Lighting The Fpd Flame - Agilent Technologies 7820A Advanced User's Manual

Lighting the FPD flame

Advanced User Guide
Table 21 Recommended flows (continued)
Detector gases
Hydrogen
Air
Carrier + makeup
Helium, either as carrier or makeup gas, may cool the detector
gases below the ignition temperature. We recommend using
nitrogen rather than helium.
Before trying to light the flame, have the detector at operating
temperature. Removing the condensate tubing may help, but be
sure to replace it before making runs.
It is difficult to light the flame with the flows shown in
particularly in the sulfur mode. If the flame will not light with
the sulfur mode flows shown, change to the phosphorus mode
flows. After ignition, gradually reduce the flows to the sulfur
values. Some experimentation will be needed.
When either of the flame ignition methods in this section is
used, the FPD automatically performs this sequence:
Turns all detector gases—air, hydrogen, makeup—off. Carrier
1
remains on.
Sets air flow to 200 mL/min.
2
Turns the glow plug ignitor on.
3
Ramps the hydrogen flow from 10 to 70 mL/min.
4
5 Resets the air flow to the air flow setpoint.
6 Resets the hydrogen flow to the hydrogen flow setpoint.
7 Turns the makeup gas on.
Compares the signal change with the Lit offset value. If the
8
change is greater than Lit offset, declares the flame on (lit). If
it is less, declares the flame off (not lit).
For this process to work, there must be enough air pressure to
the pneumatics module to provide 200 mL/min flow. We
recommend a supply pressure of 90 psi.
Sulfur mode flows, Phosphorus mode
mL/min flows, mL/min
50 75
60 100
60 60
5
Detectors
Table 20,
105