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Vacuum technology is established in research and industry since the beginning of the 19th century and is undergoing rapid development since. In research and in most branches of industry today, it is indispensable.
Corresponding to the many areas of application, the number of technical procedures in vacuum processes is extraordinarily large. These cannot be described within the scope of this section, because the basic calculations in this section cover mainly the pumping process, not the process taking place in the evacuated system. Examples of important processes in vacuum technology and the pressure regions in which these processes are mainly carried out are given in the diagrams (Figures 2.71 and 2.72).
Generally, the pumping operation for these processes can be divided into two categories: dry and wet vacuum procedures; that is, into processes in which no significant amounts of vapor have to be pumped and those in which vapors (mostly water or organic) arise.
Distinctions between the two categories are described briefly:
The system is usually evacuated to a suitable characteristic pressure before the actual working process begins. This happens, for example, in plants for evaporative coating, electron-beam welding, and crystal pulling; in particle accelerators, mass spectrometers, electron microscopes; and others.
Further, there are dry processes in which degassing in vacuum is the actual technical process. These include work in induction and arc furnaces, steel degassing plants, and plants for the manufacture of pure metals and electron tubes.
Next to this we have rough vacuum processes as vacuum clamping, forming or transport, where a certain pressure corridor is maintained, e.g., by buffer volume
This is especially important in the drying of solid materials. If, for instance, work is undertaken prematurely at too low a pressure, the outer surfaces dry out too quickly. As a result, the thermal contact to the moisture to be evaporated is impaired and the drying time is considerably increased. Predominantly processes that are carried out in drying, impregnating, and freeze-drying plants belong in this category.
In the removal of water vapor from liquids or in their distillation, particularly in degassing columns, vacuum filling, and resin-casting plants, as well as in molecular distillation, the production of as large a liquid surface as possible is important. In all wet processes the provision of the necessary heat for evaporation of the moisture is of great importance.
Basic pumping procedures are covered in the pages linked to the pumping processes section.
If you have specific questions, you can get in touch with a specialist department in Leybold where experts who can draw on many years of experience are available to you.
Rough vacuum 1013 mbar – 1 mbar
Ø Holding, Lifting, Packaging, Drying, Distillation, and Steel Degassing.
Medium vacuum 1 -10-3 mbar
Ø Sputtering coating, Molecular distillation, freeze-drying, impregnation, melting and casting furnaces, and arc furnaces.
High vacuum 10-3 – 10-7 mbar
Ø Evaporative coating, vacuum brazing, mass spectrometers, tube production, electron microscopes, electron beam plants, and particle accelerators.
Ultrahigh vacuum: < 10-7 mbar
Ø Nuclear fusion, storage rings for accelerators, space research, and surface physics.