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GAS PURGE VALVE INSTALLATION
A gas purge valve is available to protect the pump
bearings against particulate and corrosive gases
that could move into the pump.
To install the gas purge valve it is necessary to
unscrew the purge port cover as shown in the
following figure,
and then screw the gas purge valve (with a torque
of 2.5 Nm) as shown in the following figure.
PUMP USED WITH CORROSIVE GASES
To prevent damage to the bearings, an inert gas
must flow into the pump body around the upper
bearing towards the forevacuum line.
To supply the inert purge gas (e. g. nitrogen) to the
pump through the purge port, connect a gas purge
valve between the pressure regulator and the
pump (see the following figure). Adjust the pres-
sure regulator in order to obtain the necessary gas
purge flow rate according to the application.
!
To prevent bearing damage, Varian suggests the
following purge gas flow rates: 10 sccm (0.17
mbar l/s) for a mild purge process, or 20 sccm
(0.34 mbar l/s) for an heavy process. Please con-
tact Varian for specific applications.
The purge gas throughput with the recommended
3
forepump of 15 m
high vacuum pressure in the 10
The recommended gas flow maintains a pressure
into the pump body higher than the forevacuum
pressure.
58
TECHNICAL INFORMATION
CAUTION
/h (11 CFM) allows to achieve a
-9
mbar range.
87-900-969-01(B)
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