358
16.
VACUUM TECHNIQUE
'
ical oil pump's. Thus, a rst stage pump of the type shown at the
left is used as its fore pump.
This insures the maximum speed of
operation of each pump.
There are many forms of these mercury condensation pur‘nps,
some of which are constructed entirely of steel and contain two to.
four stages in series.
These are used when a high rate of pump—
ing at low pres3ures
is desired.
Figure 16—5 shows a glass
/.l
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__
.
/
a -
c.
,
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//Ï=È D
C'
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Ë‘
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,
»
,
Fra. .16—5.
A three-stage condensation pump.
_
»
;
,
5pùmpcontainingthræ stages in one. 'The mercury is divided into
three parts, that which passes through 01 creating the fore vacuum
.f'or the:second stage at Cz which, in turn, lowers the pressure for _
the third stage C3.
'
,
'
'
'
.
A three-stage, mercury dilïusio‘n pump with excellent speed
and compact form is shown in gure 16—6‘