Pump Used With Corrosive Gases - Varian TV 301 Manual De Instrucciones

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.
!
CAUTION
To prevent bearing damage, Varian 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 Var-
ian for specific applications.
The purge gas throughput with the recommended
3
forepump of 15 m /h (11 CFM) allows to achieve
a high vacuum pressure in the 10
The recommended gas flow maintains a pressure
into the pump body higher than the forevacuum pres-
sure.
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. Open the Turbo-V vent port slowly until to
reach atmospheric pressure in the system.
4. Turn off the Turbopump.
5. When the Turbo-V pump and the backing
pump are stopped and the system is at at-
mospheric pressure, for a better bearing pro-
tection it is advisable to leave the purge gas
flowing into the Turbo-V pump, with the
chamber or the Turbo-V vent valve opened,
to avoid system overpressures. If the vent
valve can't be kept opened, the backing
pump should be left operating.
All manuals and user guides at all-guides.com
-8
mbar range.
46
TECHNICAL INFORMATION
1. Purge gas line
2. Pressure regulator
3. Gas purge valve
4. Gas purge port
5. Forevacuum pump
6. Turbopump
7. Vent valve
Purge layout
87-900-946-01(B)