Front stage vacuum pump in vacuum application

The pump which can provide the necessary pre stage pressure for other pumps which can not directly exhaust to the atmosphere is called the front stage pump. Among them, some pumps can work in two ways, sometimes discharged into the atmosphere, and sometimes discharged into the pre pressure of decompression. 

All types of pumps can exhaust air to the atmosphere, but their effective working area depends on their working principle. If the sealing fluid is not used, the high compression ratio cannot be maintained, and the mechanical clearance cannot be made small enough to effectively prevent the secondary expansion or backflow. Pumps without sealing fluid are suitable for working near atmospheric pressure. Because it is difficult to dissipate the heat of compression, some dry mechanical pumps, especially roots pump and thousand screw compressor, are limited in their low pressure and strong operation. These pumps should work above 30otorr. If materials such as carbon, graphitized cast iron and high temperature synthetic materials are used, the working area of dry vane pump can be extended to 150 Torr due to the self-lubricating property of these materials. In the same pressure area, liquid ring pump, reciprocating piston pump and lower efficiency jet pump can be effectively used. If double-stage liquid ring pump, valveless multi-slice pump, double-stage reciprocating piston pump, liquid jet pump and double-stage steam jet pump are used, the pressure area can even be extended to about 30 Torr. When the working pressure is further reduced, the relatively simple pump may no longer be applicable, and the multi-stage rotary oil seal pump must be used, and the sealing fluid with low steam pressure must be selected. 

The effective working pressure of single-stage pump is mainly due to the influence of oil pollution, so it is limited to 0.l Torr. Due to the same influence, the low pressure working limit of the two-stage oil seal pump is slightly lower than 10mtorr. The oil vapor pressure arc of about 1mtorr makes roots pump with two-stage oil seal pump (at effective pumping speed) unable to work in 10-6 Torr area. It is more effective to use other pumping equipment, such as diffusion pump, ion pump, etc., for pumping air below 1mtorr. As far as mechanical pumping is concerned, turbomolecular pumps are best used in this area.

CL Sereis Cone Liquid Ring Vacuum Pump

Roots Blowers

Roots Vacuum Pump