Martin-christ Beta 2-8 LDplus User Manual download pdf (Page 24)

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

2.5. Final Drying

The final pressure in the drying chamber depends on the ice

condenser temperature according to the vapour pressure curve

above ice :

e. g. 1.030 mbar correspond to -20°C

0.370 mbar correspond to -30°C

0.120 mbar correspond to -40°C

0.040 mbar correspond to -50°C

0.011 mbar correspond to -60°C

The unit is in operating condition if the temperature of the ice

condenser is lower than -50°C and the pressure is lower than

0.120 mbar.

The final pressure measured by the vacuum sensor when there is

no product in the unit and its corresponding ice temperature value

is mainly determined by the warmest place of the ice on the ice

condenser chamber. Moreover, this value is affected by residues

or parts of solvents in the product with a higher vapour pressure.

2.6. End of Drying and Aeration

A rough indication of the end of drying are the vacuum and the ice

condenser temperature. The ice condenser is no longer loaded

and reaches the final temperature of approx. -55°C to - 85°C. The

pressure in the drying chamber decreases according to the ice

condenser temperature.

The vacuum pump is switched off and the drying chamber is

vented via a rubber valve or the aeration valve on the left side of

the unit. The aeration valve can also be used to “flood” the unit

with nitrogen or another inert gas instead of using air.

CAUTION! Maximum overpressure 0.2 bar!

Then the unit is switched off and the product is removed.

2.7. Defrosting

If the freeze-dryer is not equipped with a defrosting device,

defrosting of the ice condenser is carried out at room temperature

or with warm water. At a maximum the ice condenser chamber

may be half filled with water.

When defrosting the ice condenser with (warm) water, it is of

crucial importance that no water gets into the pipe connection for

the vacuum pump and the vacuum sensor (see figure)!

The condensate as well as the defrosting water are drained

through the drain valve at the left side of the unit. To do this, a

hose is put onto the nozzle. The condensate and the defrosting

water are collected in a vessel.

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Martin-christ Beta 2-8 LDplus User Manual Page 24