BOC Edwards EXT555H, Инструкция по эксплуатации

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Jun 01 Issue A
EXT555H
IN
STALL
A
TION
PAGE
13
13
3.3.4 Interstage connection (Hi pump
variants only)
Use suitable vacuum tube and connectors to
connect the interstage port to your vacuum system
or to the outlet flange of another turbomolecular
pump. Leave the inlet strainer in the interstage port
unless you are sure that debris cannot be drawn into
the interstage port.
3.4 Vent options, vent valve connection
and control
To maintain the cleanliness of your vacuum system
we recommend that, whenever you switch the
pump off, you vent the pump or the vacuum system
when the speed of the EXT555H pump is between
full rotational speed and 50% of full rotational speed.
At and above 50% of full rotational speed the rotor
spins fast enough to suppress any hydrocarbon oil
from your backing pump. Venting may be
accomplished by one of the following methods:
• Use a TAV5 or TAV6 solenoid vent valve
accessory (see Section 7) in place of the
manual vent valve.
• Use a TAV5 or TAV6 solenoid vent valve
connected to a convenient flange on your
vacuum system.
• Use an alternative valve connected to your
vacuum system.
The maximum rate of pressure rise is given in
Figure 3.
When using the manual vent valve supplied you must
only open the vent valve when the rotational speed
of the EXT555H pump has fallen to 50% of full
rotational speed.
If you use a TAV vent valve or other solenoid vent
valve, you should only use the vent valve to vent the
pump from full speed if the vacuum system has a
volume of 20 litres or more. If the system has a
volume of less than 20 litres you should incorporate
a suitable restrictor (see below and Table 7).
Alternatively, if you are using an EXC controller to
operate the vent valve, you can configure the valve
so that it opens once the pump has reached 50% of
full rotational speed.
Do not vent from the backing line as this may lead
to contamination. If you vent into your vacuum
system, select a point upstream of the pump to
prevent oil backstreaming from the backing line.
CAUTION
You must ensure that your vacuum system cannot
suddenly be vented to atmosphere when the pump
is running at full rotational speed - if it does so then
the EXT555H pump may suffer a catastrophic
failure. As the inlet screen is not designed to
contain pump components in the event of a
catastrophic failure, subsequent damage may result
to the connected vacuum system.
CAUTION
If you vent the pump when it is at full rotational
speed and the rate of pressure rise is too high the
pump bearing life may be reduced.
Vacuum system volume (litres) Orifice diameter (mm)
< 20 < 1.0
< 10 < 0.7
< 5 < 0.5
< 2 < 0.35
Table 7 - Vent restrictor orifice diameter (with atmospheric pressure at the inlet)