B722-20-880 Issue D
Page 6 © Edwards Limited 2008. All rights reserved.
Edwards and the Edwards logo are trademarks of Edwards Limited.
Technical data
2.2.1 Pumps without gas purge
The pumps are designed to pump the following residual gases normally used in high-vacuum systems:
The pumps may be used to pump oxygen and water vapour, subject to the following conditions:
If you wish to pump a gas not in the list above, contact your supplier for advice. If you do not contact your supplier,
you may invalidate the warranty on the pump. The pumps are not suitable for pumping aggressive or corrosive gases.
2.2.2 Pumps with gas purge (EXT255H 24 V and EXT255Hi 24 V only)
When purged with an inert gas, the pumps can be used to pump oxygen in concentrations above 20% by volume.
2.3 Vent gas specification and vent control data
Although the pump may be vented to atmospheric air, high relative humidity of the air may greatly increase the
subsequent pumping time. To reduce pump-down times, vent the pump with dry, clean gases.
z Air z Carbon monoxide z Neon z Ethane z Methane
z Nitrogen z Krypton z Argon z Propane
z Carbon dioxide z Helium z Hydrogen z Butane
z Oxygen The oxygen concentration must be less than 20% by volume
z Water vapour You must ensure that vapour does not condense inside the pump; refer to Section 3.7.3.
Vent gas Dry air, nitrogen, argon or other inert gases
Maximum dew point at atmospheric pressure - 22 °C
Maximum size of particulates 1 µm
Maximum concentration of oil 0.1 parts per million
Time for rotational speed to reach 50% 15 s
Maximum allowed rate of pressure rise See Figure 1
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