(1) A larger pumping speed in a wider pressure range;
(2) The rotor has good geometric symmetry, so the vibration is small and the operation is stable. There are gaps between the rotors and between the rotor and the shell, no lubrication is required, and the friction loss is small, which can greatly reduce the driving power and achieve a higher speed;
(3) There is no need for oil sealing and lubrication in the pump cavity, which can reduce the pollution of oil vapor to the vacuum system;
(4) There is no compression in the pump cavity and no exhaust valve. The structure is simple and compact, and it is not sensitive to dust and water vapor in the exhausted gas;
(5) The compression is relatively low, and the hydrogen pumping effect is poor;
(6) The surface of the rotor is a curved cylindrical surface with a more complicated shape, which is difficult to process and inspect.
