Operation: when the 6870 Freezer/Mill is set up for the first run of the day, with a loaded vial in the coil, make sure the LN valve on the supply tank or line is open. Go to the STATUS screen and touch RUN. The Auto-Fill valve will open and let LN into the Freezer/Mill tub. The valve may close and open several times before the tub is full and Pre-Cool timing starts, but this is normal. LN boils and splashes as it enters the tub and this may temporarily “fool” the upper LN sensor. However, the Auto-Fill System has a built-in pause for the LN to stabilize before measuring the LN level again. Pre-cool countdown will not begin until the tub is full of LN.
During a long run, if the lower LN sensor detects a low LN level, the LN valve will open during a re-cooling period. Again, the valve may open and close several times while the tub is filling, but during “Auto-Filling” the timer stops, and will not start again until the tub is full.
At the end of a run the LN level in the tub may seem low, but this is only because the lower LN sensor has not triggered the Auto-Fill System to fill the tub with LN.
The 6820 Auto-Fill System has been designed to work with typical grinding programs that involve a pre-cooling period and repeated short grinding and re-cooling periods. If you want to use the 6870 Freezer/Mill in a different way – for example, by having a single long period of continuous grinding – please call us first to make sure your plans and the Freezer/Mill are compatible. The lower LN sensor will not trigger the Auto-Fill System to add LN during a grinding period, just during pre-cooling before grinding, and during the re-cooling periods between grinding periods.
6.6 Optional 6814 AutoExtractor (see our catalog or website, www.spexcsp.com)
The 6814 AutoExtractor is a motorized electrical accessory for quick and safe removal of end- plugs from Freezer/Mill vials. It can open both Large-size and Small-size vials but cannot be adapted for Mid-Size Freezer/Mill vials or individual 6753V Microvials. Out of the box, the AutoExtractor is set up for Large vials, but it includes an easily installed insert for handling Small vials.
AutoExtractor operation is a motorized version of the manual 6804 and 6754 Extractors. The end-plug of a chilled vial is placed in the bell of the extractor, with the locating pins lined up with slots in the bell. Then a rocker switch is pressed up to start the extractor screw, which winches out the end-plug. When the vial is opened, pressing the rocker switch down and reversing the screw can retrieve the end-plug. The 6814 AutoExtractor takes the “wrist work” out of opening Freezer/Mill vials and is recommended for labs with high sample throughput.
6.7 Maintenance
The 6870 Freezer/Mill has been designed to provide trouble-free operation over a long period of time. To assure proper performance, perhaps the most important factor is cleanliness. When the unit is at room temperature, any spilled powders or liquids should be wiped up immediately. The internal tub should be wiped clean with a damp cotton cloth after every use. This should prevent the buildup of any powders, mold/mildew, or unsightly gunk over the life of the unit.
If you have spilled any sample powder or liquid inside the unit during a sample run, wait until you are no longer going to continue using the unit, and the mill has warmed up to room
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