User`s guide

Accessories
190
(140 to180 kPa).
To conserve liquid nitrogen, the accessory will be turned off
automatically under the following conditions:
• when the ATD/TD is in Standby.
• when the trap low temperature is set to -30°C or higher during
Mode 2 (two stage desorption).
• when only trap heating is initiated from Standby. The trap will
heat immediately without first cooling to the trap low
temperature.
NOTE: Subsequent runs will not begin until the trap temperature
has reached its set point.
Once the accessory has been installed and liquid nitrogen is running
through the system, then you must create a new method or revise an
existing method that utilizes the lower temperatures.
There are two drip trays installed with the LN2 accessory, one under
the accessory at the rear of the TD, and another under the trap
enclosure. These trays are used to collect the moisture and direct it
into a runoff tube. These runoff tubes should be placed in or over a
container to collect the moisture and keep it away from the ATD/TD.
This container should be emptied periodically if moisture buildup is
significant.
An insulated feed tube is provided with the LN2 accessory, to
connect the liquid nitrogen supply to the instrument. Use only this,
or similar, tubing. Do not use longer tubing, or cooling capacity may
be impaired. For optimum cooling efficiency, trim the feed tube to
the minimum length required to supply liquid nitrogen to the TD.
Ensure that all bare metal and fittings are covered with the insulation
provided.
WARNIN
G
A pressure relief valve set to 50 psig (350 kPa), should be
installed in the tubing between the Dewar flask and the liq-
uid nitrogen accessory. This will prevent build up of pressure
in the tube should the liquid nitrogen accessory and the
Dewar flask be turned off while liquid nitrogen is still
present in the tubing.