B777-00-880 Issue E
Page 14
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Edwards and the Edwards logo are trademarks of Edwards Limited.
Installation
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:
z
Use a TAV5 or TAV6 solenoid vent valve accessory (see
) in place of the manual vent valve.
z
Use a TAV5 or TAV6 solenoid vent valve connected to a convenient flange on your vacuum system.
z
Use an alternative valve connected to your vacuum system.
The maximum rate of pressure rise is given in
Figure 3 - Maximum rate of pressure rise when venting
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.
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.
