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OPERATION
THEORY OF OPERATION
Vacuum
Vacuum is supplied by an external vacuum supply (a pump or building system) connected to the
vacuum port on the back of the oven. Vacuum levels obtained in the oven chamber are dependent
on pump type and performance, valve settings, and the nature of the application or process,
including the volume of materials outgassed.
The chamber atmospheric pressure is displayed on the Vacuum Gauge on the main control panel.
The chamber should be sealed and evacuated at the start of a vacuum baking application. The oven
is not built to operate with the chamber exposed to atmosphere. Running the oven with the door or
the vent open risks destroying the vacuum pump, damaging the integrity of the oven chamber, and
may oxidize chamber surfaces.
Vacuum pumps and door gaskets should be selected on the basis of application type or process.
Pumps vary in suitability and safety depending on the outgassed byproduct types and moisture level
produced in the oven chamber. Gasket types are both resistant to and vulnerable to different
chemicals.
Gas Backfill
A gas supply can be connected to the vent port (backfill inlet) located on the back of the oven.
Nitrogen or another inert gas are typically used to avoid particulate contamination or the oxidation of
product that has not cooled down. The maximum allowed backfill pressure is 15 psi of delivery at the
port inlet. The port valve is opened and closed using the Vent control on the front panel.
Heating Options
The oven can either heat to and run at a constant temperature setpoint or execute a programmable
multistep heating profile with ramp up, heat soak, and ramp down intervals.
Heating in a Vacuum
In conventional ovens, powered elements transfer heat into the chamber air. The heated air then
circulates by natural convection or blower fan action, and surrounds the product on the shelves,
gradually bringing it to temperature. In a vacuum oven, heat transport takes place primarily by
conduction. The oven heating elements are located inside the chamber walls or floor, which in turn
transfer heat to the shelves. Each shelf then transports heat to the products or samples resting on it.
Direct radiant heating through infrared emission in a vacuum environment provides poor
temperature uniformity compared to conductive heating.
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