Freeze Dry Company in based in central Minnesota.
Freeze Dry Company - Equipment, Opportunities, Training, PO Box 570 Nisswa Minnesota 56468 - 1-800-851-2110
Freeze Dry Company

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Freeze Drying Machines

The success of the freeze-dry process and the future of freeze-dry technology depend in large part on the skill of the practitioner and the dependability of the freeze-dry machine to get the job done right - for whatever application it is used. It is the responsibility of the freeze-dry practitioner to have the required skill to use the process successfully, but it is the responsibility of the manufacturer to build a machine that will incorporate dependability and efficiency.

Proper engineering and high quality construction must be present in a machine if it is to operate continuously, day after day for long periods of time. With these criteria in mind, Freeze Dry World reviewed the L-3666 "Production" model built by Northern Freeze Dry  Manufacturing of Pequot Lakes, Minnesota. the l-3666 derives its model number from its specimen chamber dimensions - 36" in diameter, 66" in length.

Northstars Workhorse with a Proven Track Record
From the standpoint of appearance, the freeze dry machine L-3666 is attractive, sturdy, and business like. the wood-grain panels contrast nicely with the bright blue metal work. The units physical design is neat and compact. All components, including the condenser tank fit snugly inside the frame, which supports the specimen chamber.
All control switches and gauges, including the specimen chamber thermostat and vacuum release lever, are clustered neatly at the front of the freeze dry machine, allowing operation of the machine from one position. The main control switches serve power to the condenser refrigeration compressor, vacuum pump, and interior light. to the left of the switches is a dial timer that activates the defrost cycle for the condenser temperatures of both condenser and specimen chamber are read on a LED electronic digital gauge with a dual position switch. The electronic vacuum gauge measures atmospheric pressure within the vacuum system in microns (normal atmospheric pressure is a approximately fifteen pounds per square inch, which equals 760,000 microns. The sublimation process begins at 675 microns with the specimen chamber at -5 degrees F). The L-3666 is designed to draw down to 25 microns or less (empty unit). At this pressure, more than 99.9 percent of the air has been removed from the specimen and condenser chambers. The vacuum system must be absolutely leak-proof and strongly built in order to maintain these vacuum levels.
Norhtstar has developed a door system that allows full view of the inside of the specimen chamber while at the same time ensures an airtight seal. A heavy steel ring is welded to the end rim of the freeze dry machine chamber, it's exposed edge is sanded smooth, then covered with a thin coat of vacuum grease. A heavy duty rubber gasket is then capped over the ring. The front edge of the gasket is also coated with vacuum grease. a massive Plexiglas door, held by a sturdy hinge system, is then pressed against the gasket for a few seconds after the vacuum pump is turned on to seal the chamber. This same closure system of Plexiglas door against gasket is used on the condenser chamber door as well, but on a smaller scale.
Freeze Dry Machine Vacuum and Refrigeration
 
The vacuum for both the specimen and condenser chambers is achieved by one pump; a 1-1/2 horsepower motor that evacuates at the rate of 26.8 cubic feet per minute. Since the condenser and specimen chamber are on the same line, they draw down simultaneously.
 
The specimen chamber and condenser each have their own refrigeration system, which allows temperature in the condenser to reach -55 degrees F or colder, while the specimen chamber is thermostatically-controlled for a range of temperatures compatible with particular freeze-dry processes. The temperature difference between specimen chamber and condenser sets up the condition whereby moisture in the form of vapor is drawn out of the specimen chamber and collects as frost on the colder condenser wall, a phenomenon similar to water condensing out of warm air and collecting as water on the side of an iced drink glass on a summer day. However, in the case of the freeze-dry machine, the moisture that originates in the specimen never takes the form of water. It passes from the ice crystal state to a vapor and then back into frost.
 
When enough moisture is withdrawn from the specimen chamber to accumulate 1" to 2" of ice in the condenser chamber, the defrost cycle is begun. The L-3666 employs a quick and efficient hot-gas defrost system. Within approximately 15 minutes from the beginning of the defrost cycle, the condenser wall is warm enough to produce a layer of water between the wall and the accumulated cylinder of ice, which can then be extracted and discarded.
 
A Little Ummph
 
The machine gets its "Production" name for its 37.5 cubic feet of freeze-drying capabilities. It has been used by taxidermists for freeze-drying a wide variety specimens, from insects and small rodents up to life size bears. Although it is a fairly large machine, it can be moved around on level floors quite easily on its casters-with a little extra ummph.
 
Maintenance
 
Maintenance of the freeze dry machine, as covered in its operating manual, consists mainly of changing oil in the vacuum pump and keeping the refrigeration coils clean. The manual also covers freeze dry basic theory; features of the machine; set-up, start-up, shutdown, and defrost procedures; and troubleshooting.
The L-3666 "Production" has evolved into being Northstar's most popular unit over the years, and it appears that it will continue as the workhorse of the Northstar line.


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Freeze Dry Company Inc.
P.O. Box 570 Nisswa, Minnesota 56468
Phone 218-963-2100    Toll Free 800-851-2110    Fax 218-963-0761

2006 Freeze Dry Co.
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