Agilent Technologies 869-8928R003, User Manual

Page: 255 / 264

Technical Information
Pump Used with Corrosive Gases
17
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CAUTION!
To prevent bearing damage, Agilent suggests a minimum purge gas flow rate of
10 sccm (0.17 mbar l/s). This value can be exceeded, according to the process
requirements. Please contact Agilent for specific applications.
The purge gas throughput with the recommended forepump of 15 m
3
/h (11 CFM) allows to achieve a high vacuum pressure in the 10
-8
mbar range.
The recommended gas flow maintains a pressure into the pump body
higher than the forevacuum pressure.
The recommended procedure to vent the system and the pump
avoiding the contact between the pump bearings and the corrosive
gas is described in the following points:
1.
Close the corrosive gas flow into the system.
2.
Leaving the Turbo-V pump and the backing pump running and
the purge gas flowing, wait for enough time to evacuate the
corrosive gas from the system.
3.
Turn off the Turbopump.
4.
Open the vent port slowly until to reach atmospheric pressure in
the system.
5.
When the Turbo-V pump and the backing pump are stopped and
the system is at atmospheric pressure, for a better bearing
protection it is advisable to leave the purge gas flowing into the
Turbo-V pump, with the chamber or the vent valve opened, to
avoid system overpressures. If the vent valve can't be kept
opened, the backing pump should be left operating.