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VDL (E3.1) 10/2020 Page 22/196
If the following precautions are not followed, the vapors resulting from heating of the solvent can ignite on
the hot walls of the inner chamber
Required measures for operation with solvent-containing materials that can form an ex-
plosive mixture with air:
• Sweep the area for electrical equipment, preheating chamber and controller housing
for a
defined time (chap. 9.3.2) prior to start-up with compressed air with maximum overpressure.
Subsequent sweeping of the area for electrical equipment, preheating chamber and control-
ler housing with an overpressure of at least 25 Pa (recommendation: >40 Pa) must take
place during the entire operating cycle
and must be monitored at the manometer on the
chamber front. In addition, monitoring of the defined inlet pressure (2 bar) of the compressed
air sweeping is required.
• Only after completing the defined sweeping time, put the chamber in operation.
• Take the auto-ignition temperature
from the safety specifications of the solvent. In the case
of solvent mixtures, use the auto-ignition temperature of the material with the lowest auto-
ignition temperature. Make sure that the auto-ignition temperature is above 200 °C.
• Enter the temperature set-point (drying temperature) on the controller.
• Set the safety controller (temperature limiter class 2). Recommended setting: safety control-
ler mode “Limit”, safety controller value approx. 5 °C above the set-point.
• During the drying process, use only those solvents for which the auto-ignition temperature
has been entered.
• Make sure that the technical ventilation is active. Make sure that the compressed air sweep-
ing is active and that the defined inlet pressure is monitored. Bring in the material to be dried.
• Start the drying process. The heating unit is only released when a pressure threshold of
100 mbar is reached.
• Make sure that sweeping the area for electrical equipment, preheating chamber and control-
ler housing with at least 25 Pa overpressure (see manometer display) takes place during the
entire operating cycle. Recommended value: >40 Pa.
• The duration of the drying process can be determined by means of the pressure display on
the controller. When the pressure drops to the set-point, the drying process is finished.
• Make sure that the technical ventilation is active. Make sure that the compressed air sweep-
ing is active and that the defined inlet pressure is monitored.
After termination of the drying
process, ventilate the vacuum drying oven with ambient air or inert gas.
Unload the loading
material and turn off the oven.
• Sweep the area for electrical equipment, the preheating chamber, and the controller housing
(triangular instrument box) at least 10 minutes with compressed air (recommended).
• Make sure that the technical ventilation is active when emptying the condensate catchpot of
the vacuum pump.
• Make sure that sweeping the area for electrical equipment, preheating chamber and control-
ler housing with at least 25 Pa overpressure (see manometer display) is active when empty-
ing the condensate catchpot of the vacuum pump. Recommended value: >40 Pa.
• Before starting a new drying process with a different solvent, check again the auto-ignition
temperature
at the safety specifications of the solvent. In the case of solvent mixtures, use
the auto-ignition temperature of the material with the lowest auto-ignition temperature. Make
sure that the auto-ignition temperature is above 200 °C.
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