Checking The Liquid Nitrogen Level; Cg-450 Auto Fill System; Description - Cole Parmer Freezer/Mill CG-400 Operation Manual

CG-400/CG-450 Freezer/Mill
6.5 Opening, Emptying, and Cleaning Freezer/Mill Vials (Cont'd)
The steel parts of the chromium-free 6771, 6871, and 6883 vials can also be washed, disinfected,
or autoclaved. Do not wash with bleach or chemical cleaners. Chromium-free steel is not rust-
resistant and must always be dried immediately after washing. Store Cr-Free Vial parts in a
sealed bag with a desiccant.
Rust on steel Freezer/Mill parts can be removed by scrubbing them with steel wool or an abrasive
cleanser. If rusting persists, store the parts in a sealed bag with a desiccant.
6.6 Checking the Liquid Nitrogen Level in the CG-400
The LN should be topped off when needed as a matter of routine. If the programmed grinding
cycle includes more than twenty or thirty minutes of actual grinding time, the nitrogen level
should be visually checked at about that point and more added if needed. A cumulative grinding
time of more than thirty minutes per run is not recommended, as after that much grinding the LN
level is close to the point where the LN sensor will shut down the mill. However, if the mill must
be run for an extended time, and the LN sensor stops the grinding program, the mill can be
refilled with LN and the grinding program resumed where it stopped.

7.0 CG-450 AUTO FILL SYSTEM

7.1 Description

The CG-450 Auto Fill System automatically transfers liquid nitrogen (LN) to the CG-450
Freezer/Mill during operation, making hand-filling unnecessary. The Auto Fill mechanism
includes a cryogenic valve linked to LN sensors in the tub. When the LN level is low, the valve
opens during Precool or cooling stages to let LN into the tub. The Auto Fill System as supplied
also includes a safety valve for the LN transfer hose.
LN transfer hoses can vary with the LN supply tank or line and are therefore not included with the
CG-450 Auto Fill System. Four-foot and six-foot transfer hoses of standard design (part numbers
6906 and 6907) can be purchased from Cole-Parmer, or custom transfer hoses can be designed
and supplied by the user. The LN inlet is a male ½ inch JIC fitting placed low on the right side of
the Freezer/Mill, so the outlet of the hose requires a female CGA295 fitting. The 160 liter and
240 liter LN tanks used by many of our customers generally have a male 3/8 inch (9.5 mm) NPT
outlet, Cole-Parmer transfer hoses come with a matching female 3/8 inch NPT fitting. Excessively
long transfer hoses are not recommended.
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