If the LEDs do not light up as expected, or if the red or yellow LEDs begins to flash a
repeated sequence or if the red LED is lit, refer to Fault finding on page 110. If the
bearing LED is lit or flashing refer to Bearing monitoring and conditioning system on
page 120.
7.2 Vent options, vent valve connection and control
Note:
If manually venting the pump when it is at full rotational speed and the subsequent rate
of pressure rise is too high, the pump life may be reduced. When using the manual vent
valve supplied, it is recommended to either limit the vent or only open the vent valve
after the pump speed has fallen to 50% of full rotational speed. Do not vent from the
backing line as this may lead to contamination. If venting 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: Vent restrictor orifice diameter if venting
the vacuum system chamber gives an indication of the appropriate orifice size to be
fitted to the vent-valve for given vacuum system volumes in order that the vent rate is
kept within the limits given in Vent gas specification and vent control data on page 34.
To maintain the cleanliness of the vacuum system, venting the pump (or vacuum system)
is recommended whenever switching the pump off.
7.2.1 Manual vent valve
Edwards recommends that the manual vent valve is opened only after the pump speed
has fallen to 50% of full rotational speed.
A manual vent valve is supplied with the nEXT 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.
7.2.2 TAV5 or TAV6 solenoid vent valve
The TAV solenoid valves can be purchased as accessories and come either pre-wired
with an auxiliary connector fitted or as a bare-wire option.
Both 'Normally Closed' and 'Normally Open' valves are available, refer to Accessories on
page 123.
Venting may be accomplished by one of the following means, and by using the
procedure below:
▪ Use the TAV solenoid vent valve in the manual vent valve position.
▪ Use the TAV solenoid vent valve connected to a convenient flange on the vacuum
system.
▪ Use an alternative vent valve, with an appropriate restriction, connected to the
vacuum system.
When using the TAV 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 use the controlled venting
option. Table: Vent restrictor orifice diameter if venting the vacuum system chamber
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