Furnace covers serve essentially to avoid heat losses, and as safety devices for the operating personnel, to screen them against the heat radiation and prevent the danger of falling. Furnace covers are made of steel plate with a ceramic cladding, which is as a rule cast. An imaginary furnace cover is set in place under processor operation of a crucible furnace at the end of the melting process, and all stored values of the melt are processed, and displayed on the screen or printed out for the information of the operator (ready for further measures).
Larger furnaces with cover diameters of over approx. 1,200 mm have an additional small cover that can be swung open by hand. Through this opening, additives can be added to the melt or the temperature measured.