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6850 Series GC Site Preparation

GC, GC/MS, and ALS Site Preparation Guide 95

Cryogenic Cooling Requirements

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 and inlet can use liquid carbon

dioxide (CO

) as a coolant.

Using carbon dioxide

Liquid CO

is available in high- pressure tanks containing liquid. The CO

should be free of particulate material, oil, and other contaminants. These

contaminants could clog the expansion orifice or affect the proper

operation of the GC.

Additional requirements for the liquid CO

system include:

• The tank must have an internal dip tube or eductor tube to deliver

liquid CO

instead of gas (see the figure below).

• Typical liquid CO

tank pressure will be 4830 to 6900 kPa (700 to

1,000 psi) at a temperature of 25 °C.

WARNING

Pressurized liquid CO

is a hazardous material. Take precautions to protect

personnel from high pressures and low temperatures. CO

in high concentrations is

toxic to humans; take precautions to prevent hazardous concentrations. Consult

your local supplier for recommended safety precautions and delivery system design.

CAUTION

Liquid CO

should not be used as a coolant for oven temperatures below –40 °C

because the expanding liquid may form solid CO

—dry ice—in the GC oven. If dry ice

builds up in the oven, it can seriously damage the GC.

WARNING

Do not use copper tubing or thin-wall stainless steel tubing with liquid CO

. Both

harden at stress points and may explode.

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Carrier 58GC Specifiche Pagina 95