VICI D-2-IM - Manual (Page 16)

12
Gas Connections
Remember these three points discussed earlier: (1) all surfaces that contact the
gas stream must be glass or stainless steel; (2) do not use copper tubing or brass
fittings; and (3) all tubes must be thoroughly cleaned and baked before use. The
installation instructions below assume that the detector discharge will be supplied
from a nearby cylinder of helium of the proper purity. If your installation is differ-
ent, you may need to modify the instructions appropriately. A number of Valco
fittings have been supplied in the fittings kit to handle different situations.
Figure 3 illustrates gas connections for a typical PD-D2-IM detector system.
Since the distance from the helium supply to the GC varies from installation to
installation, we do not supply tubing to go from that point to the GC.
Installation
Figure 3: Gas connections for a PD-D2-IM system
Installing and Purging the Gas Regulator
1. Make sure the on/off valve on the helium cylinder is completely closed. Screw
the CGA fitting nut of the regulator into the helium 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 reduc-
tion 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. Close the valve
and observe the needle of the high pressure gauge for 15 minutes. If it doesn’t
move, there is no critical leak on the high pressure side of the regulator.
GAS CHROMATOGRAPH
COLUMN INJECTOR
TEE
(ZT1)
HELIUM
PURIFIER
DISCHARGE GAS
(99.999% He)
TGA-R-10F60P
RESTRICTOR
(10 mL/min minimum)
DISCHARGE GAS
INLET
COLUMN
INLET
VENT