Edwards nEXT85 User Manual

supplied, it is recommended to either limit the vent or only open the vent valve aer the
pump speed has fallen to 50% of full rotaonal speed. Do not vent from the backing line as
this may lead to contaminaon. If venng into the vacuum system and using an oil sealed
rotary backing pump, select a point upstream of the pump, to prevent oil back-streaming
from the backing line. Table 8 on page 48 gives an indicaon of the appropriate orice size
to be ed to the vent-valve for given vacuum system volumes in order that the vent rate is
kept within the limits given in Venng gas specicaon and vent control data on page 89.
To maintain the cleanliness of the vacuum system, venng the pump (or vacuum system) is
recommended whenever switching the pump
o.
Manual vent valve
Edwards recommends that the manual vent valve is opened only aer the pump speed has
fallen to 50% of full rotaonal speed.
A manual vent valve is supplied with the nEXT85 pump. It is not possible to accurately control
the rate of pressure rise using the manual vent valve so take care not to open it too quickly.
TAV5 solenoid vent valve
The TAV5 solenoid valves can be purchased as accessories and come either pre-wired with an
auxiliary connector ed or as a bare-wire opon.
Both 'Normally Closed' and 'Normally Open' valves are available, refer to Accessories for the
nEXT85 on page 78.
Venng may be accomplished by one of the following means, and by using the procedure
below:
• Use the TAV5 solenoid vent valve in the manual vent valve posion.
• Use the TAV5 solenoid vent valve connected to a convenient ange on the vacuum
system.
• Use an alternave vent valve, with an appropriate restricon, connected to the
vacuum system.
When using the TAV5 vent valve, the pump may only be hard vented when it is at full speed if
the vacuum system has a volume of 5 litres or more.
If the volume of the vacuum system is less than 5 litres, incorporate a suitable vent restrictor
and vent the pump when it is at full speed or else use the controlled venng opon. Table 8 on
page 48 gives an indicaon of the appropriate orice size to be ed to the vent valve for
given vacuum system volumes in order that the rate of pressure rise remains within the limits
shown in Venng gas specicaon and vent control data on page 89.
Note:
If a vent restrictor is used, the me required to vent the vacuum system may be unacceptably
long. The me may be reduced by using a vent valve without a vent restrictor and waing
unl the pump speed has fallen to 50% of full rotaonal speed before opening the vent valve.
Vent valve control
The TAV5 solenoid valve can be controlled by the nEXT85 motor controller or by an Edwards
TIC Turbo Instrument Controller.
The nEXT85 controller can control the rate of
venng, using the vent valve opons in Table 6 on
page 46. Using this feature the pump can be vented from full rotaonal speed in a controlled
manner that will not damage the pump bearings. Once the pump rotaonal speed has dropped
B8G0-00-880A -
Operaon of the nEXT85
Page 45

Edwards nEXT85 Specifications

General

Brand	Edwards
Model	nEXT85
Category	Water Pump
Language	English