When one type of pump cannot meet the pumping and vacuum requirements, several pumps need to be combined to complement each other to meet the process requirements. 

The Screw-roots Vacuum Pump Unit composed of the Roots vacuum pump as the main pump and the screw vacuum pump as the backing pump is more suitable for working under low pressure than a single screw vacuum pump. The dry screw vacuum pump is a pumping device that uses a pair of variable-pitch screws to perform synchronous high-speed reverse rotation in the pump casing to produce suction and exhaust. The two screws are adjusted by fine dynamic balance and supported by bearings. Installed in the pump casing, there is a certain gap between the screw and the screw, so when the pump is working, there is no friction between each other, the operation is stable, the noise is low, and the working cavity does not need lubricating oil. Therefore, the dry screw pump can extract Gas occasions with a large amount of water vapour and a small amount of dust. Water temperature has little effect on the vacuum, saving water by more than 90%, even without water consumption. No fuel consumption, no dripping. There is no friction between the rotating parts, it can run at high speed, and the whole machine is small in size. 

Screw-roots Vacuum Pump Unit are widely used in pharmaceutical, chemical, coating, vacuum furnace, semiconductor and other industries.