Oil-free dry mechanical vacuum pump (also referred to as dry mechanical pump) refers to the pump can start pumping under atmospheric pressure, but also will be pumping gas directly to the atmosphere, the pump chamber without oil or other working medium, and Pump ultimate pressure and oil-sealed vacuum pump the same order or close to the mechanical vacuum pump. At present, most of the mechanical vacuum pumps used in the vacuum industry are used as the working medium for the pump with fluids such as oil, water or other polymers, and have various functions such as cooling, sealing and lubrication in the pump. With the development of science and technology and the expansion of vacuum applications, the original mechanical vacuum pump and its composition of the exhaust system there are two urgent needs to solve the problem: First, the pump back to the working fluid pollution was pumping containers, and this return Flow in many cases affect the quality of the product, quantity, increase equipment maintenance costs. Second, due to some of the process of the reaction material in the vacuum pump serious deterioration of the media, so that the pump can not work properly. For normal oil-free vacuum systems, the use of oil-sealed vacuum pumps with attachments such as cold traps or sorption trays prevents backflow but does not completely solve the problem but also complicates the system. The use of the appropriate type of dry mechanical vacuum pump, you can achieve the desired effect. Dry mechanical vacuum pump is widely used, mainly in the following areas: 1) low pressure chemical vapor deposition in the polysilicon preparation process; 2) semiconductor etching process. In these production processes are often used or generate corrosive gases and abrasive particles; 3) In addition to the semiconductor process, some of the particles produced in the process, do not want particles mixed with pump oil, and hope particles discharged pump, then with a certain type Of dry mechanical vacuum pump to meet the requirements; 4) in the chemical industry, pharmaceutical industry, food industry, distillation, drying, defoaming, packaging, to prevent pollution caused by organic solvents, suitable for dry vacuum pump; Oil-free cleaning of the vacuum pump system to prevent oil pollution. In recent years, the rapid development of dry mechanical vacuum pump, a number of large vacuum companies abroad have developed a new type of dry mechanical vacuum pump. Many domestic units have also been engaged in the development of dry mechanical vacuum pump development work, such as Northeastern University, Shenyang Institute of Vacuum Technology, Shanghai Vacuum Pump Factory. At present, dry mechanical vacuum pumps are mainly divided into contact and non-contact type. Contact-type dry pump vane, cam-type, reciprocating piston, diaphragm type, such pumps lower speed, suitable for small capacity high compression ratio (single-stage compression ratio). Non-contact dry pump Roots type, claw type, screw type, scroll type, etc., its high speed, suitable for large capacity, low compression ratio (single stage compression ratio). Different types of dry pumps have their own characteristics. When used according to different purposes to choose from.