Thermo Scientific FOCUS GC, Instruction Manual

Page: 296 / 356

Chapter 15
Maintenance and Troubleshooting
FID Troubleshooting
296 Instruction Manual
NOTE Generally the air flow rate must be set to about 10 times the hydrogen flow rate to keep the
flame lit.
For high sensitivity applications, it is essential that you exclude all traces of
organic contamination from the chromatographic system and/or from the gas lines
of the detector. Such contamination would cause ghost peaks in the chromatogram
or, more commonly, an unstable baseline.
WARNING! It is the customer’s responsibility to ensure compliance with all local safety
regulations concerning gas supplies.
Hydrogen is a potentially dangerous gas. Mixed with air it may give rise to an
explosive mixture. The use of hydrogen requires the operator’s extreme caution due
to the risks involved. For further details concerning hydrogen, please refer to
Using
Hydrogen on page xxiii.
Flame Ignition
You can ignite the flame as soon as the detector temperature has reached 150 °C.
After the flame appears to have ignited, check for water vapor condensed on a
mirror or on the polished end of a wrench directly over the FID exit. You should
observe steam condensing on the cold surface. If not, the flame is not ignited.
WARNING! Do not lean over the FID to see the flame, it is invisible.
Table 15-4 reports the possible causes of flame ignition problems and the relevant
remedies.
.
Table 15-4. Difficulty in Igniting the Flame
Cause Remedy
Incorrect fuel
gas flows Make sure that all flows are correct.
Defective igniter
Check the igniter element. Refer to the Replace the FID
Ignition Assembly Operating Sequence on page 292 for
instructions.