© Edwards Limited 2008. All rights reserved. Page 21
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Installation
B753-03-880 Issue F
3.5 Purge gas connection
3.5.1 Connect the purge gas
If you want to supply a purge gas to the pump, fit a vent port adaptor (see Section 7.4.7) in place of the blank plug
(Figure 4 or 5, item 3). Connect your gas supply to the purge port.
You must limit the flow rate of the purge gas to the allowed range, also specified in Section 2.4. To limit the flow
rate, use a flow controller or a pressure regulator and calibrated flow restrictor. The PRX10 purge restrictor accessory
(see Section 7.3) is suitable for this purpose. Adjust the PRX10 as described in the instruction manual supplied with
the accessory.
3.5.2 Recommended purge gas flow
The recommended purge gas flow for typical applications is 25 sccm (0.42 mbar l s
-1
, 42 Pa l s
-1
). This flow will protect
the pump when you pump oxygen in concentrations above 20% by volume.
3.6 Electrical installation
Always make the electrical connections to the EXT pump after the pump has been installed on your vacuum system.
The EXT pump should be electrically bonded to earth (ground) using the connection provided (Figure 4 or 5, item 8).
The EXC Controller provides the electrical supply to the EXT pump through the multiway pump-to-controller cable.
Connect and lock the bayonet-connectors at the ends of the cable to the mating connectors on the pump and the EXC
Controller.
The EXC Controller is designed to allow a pumping system to be configured in a variety of ways, from a basic
manually-operated system to a fully automatic system with remote control. Refer to the instruction manual supplied
with the EXC Controller to complete the electrical installation.
3.7 Cooling
3.7.1 Introduction
You must cool the pump by forced-air or water-cooling to prevent damage to the bearing lubricant.
We recommend that wherever possible, you cool the pump by forced-air or water-cooling.
You must use water-cooling in any of the following operating conditions:
z Backing pressure >10 mbar (1000 Pa).
z Backing pressure > 8 mbar (800 Pa) and interstage flow > 30 sccm (0.5 mbar l s
-1
, 50 Pa l s
-1
).
z Backing pressure > 5 mbar (500 Pa) and interstage flow > 80 sccm (1.3 mbar l s
-1
, 130 Pa l s
-1
).
z Ambient temperature > 35 °C.
z When you use a bakeout band.
In all other operating conditions, you can use forced-air cooling. If you use forced-air to cool the pump, you must
ensure that there is an adequate supply of cooling-air to the pump.
During operation, if the temperature of any surface of the pump is higher than 50 °C, the pump is too hot and you
must increase the cooling.
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