Troubleshooting
6850
6850
Released: April 2004 6850 Series Gas Chromatograph Service Procedures 308
Table 1-1. Low FID flow rates
An electronic leak detector is very useful for
determining if the column fitting is leaking. If a
leak is suspect, replace the column ferrule and
the capillary adapter fitting ferrule if installed.
When reinstalling the capillary column, remember
to withdraw the column 1 to 2 mm from the tip
of the jet to avoid possible restriction to H
2
and
makeup flow.
The Control Module for the 6850 GC has a built
in diagnostic to determine if the jet is plugged
called the "Jet Test." If any or all of the gas
flows are low, there could also be leak(s) at the
EPC gang fitting. In this case, replace the O-rings
and tighten if necessary (10-mm screws, part
number 0515-2495).
If any of the measured flow rates are incorrect,
there is always the possibility that the EPC
module is out of calibration or defective.
All of the flows could measure correctly and the
FID jet seal could be leaking.
If there is an imperfection in the seal, H
2
will
leak around the jet rather than going through.
Reason Solution
Leak at column fitting
Replace column adapter, column ferrules
Plugged or partially
plugged jet
Clean or replace. To clean, use a .011-inch or
.018-inch wire to clean the jet. Sonicate the
jet in a solvent appropriate to the application.
Loose or missing
gasket at base of FID
Replace
Sealing surface
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