(Standard TCD detector block access continued)
4. Cut the fiberglass tape wrapped around the detector block and peel it off. Unwrap and remove the
heater rope from the detector block (it is probably affixed to the thermocouple wires with more
fiberglass tape).
5. Disconnect the thermocouple by loosening the small philips head screw which holds it on the
detector block clamshell. Next, remove the clamshell by unscrewing the two small philips head screws
that hold its halves together. Gently remove the white insulation to reveal the detector block.
6. The TCD filaments are secured in the detector block by two plates, each of which is held in place
with three hexagonal head screws. Holding the detector block with one hand, use an Allen wrench to
unscrew and remove the hexagonal head screws from one of the filament securing plates. Then, slide
the filament securing plate off the filaments and leads. Set it securely aside.
7. Once the securing plate is removed, the filament and rubber O-ring that seals it can be gently pulled
out of the detector block cell. When replacing a filament, its rubber O-ring should also be replaced.
Check the lip of the detector block cell for fragments of the old O-ring and if any are present, remove
them as they will interfere with proper sealing of the cell. If you’re replacing one reference or sample
filament, replace the other at the same time. If you didn’t have fun disassembling the TCD detector
block, replace all the filaments while you have it open. It’s a good idea to remove then replace one
plate and corresponding pair of
filaments at a time to avoid mixing up
their connections.
8. To install a new filament, color-
code it the same as the filament you
are replacing, then slide it, leads first,
through the appropriate hole in the
filament securing plate. An existing or
replacement filament should occupy
the other hole. Place a new rubber
O-ring against the rim of the detector
block cell which will accept the new
filament. Place filament securing plate
and filaments against the detector block
with the filaments inside the detector
block cells. Replace and tighten the 3
hex-head screws. Repeat this process
on other side to replace the
corresponding filament.
9. Reverse your steps for TCD
detector reassembly. Steps 7-10 of
the high temperature TCD detector
block access instructions detail
reassembly of the inner clamshell and
outer detector housing.
Filament securing plate
Filament
Sample cell
Reference cell
Detector block
Rubber O-rings
Hexagonal head
screws
Insulated filament leads
Exploded view of the standard TCD detector block
Replacing the TCD Filaments continued
DETECTORS
Thermal Conductivity Detector - TCD
