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System diagnostics of bell-type furnaces thermal separation

Main indicator of metallurgical production is quality of the products. Thus one of the most important elements of the technological process is heat treatment. All kinds of hot-rolled and cold-rolled steel have to be heat-treated: sheets, pieces, wires, rails, pipes, tapes, etc.

Main indicator of metallurgical production is quality of the products. Thus one of the most important elements of the technological process is heat treatment. All kinds of hot-rolled and cold-rolled steel have to be heat-treated: sheets, pieces, wires, rails, pipes, tapes, etc.

During cold rolling, stamping or drawing the grains of the metal deform and crush. This effect is called hardening. The hardening increases metal hardness and reduces its ductility, causes brittleness. Recrystallization annealing is used to eliminate hardening. In the shops of cold rolling, recrystallization annealing is used as:

  • procedure prior to the cold processing of metals by pressure – in this case, the material becomes more ductile, easier for its further processing;
  • output type of heat treatment – end product or semi-finished product get the required production specifications;
  • intermediate step in the metal cold deformation process: annealing makes possible to remove hardening effectively.

To implement this type of heat treatment in cold-rolling shop of JSC “Zaporizhstal” bell-type furnaces are used.

  • Client JSC "Zaporizhstal"
  • Skills Automation
  • Website https://www.zaporizhstal.com
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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:

  • gas consumption;
  • air consumption;
  • consumption of shielding gas;
  • consumption of combustion products.

The main disturbing effects in the metal heating process are:

  • change of shove’s characteristics (weight and size of the roll, metal brand its thickness, coiling density);
  • pressure change and caloric content of gas;
  • change of pressure in furnace.
  • Display panel
  • Cabinet of technology automation
  • Blocks of remote input/output

Control actions:

  • shove’s temperature;
  • temperature under the muffle;
  • pressure in the furnace;
  • pressure in the breeching.


  • analysis of the technical process and the timely prevention of emergency situations;
  • more efficient use of existing aggregates and equipment by reducing the downtime of production equipment and consumption of raw materials and energy resources;
  • improvement of reliability of aggregates and equipment;
  • improvement of quality and competitiveness of manufactured products.

Centralized supervisory control and diagnostics of electric equipment system is intended for:

  • automatic registration of monitored parameters, operator’s actions and events for the purpose of their subsequent analysis;
  • ensuring of reliable and safe exploitation of the bell furnaces’ equipment.


  • reception of discrete and analog (physical) signals from diagnosed electric equipment;
    • the total number of analog input channels – 192, из них:
      • 96 channels maximum amplitude of 500V (with the normalization);
      • 96 channels maximum amplitude of 100 mV;
    • the total number of discrete input channels – 96 (230V);
    • he total number of digital output channels – 96 (relay, 3-5A, 230V);
  • normalization and individual galvanic isolation of the received signals;
  • real-time scale of changes in the physical analog and digital signals in the manner of graphs;
  • mnemonic scheme displaying the progress of the technological process on the screen of the firmware complex for monitoring and archiving (CMA), and supervisory control device (USC);
  • maintenance of the alarms report in text form – the protocol of change of the of state diagnosed equipment and output of defined signals beyond the permissible limits;
  • continuous recording of terms of the received signals into an information file (buffer type endless tape) with a specified interval;
  • possibility of convenient revision, analyzing and printing data from the archive;
  • the minimum recording interval – 20 ms;
  • archive depth – not less than 24 h;
  • processing the received signals and information, analysis and fault detection and deviations of the technological process in accordance with a predetermined algorithm of equipment operation;
  • alarm system in case of emergency in the diagnosed equipment;
  • the accumulation of statistical data on the process and reporting for certain periods of time (shift, day, month, etc.);
  • Ethernet connection between the nodes;
  • the possibility of organizing connection with MIS or a higher-level control and diagnostics system via Ethernet or RS-485/422;
  • backup power to all components of the system in case of voltage disruptions;
  • ease of system maintenance;
  • the possibility of further change, extension of functionality and scalability of the system, including the forces of craft services.

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