Bridge formation

Bridge formation is a phenomenon that cannot entirely be avoided in induction furnaces. If there is no proper heat-conducting contact between the liquid melt and the material above, the crucible is said to have a bridge. This phenomenon can occur for example due to material becoming jammed above the melt or a ceramic cover over the melt due to superheating and break-up of the ramming mix. To avoid this happening, the furnace should only be recharged with so much material so that a smooth surface can still be seen in the crucible. If a bridge has nevertheless formed, the furnace should be tilted, and the bridge broken up with extreme care. In MF furnaces, the bridge can sometimes be melted at low power. Serious damage and injury to personnel has in the past been caused by the uncontrolled melting and breaking up of the bridge in the basic position.