20 • Description of the Freeze Drying Processes Operating Manual Freeze Dryer ALPHA 1-2 LDplus
The rack is set onto the base plate. With small samples it is
recommended to pre-cool the shelves. In this way, a partial
thawing during the evacuation process is avoided.
When freezing and drying is performed separately outside the ice
condenser chamber it is directly started with the main drying
process.
As soon as the shelves with the frozen samples have been put in,
the unit and the drying chamber are sealed and the process is
started. To do so, the main drying process has to be activated in
the control system so that the pressure control valve opens and
the main drying process starts (see chapter 5.6).
3.2. Separate Freezing and Drying Outside the Ice
Condenser Chamber (Process B) with Sealing
Device
Possible water residue is removed from the ice condenser
chamber. The drain valve is opened so that the water residue can
drain off. The ice condenser chamber should be wiped out if
necessary.
The refrigeration compressor and the vacuum pump are activated
via the control system to start the pre-freezing of the ice condenser
and the warming-up of the vacuum pump. The valve is closed
during warming-up of the pump. In case the unit is not equipped
with an electromagnetic pressure control valve we recommend to
use a manual stop valve. Without such a valve the vacuum pump
must not be warmed up.
The rack is set onto the base plate. With small samples it is
recommended to pre-cool the shelves. In this way, a partial
thawing during the evacuation process is avoided.
The sealing device is used to seal injection bottles under vacuum
or inert gas with ribbed rubber stoppers. Depending on the type of
sealing device the bottles are sealed on 1 to 2 shelves. To do this,
the shelves are moved against each other by a pressure plate
using a spindle.
The height of the pressure plate must be adjusted according to the
height of the bottles. To do so the threaded pin for height
adjustment is removed. The threaded rod is screwed into the lower
shelf until its slotted head is on the same height as the rack (upper
edge).
Then the pressure plate is fastened with the threaded pin in such a
way that it will rest on or slightly above the rubber stopper. When
using two or more shelves every shelf is set directly on or with a
slight distance to the rubber stoppers as it is the case for the
pressure plate.
Instead of the stopper the vacuum-tight rotary leadthrough is put
into the standard ground socket of the drying chamber. Before
inserting, the ground-in surface of the leadthrough is greased with
vacuum grease.
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