User guide

118 Advanced User Guide
6 Checking for Leaks
Preparing the GC for Maintenance
Before most maintenance procedures, the GC must be made
ready. The purpose of this preparation is to avoid damage to
both the instrument (electronics, columns, etc.) and the user
(shocks, burns).
Column and oven preparation
The main hazards here are temperature (burns) and column
exposure to air.
• Cool the oven by changing its setpoint to 35 °C. This allows
the oven fan to assist cooling.
• Leave the carrier gas flow On until the oven has cooled. This
protects the column from oxygen damage.
Inlet preparation
We are concerned with the possibility of burns and air intrusion
into the column.
• After the oven and columns have cooled, reduce all inlet
flows to 0.0 and turn the temperatures Off.
• For inlet- only maintenance, leave all detectors at their
normal setpoints except for the TCD filament, which should
be turned Off.
• If the column is to be removed, cap both ends to keep air out.
Detector preparation
This is another burn hazard area, plus the possibility of damage
to the very sensitive electronics.
Some detectors (uECD, FPD, NPD) require 12 hours or longer to
stabilize from the detector- off condition.
• To cool the detector, reduce the temperature setpoint to
35 °C.
• Some detectors (FID, NPD, FPD) use high voltages. The high
voltage supply is part of the electrometer. Turn it Off to
disable the high voltage.
• The filament in the TCD will be damaged if exposed to air
while hot. To protect the filament, turn it Off.