TURBOVAC pumps

TURBOVAC pumps are precisely balanced and may generally be connected directly to the apparatus. Only in the case of highly sensitive instruments, such as electron microscopes, is it recommended to install vibration absorbers which reduce the present vibrations te a minimum. For magnetically suspended pumps a direct connection to the vacuum apparatus will usually do because of the extremely low vibrations produced by such pumps. 

Any commercially available vacuum pump is perfectly fine for the underground chemist s needs but the best kind to buy is a diaphragm pump, which is more resistant to the often-harsh chemical vapors that are sucked through it. Most vacuum pumps cost about 100- 200. However, the stronger the vacuum the better. If a chemist is looking to pull 1mm of Hg (don t ask) like the girls in the chemistry papers do then she can be looking at a turbovac that can run well over 5000. 

This agrees - as expected - well (order of magnitude) with the experimentally determined value for kg (Nj) = 2.0 10 from Fig. 2.55. In view of the optimizations for the individual rotor stages common today, this consideration is no longer conect for the entire pump. Shown in Fig. 2.56 are the values as measured for a modern TURBOVAC 340 M. 

Fig. 2.52 Schematic diagram of a grease lubricated TURBOVAC 151 turbomolecular pump...

Fig. 2.54 Pumping speed curves of a TURBOVAC 600 forH He, N2 andAr...

Fig. 2.56 Maximum compression kg of a turbomoiecuiar pump TURBOVAC 340 M for Fl2, He and Nj as a function of backing pressure...

LEYBOLD manufactures pumps such as the TURBOVAC 55 with an integrated Holweck stage (screw-type compressor) and, for example, the HY.CONE 60 or HYCONE 200 with an integrated Siegbahn stage (spiral compressor). The required backing pressure then amounts to a few mbar so that the backing pump is only required to compress from about 5 to 10 mbar to atmospheric pressure. A sectional view of a HY.CONE is shown in Fig. 2.52a. 

If the container is evacuated with a TURBOVAC 50 turbomolecular pump, for example (S = 50 I/s), which is attached to the vacuum vessel by way of... 

Naturally it is possible to improve this ultimate pressure, should it be insufficient, by using a larger-capacity pump (e.g. the TURBOVAC 151) and at the same time to reduce the pump-down time required to reach ultimate pressure. 

As shown in the right side of Fig. 9, a quadrupole mass spectrometer, MSG 300, with a gas-tight ion source, secondary electron multiplier, direction detector, and a turbo-molecular pump (TURBOVAC 150) is equipped with a membrane inlet (all from Nippon Shinku, Tokyo). The resolution scale is 300. Mass spectrometry can also be used for the measurement of dissolved gases in a liquid phase using a steam sterilizable membrane probe. Recently, the application of the mass spectrometer to fermentation processes has increased markedly. 

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