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Induction Furnace Warnings

Induction furnaces are an electric-powered means of melting metal. As with any industrial equipment, there are safety risks associated with operating an induction powered furnace. There are three specific hazards commonly attributed to working with induction furnaces. These are wet charged materials, sealed scrap and bridging.

  1. Wet Charged Material

    • A wet charge is any piece of scrap metal that contains moisture. Water or moisture present in scrap metal will instantly be converted to steam upon contact with molten metal. Moisture molecules may expand up to 1,600 times in a single instant. The violence of this reaction causes an explosion capable of launching large amounts of molten metal into the air. Damage to the furnace can occur, increasing the likelihood of a leak or secondary explosion. Induction furnaces are cooled by coils of water that wrap around the crucible in which the metal is melted. This increases the risk associated with adding wet metal to the furnace, as an explosion may rupture those cooling lines and cause the coolant to leak into the furnace. The coolant hitting the molten metal will create additional explosions.

    Sealed Containers

    • Many foundries melt scrap metal. This process often involves melting metal products back down for repurposing of the raw metal. Air and gases expand as they are heated. Adding a sealed-off, closed container into a furnace will cause the air or gas inside the container to expand very rapidly. Should the pressure inside the sealed container breach the container walls, an explosion will occur. Such an explosion may cause molten metal to be thrown from the furnace, landing on operators or sensitive equipment.

    Bridging

    • When metal being added to a furnace fails to make contact with the molten metal already inside the furnace, it is called bridging. Metal being added, called the "charge," is significantly cooler than the metal that is already melted. Adding cooler metal helps regulate the temperature of the molten material inside the furnace.

      Bridging occurs when a crust of slag forms across the top of the molten metal. This layer contains impurities and air or vapors. If the charge fails to penetrate this layer, the slag will insulate the molten metal and cause it to overheat. The charge will remain separate from the molten metal and the molten material will sit in the crucible and bake. Eventually the molten metal trapped in the bottom of the crucible will become hot enough to eat through the crucible and furnace lining and cause a fire underneath the furnace.The fire may destroy the hydraulic controls of the furnace, electrical controls and colling lines. If the molten metal contacts the coolant, an explosion will occur.

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