Martin-christ Beta 2-8 LDplus User Manual download pdf (Page 21)

Operating Manual Freeze Dryer BETA 1-8 LDplus / BETA 2-8 LDplus General Information on Freeze-drying  21

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 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.

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Martin-christ Beta 2-8 LDplus User Manual Page 21