Simple Solutions That Work! Issue 5

Electric immersion elements used in aluminum furnaces are normally in either vertical or horizontal posi- tions in the molten metal bath. These heating methods allow the holding furnace to be: • More compact – since the heat necessary to hold the metal at temperature is introduced directly into the molten metal without having to deal with a radiant heat enclosure “thermal head chamber” mounted over the metal and external to the dip well. • Lower maintenance – due to the entire furnace acting like an exterior dipwell; the advantageof this is a result of havingno thermal head chamber and the refractory wear and tear that occurs at the molten metal contact line. The need for furnace cleaning is greatly reduced as well, to once every 3-4 days! • Extremely efficient – the electric elements are housed in top- quality sialon high heat transfer protection tubes (4-to-6 year’s life). It is typical to hold the molten aluminum at production temperature for 18-to-19 BTU/ lb of metal held in the furnace. (0.0052-to-0.0053 kWh/lb). The low heat loss thermally stingy linings used in SGI furnaces combine with the immersion element advantages in providing themost energy efficient holding furnaces in the industry. • The simplest and cleanest main bath top available – the way to achieve this objective is to horizontally mount the immersion tubes and the electric element terminal connections low in the furnace wall (near the floor of the furnace). There are no impediments of terminal boxes and electrical connections on the top of the furnace, which is the case when vertical immersion tubes are used. This leaves a clean, unencumbered and business-like top to the main bath. Here again, this leads to a more compact and efficient furnace that holds simply the amount of molten metal you want. The rule of hold capacity is 3 times what you cast through the machine per hour. This provides the greatest flexibility in delivering metal to the holder. It means you can deliver metal to this holder only once every half hour. As opposed to radiant furnaces that have to have the metal close to the heat source or they will lose temperature. • Themost comfortable furnace to work around – it is electric and makesnonoise,nordoes ithaveto flue and products of combustion as in a gas-fired holding furnace. The cooler exterior of this more compact furnace leads to less worker fatigue and thus more productivity. • The most accurate in close tolerance temperature control – when the furnace is designed to provide the most compact package (less wall and floor area for heat losses) the in-the-bath immersion elements allow for the closest process temperature control achievable. SGI further enhances this advantage by using full proportioning SCR power controls to meter in only the exact amount of energy required at any given moment. 7