GC Not Ready Symptoms 4
Agilent 7890 Series Troubleshooting 107
• During the ignition sequence, display the air flow rate. The
air flow rate should go to 200 mL/min (7890A) or
400 mL/min (7890B) while trying to ignite to flame. If not,
there is insufficient air supply pressure.
• Check the column and makeup flow rates.
• Ensure that condensation in the vent tube is not dripping
back into the detector. The flexible plastic vent tube must
run from the detector into a container, without sagging, in
order to properly drain water condensate. Keep the open
tube end out of the water in the container.
• Check the Lit offset value. The typical Lit offset value is 2.0. If it
is zero, autoignition is turned off. If it is too large, the
software will not recognize that the flame is lit and will shut
the detector down.
• If the flame still will not light, there could be a large leak in
the system. This results in measured flow rates being
different from actual flow rates, causing non-ideal ignition
conditions. Thoroughly leak check the whole system. (See
Checking for Leaks.)
• Try increasing the supply pressures to the FPD flow module.
This makes the flame easier to light without changing the
setpoints.
• Under some operating conditions, the flame will light more
easily with the vent tube removed. After lighting the flame,
reinstall the vent tube.
• The sulfur mode can be particularly hard to light (FPD only,
not FPD
+
). Try changing to the phosphorus mode flows,
lighting the flame, and gradually alter the flows to the sulfur
values.
• Check cable connections to coupling, coupling connection to
glow plug, tight glow plug.
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