Simple Solutions That Work! Issue 12

17 BACK TO BASICS O ne of the most frequent questions we get asked is: what is the right furnace for my operation? Our next step is to ask questions to get to the heart of what it is you are trying to do. Yes, we know you are trying to make an aluminum casting either by die casting, permanent mold, sand castings, tilt pour, investment casting and of course lost foam. But other than making lots of parts, what are your goals for this casting? Be prepared to discuss: 1. Goals, in priority: highest quality metal, low upfront costs, energy cost, metal melt loss, and safety. 2. Alloys you are using. 3. Temperature desired to cast your parts and if you are modifying the alloy in any way. 4.Do you want to melt chips or recover inserts? 5. Space you have to work with. 6. Do you need gas, propane, oil or electric fired furnaces? 7. Preference for central melting or machine side melter holders. Once we have this information and your plant layout, we can better recommend what type of furnace best fits your plant and goals. Let’s cut through all the hype that is out there and define the basics of each type of furnace. I will not get into induction melting of aluminum simply because we do not build those furnaces. FUEL FIRED DRY HEARTH FURNACES This type of furnace is well suited to knock down and melt heavy solids as cold solids absorb heat readily. Solids are loaded onto a dry tapered ramp and many manufactures directly fire at solids like sows or ingot bundles loaded on the sloped ramp. The metal loss from direct impingement of the flame and burner velocities is quite high especially on lighter weight scrap. The efficiency of these type of furnaces ranges from 1800 to 2000 Btu per pound. Because you have two separate chambers (melt and hold) and two separate combustion systems these tend to cost more than a low headroom reverb melter. DAVE WHITE Sales Support THE SCHAEFER GROUP ARTICLE TAKEAWAYS: • Understanding each type of furnace • Furnace energy usage • Metal melt loss for each furnace BACK TO BASICS: WHEN CHOOSING AN ALUMINUM MELTING FURNACE Gas fired Dry Hearth Melter FUEL FIRED STACK MELTERS This type of furnace is typically used for ingot and scrap melting only. This design is an off shoot of dry hearth as the ingots are loaded into a tall tower (stack) type flue where the stack is supposed to be kept full. At the bottom of the stack is a sloped dry ramp and usually opposing burners firing directly at the stacked-up ingot and scrap. The spent gasses comingle with the balance of the ingot and scrap stacked up in the tower. This allows the flue gases to transfer their heat into the load prior to exiting the furnace at a lower temperature Continued on next page