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SOLID STATE FLOWMETER INSTALLATION
A gas purge valve is integrated to protect the
pump bearings against particulate and corrosive
gases that could move into the pump.
To the purge valve can be connected a solid state
flowmeter model 969-9114 (see the following figure)
or model 969-9115, operating in the range from 0 to
150 SCCM with Nitrogen, and from 0 to 125 SCCM
with Argon, that connected to the controller can
monitor the flow of the protective gas purge.
The following figure shows the connector of the
flowmeter to the controller.
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.
The inert purge gas (e. g. nitrogen, argon) is sup-
plied to the pump through the integrated purge
valve. A pressure regulator can be installed be-
tween the purge valve and the gas purge source.
Adjust the pressure regulator in order to obtain the
necessary gas purge flow rate of 20 sccm.
The standard gas purge may be supplied with 1
atm (15 psig) to get 20 sccm.
To prevent bearing damage, the integrated purge
valve is foreseen for a gas flow rate of 20 sccm
(0.34 mbar l/s). Please contact Varian for specific
applications.
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.
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.
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TECHNICAL INFORMATION
CAUTION
1. Purge gas line
2. Pressure regulator
3. Solid state
flowmeter
4. Gas purge valve
(integrated into
the pump)
5. Forevacuum
pump
6. Turbopump
7. Vent valve
8. Controller
87-900-900-01(C)
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