2. Trends in the development and use of turbomolecular pumps

Abstract

After a review of the developments in the field of turbomolecular pumps during the last 20 years, the actual technical situation is treated. Turbomolecular pumps of different design with pumping speeds from 110 l/s to about 9000 l/s are offered on the market. The influence of the most important constructive parameters—geometry of the rotor, configuration of the blades and the rotor speed—on the essential performance characteristics of turbomolecular pumps—pumping speed and compression—is explained. Single flow (′svertical′) and dual flow (′horizontal′) turbomolecular pumps are considered under the aspects of manufacturing costs, vibration levels, reliability and after sales service. Beside the ′classic′ rotor bearings on the basis of oil lubricated ball bearings for the last few years there are also some types of turbomolecular pumps with so-called ′dry′ bearings on the market. These turbomolecular pumps with gas or with electro-magnetic rotor bearings have, for reason of the complex design of the bearing, prices which are almost twice as high than those of turbomolecular pumps with classic bearings. Finally the trends in the field of further developments of turbomolecular pumps with classic or dry bearings and some of their main applications are dealt with.