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SIROLL cis BOPS Breakout Prediction System For a Higher Casting Productivity

initial source:http://www.industry.siemens.com/broschueren/pdf/metals/2004-04-14_140545_BOPS_e.pdf

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Enhancing continuous casting plant output

The most sensitive part of the continuous casting plant is the mold area. It is here that the liquid steel must form a solid shell before it is drawn into the casting machine. During the growth of the shell, problems such as sticker and air gap can occur, which lead to a breakout when the defective zone leaves the mold. The result is production downtime and expensive repairs. Siemens’ Breakout Prediction System SIROLL cis BOPS helps avoid these problems by indicating a sticker or air gap in a timely manner, enabling reduction of the casting speed and correction of the defective zone. SIROLL cis BOPS is so effective, in fact, that virtually 100% ROI is achieved with the avoidance of a single breakout.

A number of potential problems

The greatest problem in the mold is a sticker, which is caused by locally high friction between the strand shell and the mold (Fig. 1). The strand shell sticks to the mold copper plate, and, by drawing out the strand, the shell is stressed and breaks, so that liquid steel splashes onto the copper plate. Another problem involves air gaps (cracks) between the strand shell and the mold plate, which are often formed at the edge between narrow and broad faces (Fig. 2). Due to the low thermal conductivity of the air, the shell cannot be cooled adequately, and it remains too thin. Figure 3 shows the temperature patterns inherent to both problems.

Figure 1 Friction between the strand shell and the mold
Figure 1 Friction between the strand shell and the mold

Figure 2 Air gaps (cracks) between the strand shell and the mold plate
Figure 2 Air gaps (cracks) between the strand shell and the mold plate

Figure 3 The temperature patterns inherent to both problems
Figure 3 The temperature patterns inherent to both problems

Predicting breakouts while avoiding false alarms

Evaluation of the temperature patterns and prediction of breakouts are performed by the advanced SIMATIC® S7-400 PLC running the SIMATIC WinCC open visualization system. Thermoelements measure the temperatures in the upper mold area and transfer them to the SIROLL cis BOPS, which detects temperature patterns for both sticker and air gaps. Whereas conventional systems use static trend monitoring, SIROLL cis BOPS relies on fuzzy logic for dynamic trend recognition. The values for temperature and change of temperature of each sensor serve as inputs for evaluation by fuzzy logic of the probability of a breakout. The feedback of the last calculated probability contains the compressed history of the measured trace (Fig. 4).

Figure 4 Compressed history of the measured trace
Figure 4 Compressed history of the measured trace

A simple yet smart algorithm gives the system a very fast reaction time. This makes SIROLL cis BOPS especially useful in the high-speed, thin-slab caster. Since SIROLL cis BOPS must detect break-outs reliably, while avoiding expensive false alarms. restrictions are placed on the system that include:

  • Close monitoring of the casting speed
  • Automatic deselection of defect thermoelements
  • Automatic deselection of thermoelements in case of width change.

Benefits that really satisfy you

For some time now, the new breakout prediction system has been in operation at several major steel mills, including Huttenwerke Krupp Mannesmann (HKM), Germany; Essar Steel, India; Saldanha Steel (thin slab caster), South Africa; and Krupp Thyssen Nirosta (KTN) in Germany. In all cases, customer satisfaction is based on a number of solid benefits:

  • Safe detection of stickers and cracks
  • Avoidance of false alarms