YO99-0874-DI-002-18
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2.6 Designing Pumping System
The following is a short note of the knowledge required in using a mechanical booster pump.
The mechanical booster pump cannot be started at the atmospheric pressure and must always
be used in combination with a backing pump (dry pump/rotary pump). Therefore, the vacuum
chamber and the piping must be rough-pumped by the methods shown in the “Fig. 9” and the
mechanical booster pump must be started after the pressure has lowered to its operating range.
The rough-pumping methods include those shown by
①
and
②
in Fig. 9.
The method
①
carries out rough-pumping through the mechanical booster pump. This method is
used when the vacuum chamber is small in size, that is, when a long time can be spent for
rough-pumping. Since the mechanical booster pump does not operate when rough-pumping is
under way, the gas to be exhausted is discharged through the clearances between the rotors in
the mechanical booster pump. This increases the pumping resistance (decreases conductance)
and a long rough-pumping time is required.
In the method
②
, a rough-pumping circuit is provided for the mechanical booster pump. This
method is used when the vacuum chamber is large in size, that is, when it is desired to shorten
the rough-pumping time.
Rough-pumping is carried out with the main valve and the roughing valve opened and, when the
specified pressure is attained, the mechanical booster pump is actuated and the roughing valve
is closed for high vacuum pumping.
Fig. 9 Evacuation by mechanical booster pump (example)
Summary of Contents for PRC-003A
Page 10: ...YO99 0874 DI 002 18 ix Fig 1 Warning Label PRC 003A PRC 006A PRC 012A PRC 018A...
Page 24: ...YO99 0874 DI 002 18 8 2 4 Dimensional drawing Fig 3 PRC 003A Dimensional drawing...
Page 25: ...YO99 0874 DI 002 18 9 Fig 4 PRC 006A Dimensional drawing...
Page 26: ...YO99 0874 DI 002 18 10 Fig 5 PRC 012A Dimensional drawing...
Page 27: ...YO99 0874 DI 002 18 11 Fig 6 PRC 018A Dimensional drawing...
Page 57: ...YO99 0874 DI 002 18 41 Fig 15 PRC 006A Optional attachment figure...
Page 58: ...YO99 0874 DI 002 18 42 Fig 16 PRC 012A Optional attachment figure...
Page 59: ...YO99 0874 DI 002 18 43 Fig 17 PRC 018A Optional attachment figure...
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