(1) There is a large pumping speed in a wide range of pressure;

(2) The rotors have excellent geometric symmetry, so the vibration is small and the operation is stable. There are gaps between rotors and between rotor and shell, which do not need lubrication and have small friction loss, which can greatly reduce the driving power and realize higher speed;

(3) The pump chamber does not need oil sealing and lubrication, which can reduce the environmental pollution of oil vapor to the vacuum system;

(4) There is no compression or exhaust valve in the pump chamber. The structure type is concise, compact and insensitive to dust and water vapor in the extracted gas;

(5) Low compression ratio and poor pumping effect on hydrogen;

(6) The rotor surface is a curved cylindrical surface with complex shape, which is difficult to process and inspect.