The thermal balance of the furnace, that is, the required reheating power of the furnace, is important for the profitability of any reheating, maintenance, or automatic casting furnace. Thus, with the current prices of electricity, for heat losses of 10 KW, higher costs are already produced each year, amounting to approx. From 15,000 DM.
If we also take into account that in medium and large channel furnaces, with a capacity of 30 to 100 tons, lining durations of 3 to 5 years and sometimes more are frequently achieved, the highest costs arising in this way amount to 45,000 – 75,000 DM. . throughout the entire service period. Therefore it is worth controlling the heat loss calculation with special attention. In any case, caution is advised. Too much insulation reduces the temperature gradient across the oven wall. The result is low outer wall temperatures and low losses at the beginning, but also unacceptably high intermediate layer temperatures, and with continued operation greater infiltrations into the coating. At the very least, the temperatures of the outer walls inevitably rise, and with it, of course, also the losses. It is also not uncommon for such a thermo assembly to end in breakage and significant damage to the coating and the installation.
In a suitable solution between tolerable heat losses and a safe dimensioning of the wall, the temperature of the intermediate layer between the working coating and the subsequent coating should no longer be in the liquid zone of the iron.
The line of the liquid state must be clearly found on the working coating, but by no means on the subsequent coating; However, the temperature of the intermediate layer is also 1120ºC and the radiant temperature outside is 180ºC.
For the choice of the type of assembly, in addition to the technology of the product, the total time invested for assembly until the moment of readiness for production is of course also particularly important for the expected life. Not so much for new installations, but for coatings that become necessary again, generally only 2 to 3 weeks are available, in isolated cases 4 weeks during company holidays.
The range of refractory products possible for reheating, maintenance, and automatic casting furnaces is undoubtedly very wide.