Agilent Technologies X3500-64000 Mode D'emploi page 281

Vent Accessories
The vent valve and vent device allow to avoid undesired venting of
the pump during temporary power failure and enables an automatic
vent operation.
TwisTorr 304 FS on board controller compatible
Vent Valve mod. 9699834
Figure 44
This vent valve waits before opening a minimum time of about 5 sec.
This time can be increased up to about 220 min. by means of a setting
of the controller software (optional).
To install the vent valve, unscrew the threaded plug (see figure
below).
TwisTorr 304 FS User Manual / 87-901-027-01(B)
Technical Information
Vent Accessories
281/304
17