Pump Used With Corrosive Gases - Agilent Technologies TwisTorr 74 FS Notice De Mode D'emploi

17 Technical Information

Pump Used with Corrosive Gases

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.
Adjust the pressure regulator in order to read a gas flow rate of 0.1 to
0.8 mbar l/s.
To prevent bearing damage, Agilent suggests a minimum purge gas flow rate of
CAUTION!
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
3
m /h (11 CFM) allows achieving 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
2
3
4
5
342/352
Close the corrosive gas flow into the system.
Leave the Turbo pump and the backing pump running and the
purge gas flowing, wait for enough time to evacuate the corrosive
gas from the system.
Turn off the Turbopump.
Open the Turbo vent port slowly until to reach atmospheric
pressure in the system.
When the Turbo 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 pump, with the chamber or the Turbo vent valve opened,
to avoid system overpressure. If the vent valve can't be kept
opened, the backing pump should be left operating.
TwisTorr 74 FS User Manual / 87-901-053-01 (A.00)