Varian 450-GC, User Manual

Page: 135 / 205

Flame Ionization Detector (FID) - Detectors
Varian, Inc. User Manual 450-GC Page: 285
4. If detector EFC is present, set the following flow rates in the adjustments
section of the FID method:
•
Make-up flow to 25 mL/min.
•
The hydrogen flow to 30 mL/min.
•
Air flow to 300 mL/min.
Note: For optimum performance the combined make-up flow
should be 30 mL/min, so some adjustment of the make-up flow may be
necessary.
5. If manual pneumatics is installed, attach a bubble or digital flowmeter
(AL5700) to the top of the FID tower using the adapters supplied in the FID
accessory kit (Note that the most reliable measure of flow is directly from
the flame tip. This prevents wrong-adjustment due to leaks in the overall
tower assembly). Check the following flow rates and set them if necessary:
combined carrier gas + make-up flow to 30 mL/min, the hydrogen flow to 30
mL/min and the air flow to 300 mL/min.
6. Press the DETECTOR key on the 450-GC Display/Keyboard, select
the FID by its location and turn on the FID oven power. Set the oven
temperature to 300 °C. Verify that the FID electronics is turned OFF.
Operation
1. Check the detector temperature status on the DETECTOR/FID screen.
Check the FID range setting and set to range 12, if necessary.
Generally, to prevent water condensation in the detector assembly, the
detector should be operated at a temperature above the column
temperature and not b elow 150 °C. If the detector is o perated at a lower
temperature, condensation can lead to excessive noise.
2. After the FID oven has reached its setpoint temperature, turn on the FID
electronics. Note that the FID will ignite automatically when auto-ignite
conditions are fulfilled (for detailed information about auto-ignite conditions
see here, on page 287). The 450-GC monitors the FID background current
continuously and will attempt to ignite the flame (only if in Setup/Detector
the checkbox on page 75 “check for flame out” is checked) if the current
drops below a specified threshold. Up to three attempts to ignite the flame
will be made before the 450-GC reports a flame-out fault. If a flame-out fault
is reported, correct the cause of the flame-out and then clear the fault in
Instruments Log.
The FID will automatically ignite after the fault is cleared.