TCD Assembly
The equipment images in this document may differ slightly from your equipment, however the instructions are the same unless otherwise noted. |
The filaments in the thermal conductivity detector assembly are heated to high temperatures and may be exposed to corrosive gases, therefore they may eventually need to be replaced. Symptoms that the TCD filaments may need replacing:
- A stable TCD baseline cannot be maintained.
- Data collection results in very high or very low peaks that are inconsistent with previous experience.
- During a data collection, no TCD signal is displayed on the main display or the application indicates that no TCD signal is present.
Contamination of the thermal conductivity detector filaments will produce the symptoms described above. To clean the filaments, set the filament zone to 150 °C and flow an inert gas through the analyzer for several hours. If this action does not correct the problem, replace the TCD assembly.
Replace the TCD assembly
The equipment images in this document may differ slightly from your equipment, however the instructions are the same unless otherwise noted. |
- Ensure that no heat is being applied to the analyzer. If necessary, enable manual control and set the target temperature for the heat zones to ambient. Wait for the analyzer to cool.
- Power OFF the analyzer but do NOT disconnect the power cord from the analyzer.
The power cord must remain connected to maintain an electrical ground connection to the analyzer. |
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Press in on the right side of the retractable handle on the top of the analyzer to protrude the handle. Use the handle to open the hinged top panel. It is not necessary to remove the top panel. Pull down the upper front panel.
- Pull the Bypass/Trap valve cover retaining plungers outward until the Bypass/Trap valve cover is released. Pull the cover up and out.
- Remove the insulation from the rear of the Bypass/Trap valve and locate the TCD assembly (not shown).
The thermal conductivity detector assembly and nearby components may be hot. Allow the TCD to cool before removing it. Use the cotton gloves provided with the analyzer to protect your hands. |
- Loosen all four fittings for the stainless steel tubing. Label each piece of tubing for reconnection.
- Unplug the TCD assembly cable from the card cage motherboard and cut the plastic cable ties that retain the various cables. This frees the cables for removal of the TCD and cable.
- Use a screwdriver to remove the two TCD mounting screws from the yoke plate. Lift the TCD assembly out of the analyzer.
- Install the new TCD assembly in the analyzer. Reconnect the tubing at all four fittings and reconnect the cable to the card cage motherboard.
- Reinstall the insulation in the rear of Bypass/Trap valve over the TCD assembly.
- Reinstall the Bypass/Trap valve cover and allow the retaining plungers to snap into place.
- Close the top panel and the upper front panel.
- Power ON the analyzer.
- Adjust the filament temperature to 150 °C and select an inert carrier gas to flow through the TCD. Set the TCD Zone temperature to 110 °C.
- Allow the TCD baseline to stabilize. Go to Unit [n] > Show Status to observe the TCD reading. Stabilization may take several hours.
Clean the TCD Assembly
In some instances, contamination of the thermal conductivity detector filaments will produce the symptoms described above. To clean the filaments, set the filament zone to 150 °C and flow an inert gas through the analyzer for several hours. Contact your Micromeritics service representative if necessary.
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