Routine Maintenance: Detectors
Maintaining a thermal conductivity detector (TCD)
Released: March 2004 6850 Series II GC User Information page 184 of 256
Routine Maintenance: Detectors
The procedures described in this section can be performed by the user to
maintain the detectors in the GC. They may involve exposure to heated sur-
faces, but not to hazardous voltages.
Maintaining a thermal conductivity detector (TCD)
If the TCD is displaying problems such as a wandering baseline, increased
noise level, or changes in response on a checkout chromatogram, it is probably
contaminated with deposits from such things as column bleed or dirty samples.
The TCD is cleaned by a process known as thermal cleaning or bakeout.
Perform bakeout only after you have confirmed that the carrier gas and the
flow system components are leak and contaminant free.
TCD plumbing
Figure 31. Internal/External TCD plumbing
Makeup and
reference in
External
pressure
regulator
Filter
frit
Proportional
valves
Pressure
sensors
Restrictors
Reference
switching
valve
Control loops
Makeup flow
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