Main Drying - Fisher ALPHA 1-2 LDplus Operating Manual

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 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 cooling trap for protection of the vacuum pump (if
2
necessary contact our company). Another possibility is to use
chemical resistant vacuum hybrid pumps (e.g. RC-5).
General Information on Freeze Drying • 13
Operating Manual Freeze Dryer ALPHA 1-2 LDplus