Vesuvius Crucible Company

Donald H Kings

John D Usher

Robin A Sommers

Both an apparatus and method for detecting slag in a flow of molten metal conducted through a ladle shroud are provided. In the apparatus, first and second conductive pins are mounted beside one another in a wall of the ladle shroud, the first being in contact with the flow of molten metal, but electrically insulated from both the wall and from the second conductive pin, the second being in electrical contact both with the wall and with the flow of molten metal. A voltmeter is connected between the two conductive pins for detecting differences in the electrical potential between them as molten metal flows through the shroud. Abrupt changes in potential caused by the passage of a metal slag interface through the shroud indicate the presence of slag in the molten metal.

Slag detecting apparatus and method

A probe system for reliably monitoring a condition in a metallurgical process is provided which includes a probe having a circuit for generating a low DC voltage signal indicative of a condition in the metallurgical process, and an impedance monitoring circuit electrically connected to the probe circuit for passively and continuously measuring the impedance of the probe circuit to determine its reliability without disturbing its DC signal. The probe may be a slag detector, a thermocouple, a sulfur sensor, or an oxygen sensor of the type used in steel manufacturing processes. The impedance monitoring circuit includes an oscillator assembly and a known impedance that is serially connected to the probe circuit by means of coupling capacitors that prevent the conduction of potentially biasing DC currents through the probe circuit. A band pass filter circuit having an input is connected between the known impedance and the probe circuit for generating a residual voltage which, when compared to the voltage applied by the oscillator circuit, indicates the impedance of the probe circuit. The impedance monitoring circuit advantageously detects a failure condition in such probes even when the failed probe continues to generate a low DC voltage that spuriously indicates a normal operating condition.

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Bicester, United Kingdom

Donald H Kings