Solid State Flowmeter Installation; Pump Used With Corrosive Gases - Varian E-series Manual De Instrucciones

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.
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TECHNICAL INFORMATION

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 supplied
to the pump through the integrated purge valve. A
pressure regulator can be installed between 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.
! ! ! !
CAUTION
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.
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
87-900-942-01(A)