A sealing apparatus for a slag door of a metallurgical furnace, having a mounting assembly for mounting the apparatus to the furnace, and at least one closure element, moveable from an open position that is exterior of the slag door opening, to a closed position that effectively seals against the slag door and extends into the slag door opening with the rear panel of the closure element(s) being proximally aligned with the interior wall of the furnace. The apparatus may also have at least one wiping component moveable so as to sweep across the lower surface of the slag door to remove obstructions.