Technical data

3.4. Separate freezing and drying of liquids in flasks
(process B)
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 unit and the vacuum pump are activated via the
control system to pre-cool the ice condenser and to warm up the
vacuum pump. The valve is closed during the warm-up of the
vacuum pump. In case the unit is not equipped with an
electromagnetic pressure control valve, we recommend using a
manual stop valve. Without such a valve, the vacuum pump
cannot be warmed up.
Several manifolds and attachable drying chambers with
connections for rubber valves are available for drying outside the
ice condenser chamber (see accessories catalogue). The drying
chamber with connections for rubber valves is mounted directly on
the sealing ring in the base plate. Manifolds with standard ground
joints NS 45/40 are connected via the internal ground-in
connection of the acrylic lid.
In order to ensure a vacuum-tight connection and to simplify the
removal of the accessories, the ground-in surfaces must be slightly
greased with vacuum grease before use. The accessory is then
attached and turned by 360° for an even distribution of the grease.
The ground-in surfaces have to be cleaned and greased before
any further installation of accessories.
Before the drying process can start, it is necessary to check that
all valves are closed.
The main drying process has to be activated in the control system
so that the pressure control valve opens and the main drying
phase starts.
Attention:
The frozen samples can only be connected to the valves when the
pressure has fallen below 1.030 mbar.
Liquids are frozen in flasks according to the shell freezing
principle, by hand or with a rotator. These freezing methods
reduce the layer thickness and thus also the drying time to a
considerable extent.
Most of the available manifolds and valves allow a continuous
connection and removal of flasks during the drying process. Every
connection has a stop valve and an aeration valve.
If the rubber valves or stainless steel valves are stiff, they must be
dismantled, cleaned, slightly greased with vacuum grease and
reassembled.
It is also possible to connect a distributor for 15 ampoules to every
rubber valve.
Operating Manual Freeze Dryer ALPHA 1-4 LSC / ALPHA 2-4 LSC Description of the Freeze Drying Processes • 23