56 • Maintenance Operating Manual Freeze Dryer ALPHA 1-2 LDplus
valve with warm water (max. +50°C). Finally it is necessary to wipe
the ice condenser chamber dry.
It is n o t
recommended to defrost the unit simply by leaving it at
room temperature over a long period of time. In this case the
tungsten wire reacts with the ambient atmosphere!
After defrosting and drying the unit, it is additionally recommended
to evacuate the unit for 30 minutes with o p e n
gas ballast valve.
All residues that may harm the tungsten wire are removed in this
way.
7.3.2. Replacement and adjustment
The vacuum sensor has to be replaced if “---“ is shown in the
vacuum field after the aeration of the system instead of “Atm” and
if the process and equipment information window shows the
message “Vacuum sensor defective”. If after the warm-up phase
and the aeration of the unit the vacuum display still does not show
“Atm” but a value equal to or smaller than 900 mbar, the vacuum
sensor has to be readjusted. The warm-up phase of the vacuum
sensor takes at least 5 minutes.
7.3.2.1. Vacuum sensor adjustment
The vacuum sensor has two adjustment buttons labelled “adj” and
“set”. The buttons are protected by protective caps. Remove the
protective caps of the buttons prior to adjusting the sensor. Use a
small pen (max. ∅ 2.5mm) to actuate the buttons. Refit the
protective caps after the adjustment.
A digital readjustment to atmospheric pressure (Atm) and zero is
possible directly at the vacuum sensor using the button labelled
“adj” (adjust). The measuring transducer automatically recognises
the adjustment point. If a zero adjustment has to be performed, the
actual pressure should be smaller than 5.0x10
-5
mbar (factory
setting). Alternatively, the sensor can also be adjusted to a
reference value (see below). We recommend a warm-up phase of
at least 5 minutes before the adjustment.
Buttons with protective caps
for adjusting the senso
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