Technical data

5.5.7. Delta t freezing/drying
Preselection of the maximum admissible difference between the
shelf temperature and the product temperature at the end of a
section. The unit only switches to the next process phase if the
actual difference is below the set value.
If, for example, the shelf temperature during the freezing process
is set to -40°C and a product temperature of at least -30°C has to
be ensured before the “main drying” process can start, the
admissible difference is +10K. In this case, enter “10” for the set
value for delta t freezing.
If, for example, the shelf temperature during the drying process is
set to +20°C and a product temperature of at least +15°C has to
be ensured before the “final drying” process can start, the
admissible difference is 5K.
If the difference is not reached within the preset section time, the
section will continue until either the value is reached or the value
falls below or exceeds the set value. A corresponding message is
displayed in the process and equipment information system.
The temperature difference can be set in a range between 1 and
25. In order to ensure the beginning of the next process step,
select a temperature difference that is not too small.
“delta t freezing” is measured by the temperature sensor “actual
value product 1“. If the measurement is not desired or if it is not
possible to use any product sensors, the measurement can be
deactivated by selecting “OFF“ as the set value.
5.5.8. Pressure increase measurement during drying
In the program mode, the pressure increase measurement is
always performed in the last drying phase (main drying or final
drying). The next phase only starts after two successful pressure
increase measurements in a row. In case there are no two
successful measurements at the end of the section, a message is
displayed in the process and equipment information system. The
section is extended until two measurements are performed
successfully.
Adapt the following parameters for the pressure increase
measurement:
Max. Pres. Increase
The maximum admissible pressure increase for a successful
measurement. The value is converted to K in accordance with the
vapor pressure curve above ice.
Start pres. inc. test
Start of the first pressure increase measurement since the
beginning of the last drying section.
Time between tests
Time difference between two pressure increase measurements.
62 • LSC Control System Operating Manual Freeze Dryer ALPHA 1-4 LSC / ALPHA 2-4 LSC