Specifications

Operating Manual Freeze Dryer ALPHA 1-4 LD-2 / 2-4 LD-2, Version 0203, Page 29
4.1 Freezing
The freezing of small quantities of product is carried out inside the ice condenser
chamber of the ALPHA 1-4 LD-2 / ALPHA 2-4 LD-2. Larger quantities are pre-frozen
in a deep-freeze.
If liquids are to be dried in bottles with a layer thickness of more than 1 cm we
recommend that pre-freezing is carried out with a shell or spin-freezing-device in a
cooling bath (see previous picture). Due to the centrifugal force the liquid to be frozen
will rise on the wall of the bottle and freeze. With this freezing process the layer
thickness is reduced and thus the total drying period is shortened considerably.
Freezing inside the unit is not necessary if the product is pre-frozen or stored in e. g. a
deep-freeze. In this case, especially when freeze drying small quantities, it is advisable
to pre-cool the shelves in order to avoid partial thawing during the evacuation.
Possible water residue must be removed from the ice condenser chamber. The
defrosting water valve is closed.
The ground-in stopper of the acrylic chamber must be greased with high-
vacuum grease!
The layer thickness of the product should not exceed 1 - 2 cm as otherwise this has a
negative effect on the duration of the drying process.
The process steps of freeze drying
Prefreezing + Drying
under atmosphere pressure
(e.g. at - 25°C)
= formation of the ice structure
under vacuum
(e.g. at 0.1 mbar, equal to -42°C)
= keeps the water contents in the phase
Additionally necessary:
Energy input (= heat)
but: the material remains in the solid/ice phase!
(physical law: the vacuum is responsible
for the product-/steam temperature)