11
CAUTION: Do not mount the detector near the column
oven cool-down vents.
Horizontal Mounting
Some older GCs have access to the column oven through the side of the GC.
This does not present a problem as far as operation of the TCD-3 is concerned.
Drill a hole at the appropriate location, orient the detector for convenient
connection, and mark the position of the mounting holes. Drill the mounting
holes and secure the detector to the side of the GC with four sheet metal screws
(not supplied).
Gas Connections
When making gas connections, remember these three points:
• All surfaces that contact the gas stream must be glass or stainless steel
• Do not use copper tubing or brass fittings
• All tubes must be thoroughly cleaned and baked before use.
The instructions below assume that the detector carrier will be supplied from
a nearby cylinder. Since the distance from the carrier supply to the GC will vary
from installation to installation, tubing is not supplied for the supply-to-GC
connection. Consult the VICI catalog or vici.com for any fittings and tubing
required.
The figures on the next page illustrate gas connections for a typical TCD-3
detector system in unreferenced (
Figure 6
) and referenced (
Figure 7
) modes.
Installing and Purging the Gas Regulator
1. Make sure the on/off valve on the carrier gas cylinder is completely closed.
Screw the CGA fitting nut of the regulator into the gas cylinder. Go beyond
finger-tight, but do not tighten the nut all the way – some leakage is required
for the purging operation.
2. Turn the output pressure regulating knob completely counterclockwise.
3. Open the cylinder on/off valve slightly and quickly close it again.
4. Adjust the tightness of the regulator connecting nut to allow a pressure
reduction of ~690 kPa/sec (100 psi/sec). With a new bottle, the gauge should
start out at about 14 MPa (2000 psi).
5. When the pressure drops into the 1.4 - 3.4 MPa (200 - 500 psi) range, open the
cylinder on/off valve slightly and quickly close it again.
6. Repeat Step 5 eight or ten times to be certain that all the air is purged. On the
final purge, tighten the regulator connecting nut very securely as the pressure
approaches the 2.1 - 3.4 MPa (300 - 500 psi) range.
7. Open the cylinder valve to pressurize the regulator once again, then close it
and observe the high pressure gauge needle for 15 minutes. If it doesn’t move,
there is no critical leak on the high pressure side of the regulator.
Installation
