Typical construction of a bath channel furnace

In order to allow operation, a minimum amoimt of molten metal needs to stay inside the crucible and channel. The crucible needs to stay filled up to one third of its capacity. Two values are usually quoted when the capacity of a holding fomace is defined, these are total capacity and useful capacity for example 60/35 toimes. The difference between these two values represents the amount of metal that must be retained in the furnace. 

Thermal losses through the cooling water and the furnace wall are low compared to those in the coreless induction furnace. Equipping the furnace with pouring channels according to the teapot principle allows for a reduced oxidation of the melt and wearing of the refractory. 

Due to the large content of the crucible, any changes in the melt composition are flattened out. This principle however counteracts the flexibility of the furnace, as changing to another melt composition requires a long transition period. In practice, the melt composition is therefore kept fairly constant. 

Output requirements are an important consideration when deciding the size of a channel furnace. The choice of a smaller furnace may be advantageous. Although a smaller furnace is less efficient, the loss in efficiency will be offset by its reduced annual power consumption 

Additionally the refractory lining (acid Si02 based, neutral AI2O3 based, or basic MgO based) may add a small amount of dust particles to the emission. 

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Figure 2.15 Typical construction of a bath channel furnace [55, ETSU, 1993]...

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