Chapter 4: Operating Instructions
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The display will show:
At any time the DISPLAY button can be pressed to select a different
function.
Setting the Operating Vacuum Level
The vacuum level may be manually set by the user to optimize the freeze dry
process. Normally, the sublimation rate will increase if there is less vacuum
(a higher pressure) in the Triad Freeze Dry System. A good starting place is
to set the vacuum to a level that will hold the sample temperature
approximately 10°C cooler than the eutectic temperature. Adjustments to the
vacuum level must be made for various freeze drying conditions. Factors that
must be considered are whether the sample is freeze dried on heated shelves
or in glassware attached to manifold valves, the volatility of the sample itself,
the size of the sample and the heat energy supplied to the sample. When the
vacuum control is set to operate at less vacuum, the ice holding capacity of
the collector may be decreased.
Some guidelines for setting the Triad Freeze Dry System are shown below.
These show pre-freezing temperature and vacuum levels. The user of the
specific samples that are being freeze dried must determine exact protocols.
Material
Solidification/Eutectic
Temperature
Pre-Freeze
Temperatures
Vacuum Set Point
Bacteria, Virus
-40°C and Colder
-50°C and Colder
0.404 mBar and Lower
Milk
-5 to -13
-15 to -23
1.65 to 0.77
Fungi
-40 and Colder
-50 and Colder
0.04 and Lower
Vegetable Tissue
-25 to –50
-35 to –60
0.22 to 0.01
Human Tissue
-30 to –40
-40 to –50
0.12 to 1.04
Blood Plasma
-10 to –25
-20 to –35
1.03 to 0.22
Vaccine
-30 to –40
-40 to –50
0.12 to 0.04
VACUUM UNITS:
MBar
Pa
Torr
