1 Installing the GC
Installation and First Startup 49
Step 17 Connect cryogenic cooling (if present)
Cryogenic cooling allows you to cool the oven or inlet, including cooling to setpoints below
ambient temperature. A solenoid valve controls the flow of coolant to the inlet or oven. The
oven can use either liquid carbon dioxide (CO
2
) or liquid nitrogen (N
2
) as a coolant. All inlets
except the multimode inlet must use the same coolant type as the oven. The multimode inlet
can use a different coolant than configured for the oven, and can also use compressed air as a
coolant.
CO
2
and N
2
coolants require different hardware on the GC. (You can use air cooling on a
multimode inlet, with either the CO
2
or N
2
solenoid valves and hardware.)
Flared or AN tubing fittings are commonly used to connect the liquid supply tubing to the cryo
coolant tank. Check with the supplier of the coolant before plumbing to be sure you have the
correct fittings.
Connecting liquid carbon dioxide
Do not use copper or thin-wall stainless steel tubing! Either presents an explosion hazard.
Do not use padded tanks for CO
2
supplies. The cryogenic valve is not designed to handle the
higher pressures padded tanks generate.
The tank must be equipped with an eductor tube (dip tube) that reaches to the bottom of the
tank, so that liquid (rather than gaseous) CO
2
is drawn.
Materials needed
• 1/8-inch heavy-wall, stainless steel tubing
Procedure
1 Locate the inlet for liquid CO
2
on the rear of the GC. Prepare enough tubing to reach from
the supply tank to this fitting. See Figure 13.
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