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Page 41
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Installation
B800-00-880 Issue A
If you connect a vent valve to your vacuum system, select a point upstream of the nEXT pump to prevent
backstreaming of oil from the backing pump.
If 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 using the TAV6 vent-valve, the pump may only be hard vented when it is at full speed
if the vacuum system has a volume of 10 litres or more.
If the volume of your vacuum system is less than 5 litres (when using a TAV5 vent-valve), or if the volume of your
vacuum system is less than 10 litres (when using a TAV6 vent-valve), you can incorporate a suitable vent-restrictor
and vent the pump when it is at full speed.
gives an indication of the appropriate orifice size to be fitted
to the vent valve for given vacuum system volumes in order that the rate of pressure rise remains within the limits
shown in
.
Note:
If you use a vent-restrictor, you may find that the time required to vent your vacuum system is unacceptably
long. You may be able to reduce the vent time if you use a vent-valve without a vent-restrictor and wait
until the pump speed has fallen to 50% of full rotational speed before you open the vent-valve.
3.8.3
Controlled venting
The TAV5 or TAV6 solenoid valve can be controlled by the Controller electronics. To use this function, fit the
electrical connector supplied with the pump to the lead of the TAV5 or TAV6 solenoid valve. To ensure cable cores
and screen are wired correctly, follow the electrical connection instructions given in the Accessories Manual
(supplied with the TAV valve) and refer to
and
. Plug the connector into the socket at the side of
the Controller (refer to
.
The Controller is capable of controlling a number of different venting options, these are defined in
.
When you receive your pump, the Controller will be configured with the factory default vent option 0, as detailed in
. You can configure your Controller to one of the other venting options provided you can send commands via
the Serial Interface or you have access to an Edwards TIC Turbo and Instrument Controller or Turbo Controller.
The Controller only energises (‘shuts’) the TAV solenoid valve when it receives a Start command. Prior to that, the
valve will be in the ‘open’ vent state. If you have a large vacuum system, you may wish to allow the backing-pump
to reduce the pressure in the system to an acceptable level before starting the nEXT pump. In this case, you can send
a command via the Serial Interface to close the vent valve before you send a Start command - this is known as a
delayed start.
If you are controlling your nEXT pump with an Edwards TIC Turbo and Instrument Controller or TIC Turbo Controller,
you can drive your TAV solenoid valve from the TIC. Refer to the TIC Instruction Manuals for more information.
Table 20 - Vent options
Option number
Description of vent function
0
Vent valve opens fully below 50% full rotational speed for either Stop command or
Fail.
Note:
This is the factory default setting.
1
Controlled venting from 100% to 50% full rotational speed; vent valve opens fully
below 50% for either Stop command or Fail.
2
Vent valve fully opens immediately Stop command is received; vent valve opens
fully below 50% full rotational speed if Fail.
3
Vent valve fully opens immediately Stop command is received; controlled venting
from 100% to 50% full rotational speed if Fail then vent valve opens fully below
50%.
4
Vent valve fully opens immediately if Fail; vent valve opens fully below 50% full
rotational speed if Stop.
5
Vent valve fully opens immediately if Fail; controlled venting from 100% to 50% full
rotational speed if Stop command received then vent valve opens fully below 50%.
6.7
Vent valve fully opens immediately for either Stop command or Fail.
Summary of Contents for nEXT240
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