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VENT VALVE INSTALLATION
It is possible to use the vent port on the envelope
to connect an external vent valve: unscrew the
threaded plug and screw the vent valve into the
pump.
PUMP PURGING AND VENTING
Models 969-8888 and 969-8889 are equipped with
an integrated purging and venting valve device.
Both valves are fed through a single gas port, with
1/8 NPT thread or Swagelok connector.
Purge and Vent Installation
To install the gas purge and vent line it is neces-
sary to unscrew the purge/vent port cover, and
then connect the gas line.
Reason to purge the Turbo-V 3K-G pump dur-
ing operation
Keep the gas purge on at all times during pump
operation, during stops, and even if there is no
flow of aggressive gases.
This will keep the pressure in the bearings area
higher than in the foreline and will prevent pollution
or powder from flowing back, mainly into the bear-
ings area.
Therefore, to prevent contamination and damage
to the bearings, an inert gas must flow into the
pump body around the upper bearing towards the
forevacuum line.
CAUTION
Disrespect of these simple, basic rules may cause
seriously damage the pump bearings and void
pump warranty.
How to purge the Turbo-V 3K-G pump
To supply the inert purge gas (e. g. nitrogen) to the
pump through the purge port, connect a gas purge
line to the pump.
The purging device automatically provides about
20 sccm when fed with 1 bar (14 psi) absolute (at-
mospheric pressure).
CAUTION
To prevent bearing damage, Varian suggests a
minimum purge gas flow rate of 20 sccm (0.33
mbar l/s). This value can be exceeded, according
to the process requirements. Please contact Var-
ian for specific applications.
How to vent the Turbo-V 3K-G pump
The recommended procedure to vent the system
is described in the following points:
1.
Close the process gases flowing into the sys-
tem before sending the STOP signal to the
Turbo-V 3K-G pump.
2.
Leaving the Turbo-V 3K-G pump and the
backing pump running and the purge gas
flowing, wait for enough time to evacuate the
process gases from the system (e.g. to reach
the typical basic process pressure).
3.
Then close the gate valve connecting the
Turbo pump to the chamber (if present) and
the valve connecting the Turbo pump to the
rough pump (if present).
4.
Turn off the Turbo pump by sending the
STOP signal to the controller.
5.
The Turbo-V 3K-G pump will automatically
start the "Controlled Venting Procedure" by
default. This means that the integrated vent
valve will allow a flow of venting gas (e.g. Ni-
trogen), automatically actuated by the control-
ler, in order to slow the rotor down in
controlled manner to a rotational frequency of
100 Hz by adopting the SSR (Stop Speed
Reading) function. All other system opera-
tions should be carried out at rotational fre-
quencies of less than 100 Hz.
6.
When the Turbo-V 3K-G pump and the back-
ing 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 Turbo-V vent valve opened, to
avoid system overpressures.
Evidently, the default settings can be bypassed
and the "Controlled Venting Procedure" can be
eliminated, as explained in a previous section of
this manual.
Additionally, the vent port on the envelope can be
used to connect an external vent valve: unscrew
the threaded plug and screw the vent valve into
the pump to vent pump and system.
The last described venting modalities should be
avoided because they may cause uncontrolled
venting. Please contact Varian if you cannot oper-
ate in the instructed manner.
Uncontrolled venting may seriously damage the
pump and void the pump warranty. Use the Varian
"Controlled Vent Procedure" or contact Varian.
105/107
TECHNICAL INFORMATION
CAUTION
87-901-011-01
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