- Motor Horsepower - 3/4 HP
- Motor RPM - 3600 RPM Variable
- Lances - 24" and 36" are
available. Note that 12" of lance length are contained within
the unit shroud
- Body Size - 8" Diameter x 17"
Long x 12" Base Flange - Suspension Hook 14" above body
- Customer Requirements -
Compressed air source (90-100 PSI), Overhead Hoist, Dry
Nitrogen, Argon, or proprietary dry gas
- Low Cost With High Efficiency
- Stainless Steel Construction
- Variable Speed Air Motor
- Portable and Lightweight - Under
- Versatile - Can be used in
dip-out or crucible furnaces with capacities from 40 lbs to 3000
- Unique one piece lance reduces
cost by eliminating shaft / impellor design
- Eliminates use of hazardous
degassing tablets and chlorine or Freon gasses.
Included with Purchased Unit
- Degas unit, combination air
regulator / filter / lubricator for air motor, four standard
lances (non-impellor). See system picture to the upper left.
- Customer supplies
interconnecting hoses for compressed air, filtered gas, and
inert gas to suit the needs of the installation.
Degas Times (Estimated)
- 70–500 pound crucible: 1–5 minutes
- 500–3000 pound crucible: 5–10 minutes
- Three leg mounting for support on flat
top crucible furnaces
- Impellor style lances available
- Reduced pressure tester for sample
comparison to national and metallurgical standards
The degassing of aluminum is based on the
principle that dissolved hydrogen gas will move from an area of high
concentration (in the melt) to an area of low concentration (in the inert
gas). Hydrogen gas disperses in molten metal as it would if it were released
in any confined space. It will maintain a constant concentration throughout
the melt. Hydrogen gas can migrate in liquid metal almost as fast as it can
in air. Therefore, it is unnecessary to bring every ounce of metal in
contact with the inert gas. The efficiency of aluminum degassing is
determined by two factors, the transfer rate across the metal/gas interface
and the total surface area available for transfer.
Traditional hydrogen degassing systems bubbled
specialty gases (Chlorine, Freon, or SF6)
through the metal to speed the hydrogen transfer across the metal gas
interface into large bubbles. There was a practical limit to hydrogen
removal on humid days because as the large bubbles would break the surface,
an increased surface area of metal was created which then absorbed more
hydrogen from the humid atmosphere.
Chlorine was the original gas of choice but due
to its hazardous nature, most foundries switched to other gases. However,
many foundries have not considered the hazardous materials released by the
breakdown of any specialty gas used.
Rotary degassing works on the principle of
increasing the surface area of an insert gas exposed to the metal. The
larger surface area increases the rate of transfer from metal to the inert
gas. The smaller the bubble size for a given volume of gas, the greater is
the surface area. For example, a 1” diameter bubble of gas has a surface
area of 6 square inches. If the same bubble is divided into 1/16” diameter
bubbles, the surface area is increased to 96 square inches. In other words,
if the same volume of gas is used and the diameter of the bubbles are
reduced to 1/16th the original diameter, the total surface area is increased
by a factor of 16. The smaller bubbles disturb the surface of the melt less
reducing additional hydrogen pickup from humid atmospheres.
This degassing unit is recommended for dry
nitrogen or argon. Compatibility with specialty gases cannot be guaranteed.
All parts of the unit exposed to gas except for the graphite lance are
either stainless steel or Buna-N (seals). A four minute degassing time for a
400 pound crucible is common when nitrogen gas is used. There is no
practical reason to use expensive specialty gases (costing up to $500 per
bottle) when a $20 bottle of nitrogen will do the same job. Also, no toxic
emissions are produced from nitrogen gas.
Whenever degassing is a requirement of the melting process, it is desirable
to verify the effectiveness of the degassing process. Palmer supplies a
simple, easy to use partial pressure test unit for this verification.
To use, the operator warms a sample cup, dips
the cup into the furnace for a metal sample, quickly places the sample into
the vacuum chamber, and starts the vacuum pump.
The aluminum solidifies under a vacuum causing
any entrained hydrogen gas bubbles to expand greatly. Once solid and cooled,
the sample is cut in half and compared to the chart below for gas level
Palmer Degasser - Animation.
Portable Rotary Degasser Lowers Aluminum
Degassing Cost (Foundry Management &
Gas Comparative Analysis.
Portable Rotary Degasser for Aluminum.
Typical Results of Nitrogen - Before and
RReduced Pressure Test Samples.
Complete Degasser Kit.