Stripping is rarely carried out nowadays in view of the relatively low costs of acidic tamp- ing compounds. In stripping, the crucible wall, which is infiltrated with iron, is removed with the aid of compressed air hammers. The thickness of this layer ranges from 30 to 50 mm. After the removal of the waste, the “crucible wall” is cleaned of loose particles. A lost tamping form is now put in place and the dry compound filled in. After vibration and compacting, the crucible furnace is start- ed up again as for a normal relining. This process saves the costs of the insulation behind the wear lining and the proportion of the compound remaining in the furnace of approx. 30%.
If the crucible is pressed out with the aid of a crucible removal device, the costs of stripping are only worthwhile in rare cases. For mains frequency furnaces over approx. 12 t, more economical repair can often be effected by means of partial stripping of the lower section. Stripping is carried out over about the lower third of the crucible height, and an approx. 60 mm smaller repair template then positioned. A nominal diameter of 1,190 mm thus gives approx. 1,130 mm. This is pre-heated with a gas burner and then liquid-sintered.