Bell-type furnace – is a batch furnace for heat treatment of sheet rolls, strips and wire coils. The main feature of the furnace – is presence of two bells: internal, which protects the metal from oxidation (muffle); and external – is lined with refractory bricks, on which are mounted the burners or electric heaters. Heating of the products is carried out in a protective gas atmosphere.
Bell-type furnace operating principle is determined by the technology process, which is divided into three approximately equal steps of: heating up to 650-800°С, cooling under the muffle to 150°With and without it and the last stage – unloading and loading. The equality of time in stages allows you to use three stands with one of the heating hood and two muffles. Download metal ends on lowering stand on top of the foot rolls muffle and heating bell. Then flushed with protective gas (usually a mixture of 95% N2 and 5% Н2) and using circulating fan is its circulation. Then turn on the burner. The products of combustion pass between the heating hood and the muffle, and with the help of the injector (injects Wednesday – the air compressor) are removed in the stacks and in smoke hog. The temperature of the smoke in front of the injector about 630-660 °С. n bell-type furnaces, the physical warmth of the smoke is usually not recycled, what can be considered one of the drawbacks of the furnaces.
The heating time in the bell-type furnace is the main factor affecting fuel consumption. The time depends on the heat transfer conditions at the sidewall of the metal rolls.
Bell-type furnace from the viewpoint of automatic control is capacitive static object and it is characterized by following input parameters:
Centralized supervisory control and diagnostics of electric equipment system is intended for: