Safe Use of Degasser Equipment

The portable rotary degasser uses a one-piece low profile expendable graphite lance/impeller available in 24" & 36" lengths. The lance/impeller portion of the degasser is submerged in the melt. A purge gas (dry nitrogen or argon) travels down through the rotating lance/impeller where it is sheared off into small bubbles. Lance rotation is provided by a 3/4 h.p. variable speed air motor. The speed of the motor is controlled by a combination regulator/filter/lubricator. The following steps are recommended for the safe use of the degasser.

Make sure the operators are properly clothed for handling molten metal. Minimum requirements are safety glasses, face shield, and high temperature apron leggings and spats.

Preheat the lance to remove any moisture that could cause an explosion in the melt.

Turn the inert gas on and set at a low flow level. This precaution is to prevent molten aluminum from entering the cold lance and solidifying. If this occurs simply wait until the lance has heated up to melt temperature and the aluminum in the lance melts.

Lower the degasser into the melt until the lance is completely submersed. At this point the inert gas should be bubbling to the surface in large bubbles.

Turn on the air supply to the unit and begin degassing. In general the faster you run the unit the better. The higher the lance speed the smaller the gas bubbles. There is often a period of lance instability (wobble) while the unit is coming up to speed. When the lance is at full speed it should run without any wobble. CAUTION: DO NOT START LANCE ROTATION UNTIL LANCE IS SUBMERGED. SERIOUS INJURY MAY RESULT.

Increase the inert gas flow as high as possible without producing large bubbles. You can usually see small pinhead sized bubbles breaking under the oxide film on the surface of the melt. If you see large bubbles of gas breaking the surface of the metal while the lance is turning your inert gas flow is too high and should be turned down.

Run the unit for the time required for your process. The time required to fully degas your metal is dependent on your operating procedures. The best method to determine the time required is to test the melt is with a reduced atmospheric tester. If you require near complete gas removal make sure your tester is capable of producing a vacuum of at least 29" hg. Start testing at 4-5 minutes and increase or decrease the degassing time depending on the results. Remember that humidity in the atmosphere is a major source of hydrogen pickup. If you determine your degassing times on a dry winter day they may be insufficient on a humid summer day.

When the degassing is complete turn the inert gas to a minimum flow level, shut down the air supply to the motor and remove the unit from the melt. Do not remove the lance from the metal while it is still turning. The rotating lance will throw off small bits of molten aluminum that can cause burns. Be careful handling the unit as the lance will still be very hot and capable of causing severe burns and starting fires if placed near combustibles.