Insulation
Thorough removal of damaged or worn coil insulation is important to ensure that the new layers of insulation are installed smoothly and have good physical and dielectric properties. Depending on the extent of damage to the coil, it is decided whether the insulation will be removed in its entirety across the entire profile or whether the original insulation will withstand the harsh conditions of furnace operation and only be supplemented with new layers in the next phase.
Repairing local damage
When repairing local damage, the original disturbed insulation is carefully dismantled. The surface of the copper profile is degreased and then finely sandblasted to bare copper. Local repair is usually chosen when the insulation is burnt by liquid metal that has penetrated the lining. As a rule, the penetration of liquid metal up to the coil caused by the collapse of the lining will cause insulation burns of local significance.
Removing the damaged original insulation
Removal of the insulation in the full coil profile is accomplished in a resistance furnace by burning off the complete insulation. An indicator of such an operation is, for example, mechanical damage to the coil caused by insufficient tightening of the side and bolt bolts tightening the coil in the furnace, or chemical damage caused by an aggressive alloy permeating the lining and the refractory grouting. It should be remembered that frequent thermal stresses on the coil in the resistance furnace, together with mechanical loading, can cause a shortened coil life. After removing the damaged original insulation, the next step of the repair is to chemically clean the deposits inside and outside the coil profile.
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