the sealing pump fluid: The mechanical vacuum pumps that are widely used today, even when designed to the best of standards and with high precision in the fit between the moving parts facing each other. When the pump reaches ultimate vacuum, it is also difficult to prevent gas from \"breaking through\" and flowing back from the low-vacuum side to the inlet side. Furthermore, the inevitable presence of harmful voids in the design, manufacturing, and assembly of the pump also reduces its ultimate vacuum level. An oil-sealed vacuum pump uses oil to seal the moving parts that move towards each other as well as the components of the exhaust valve ； Filling the harmful space reduces the chances of high-pressure gas from \"breaking through\" significantly, improving the sealing performance and thus enabling the pump to achieve a higher level of vacuum. Applications of oil-sealed vacuum pumps: Oil-sealed vacuum pumps can be classified into four types based on their structural design: fixed-vane type, rotary-vane type, slide-valve type, and epicyclic type. At present, the oil-sealed vacuum pump is the most widely used type of pump in domestic vacuum generation technology. It can be used alone as an exhaust pump for low-vacuum equipment, or as a pre-vacuum pump for high-vacuum exhaust applications. The oil-sealed mechanical vacuum pumps widely used in the vacuum industry are mostly medium and small rotary vane pumps, as well as medium and large sliding vane pumps. Therefore, it is playing an increasingly important role in many sectors of the national economy, such as industries related to electro-vacuum technology, electronics, light chemical engineering, steel production, and non-ferrous metal smelting. Since oil-sealed vacuum pumps are equipped with gas traps, they can also evacuate humid gases. But it is not yet suitable for extracting gases with high oxygen content, which are explosive, corrosive to ferrous metals, chemically reactive toward pump seal oils, and containing particulate dust. Currently, many research institutions and manufacturers in China are designing and producing vapor-extraction and corrosion-resistant oil-sealed vacuum pump series. With the development and application of new technologies and materials, various oil-sealed vacuum pumps with improved performance, capable of meeting various industrial requirements and possessing strong adaptability will surely be produced.