Manual

Operating Manual Freeze Dryer ALPHA 1-4 LDplus / ALPHA 2-4 LDplus General Information on Freeze-drying  19
Possible water residue must be removed from the ice condenser
chamber. The drain valve is closed.
The ground-in stopper of the drying chamber must be greased with
high-vacuum grease!
The layer thickness of the product should not exceed 1 to 2 cm as
otherwise this has a negative effect on the duration of the drying
process.
2.4. Main Drying
The vacuum pump is switched on.
Please note:
Defrosting during the drying process is possible (visible foaming)
when drying products containing e. g. solvents or high salt
concentrations. In this case it is necessary to freeze the product at
temperatures as low as possible, e.g. in liquid nitrogen.
Warning:
Acidic products or products with a high solvent concentration
cannot be dried without special safety measures and devices e.g.
an additional LN
2
cooling trap for protection of the vacuum pump (if
necessary contact our company). Another possibility is to use
chemical resistant vacuum hybrid pumps (e.g. RC-5).
Special precautions are necessary when using azides
because a dangerous explosive develops in combination with
copper or non-ferrous metals! It is absolutely essential to consult
our company!
As soon as sublimation of the water vapour from the frozen product
begins, heat is extracted and consequently the product continues to
cool down.
The maximum rate of sublimation is reached at the start of the
drying process.
Depending on the rate of sublimation the ice condenser
temperature and thus the pressure in the drying chamber
respectively ice condenser chamber rises.
The duration of the main drying phase depends mainly on:
 the layer thickness of the product,
 the solid content of the product,
 the heat supplied to the product during the drying
process,
 the pressure inside the drying chamber during the drying
process.