VD (E2.1) 10/2011 page 55/83
14.2 Breaking the vacuum (flooding)
When the drying procedure is complete, the vacuum in the inner container is broken (flooded).
• VD 23: open air/gas valve (4)
• VD 53 and VD 115: open aeration valve (5) and fine dosing valve for inert gas (6)
Fresh air is introduced into the lower part of the rear panel of the inner chamber and is evenly distributed
in the inner chamber. This supply of fresh air by under-flooding prevents turbulence of pulverized drying
material.
14.3 Operation with inert gas
When operating the VD vacuum drying oven with inert gas, correctly follow the technical ventilation
measures, as described in the guideline BGI/GUV-I 850-0 on safe working in laboratories (formerly
BGR/GUV-R 120 or ZH 1/119 laboratory guidelines issued by the employers’ liability insurance
association) (for Germany).
WARNING
Release of inert gas.
Danger of poisoning.
Ensure technical ventilation measures.
When decommissioning the VD vacuum drying oven, shut off the inert gas valve (4) or
(6).
Install a pressure reducer for inert gas operation. Set the pressure reducer to a pressure slightly above
ambient pressure. Ensure that the pressure reducer will open. Do not change this setting in order to avoid
perturbation inside the oven and release of big quantities of inert gas after flooding the VD.
Following evacuation, an inert gas, e.g., nitrogen, is led into the inner chamber via the air/gas valve (4)
(VD 23) or the fine dosing valve for inert gas (6) (VD 53, VD 115), until pressure compensation with the
atmosphere occurs. Depending on the individual application, you can perform a second evacuation and
repeat the inert gas flooding.
When the inert gas fine dosing valve is open, a maximum of approx. 0.6 m³/h gas flows into the inner
chamber. The introduction of inert gas by under-flooding in the lower region of the inner chamber rear
wall and the extraction at the inner chamber ceiling allow an effective inert gas flushing.
If the oven is charged to full capacity, depending on the load, deviations from the specified
heating up times may occur.
15. Switching contacts 24V DC via operation lines
Operation lines 1 and 2 are used to switch on and off electrical equipment (nominal voltage 24 V DC,
current consumption max. 0.4 A). The switching contacts are connected with two DIN sockets (13) and
(14) at the unit rear.
The operation lines permit switching on and off the switching contacts by program control. You can
program the operation lines in “Fixed value entry mode” (chap. 6) as well as in the “Program editor”
(chap. 8.2) via the operation lines (switching state “0” = Off, switching state “1” = On).
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