Operator’s Manual for Prentex Model 9900E Vacuum Degassing Oven
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1. Introduction and setup: Model 9900 Vacuum Degassing Oven
1.1 After removing the unit from its shipping carton, remove everything from the vacuum
chamber.
1.2 Connect the power cord to the receptacle in the back of unit and plug it in to a standard
110-125 v ac. 60HZ outlet [10 Amp or greater capacity].
[For export systems: 230-240 v ac., 50 Hz, 5 Amp capacity.]
1.3 Turn the power switch “On”. The control display should light up, with the word “idLE”
displayed, alternating with the current air temperature.
2. Install Main O-Ring Gasket
Place an orange O-Ring gasket (supplied with the PAV) in the groove on the flange and
then place the cover on the vacuum Oven.
A. The O-ring will tend to be too small until it heats slightly and expands to the groove’s size -- If it is too
small, stretch the O-Ring between two hands to get it to fit into the groove.
B. An alternative method to set the O-ring is to place the edge of the lid on the O-Ring and roll it into the groove as you
close the vessel.
Be aware that after several uses, the O-Ring, once seated correctly will tend to stay in the groove between uses and
will require little attention other than periodic cleaning.
Note: When the Vacuum Oven is heated, the O-Ring may expand and bulge out of the groove when the lid is removed.
Since it is important to have a properly fit O-ring, one solution is to cool the O-ring in water and place it back in the
grove (if it does not need cleaning or has not been pinched).
An alternate solution is to keep a spare O-Ring handy to replace in the grove.
2.1 Replacement O-Ring Information. An O-ring should be replaced when it will no longer shrink to normal size or has
been pinched in a manner to prevent it from expanding as necessary to seal the lid properly. The O-Ring gasket is
Parker size 2-274; desired material is Silicone Rubber. Viton may be used, but has less resiliency and it may be more
difficult to get a good vacuum seal.
2.2 Window O-Ring Gasket. The viewing window in the lid is also sealed by an O-Ring gasket. This gasket will probably
not require replacement unless you break the glass. A new O-Ring is furnished with replacement glass, but if required,
it is size 2-161, and the desired material is Silicone Rubber.
3. Absolute Vacuum and Adjusting Your Prentex Model 9900 Vacuum Degassing Oven’s Vacuum Pressure
Adjusting vacuum pressure requires awareness of the following:
3.1 The AASHTO PP-1 and ASTM D-6521 Standard Practice for Accelerated Aging of Asphalt Binder Using a
Pressurized Aging Vessel [PAV] specify degassing the PAV-aged samples at 15±2½ kPa absolute pressure [25.5 ±
0.74 in / Hg negative gauge pressure at standard atmospheric conditions].
3.2 Relative Pressure Vacuum Gauges. Vacuum gauges commonly used in the U.S. measure vacuum relative to the
local atmospheric pressure and express it as a negative number. Vacuum is indicated as a negative gauge pressure
below the ambient atmospheric pressure, measured by the amount of mercury supported in a manometer in inches [in
Hg] or millimeters [mm Hg], or the force exerted by the mercury column, expressed in kilopascals [kPa]
3.3 Thus, the vacuum level of ambient atmospheric pressure is “0" in negative gauge, whether in Hg, mm Hg or kPa. The
