In the area of semiconductor technology, Roots vacuum pumps are
found in etching processes among others, and in use with dry
compressing vacuum pumps. The pumping speed of the combination
of backing pumps amounts to 200 to 500 m3/h (118 to 295 cfm) and it
ensures a cut-in pressure of 10-1 mbar (0.75 x 10-1 Torr) for the
turbomolecular pump. In the case of
dry compression, corrosive gases which also have a high particulate
content must be pumped.
Canned motors and PFPE fluids provide a good seal against the
outside and allow long periods
between servicing, high reliability and thus very low operating
costs (WS PFPE types).
Specific suitable for this processes and use in clean rooms are
Roots vacuum pumps filled with PFPE and water-cooled motors.
These kind of motor has only a little heat dissipatoion.
Central Vacuum Supply Systems
Large Roots vacuum pumps, usually in connection with single-stage
rotary vane vacuum pumps serve several consumers of vacuum
(packaging machines, for example) at the same time.
Due to the uncontrolled influx of gas, a high of pumping speed must
be attained quickly, in order to keep the vacuum (1 to 30 mbar (0.75
to 22.5 Torr)) permanently available to all consumers. This in
particular, is implemented by Roots vacuum pumps having a pressure
equalization line (WAU types).
Chemistry
Replacement of vapor jet or gas jet pumps on liquid ring pumps in
drying and distillation plants is necessary for attaining the
required operating pressure of about 1 mbar (0.75 Torr).
Reduction of operating costs by entirely eliminating vapor or gas
quantities includes separation of these on the pressure side (WA and
RA types).
Laser Systems
Continuous circulation of the gas in order to remove heat from a
closed cycle in which pressure differentials of up to 100 mbar (75
Torr) must be maintained. The tough requirements regarding purity
necessitate a total absence of contamination by oil and dust. This
is ensured by reducing the pressure level in the oil chambers as
well as by coating the pump chamber. The pumps are assembled and
tested under clean room conditions. The canned motor ensures a
high degree of leak-tightness to the outside and permits operation
in connection with a frequency converter (WSLF types).
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