Simple Solutions That Work! Issue 9

BACK-2-BASICS Contact: PAUL COOPER [email protected] potential for dross creation and thus metal loss. There are two major causes of dross creation when transferring metal from the furnace: aluminum exposure to oxygen and turbulence in metal flow. While gravity is free, the use of tap out plugs and a trough with a downward slope makes it very challenging to control the flow of metal. If the flow is too slow, you freeze the metal, too fast and you create turbulence which has the effect of exposing more aluminum to the air than necessary or desired, increasing dross creation and reducing the amount of metal available for sale. In a traditional transfer pump, there is a greater ability to control the flow of the metal by using the variable speed drive that controls the pump motor. Depending on how high the metal needs to be lifted to get it out of the furnace and to its next point of use, the speed of the pump, and thus velocity of the metal can be controlled. The use of piping, however, restricts the flow of the metal and can result in turbulence as the metal exits the piping, given that the metal is forced out of the piping at a higher velocity due to the need to satisfy the lift requirements. The launder transfer pump best addresses the velocity issue by utilizing a “chimney” in which the metal rises up without the restriction of a pipe and with the significant benefit of limiting the amount of air the aluminum comes in contact with, thus creating a skin 25 that protects all the metal beneath it from oxidizing. As the metal exits the chimney and enters the launder it flows quiescently to the next point of use, with no added dross creation. It has been our experience that this method of metal transfer can reduce dross creation by more than 50%. Safety & Accident Prevention A very important factor in today’s manufacturing environment is safety and accident prevention. Systems that utilize mechanical pumps and remove the operator from any potential direct contact with molten aluminum are much safer to operate and significantly reduce the possibility of dangerous accidents. Another area for exploration in a future article related to these metal transfer systems is metal quality, as here also there are many benefits to explore. There are many plant specific factors that will influence the decision as to which metal transfer methodology to deploy. Focusing on reducing metal lost to dross creation should be very near the top of the list for all molten aluminum processors. To the extent you can reduce aluminum contact with oxygen and turbulent metal flow, you will have more saleable metal at the end of your process.