One of the key components of the complex of equipment required for the operation of vacuum-degassing units is the system that measures the level of the melt in the ladle during vacuum degassing. This system was developed by the authors of this article. Prompt determinations of this parameter are necessary because the plant lacks enough overhead electric traveling cranes to quickly transfer more ladles to the degassing section for large heats. Thus, only a small part of each ladle used in vacuum degassing is left unfilled. Here, the freeboard AH --the distance from the still surface of the melt to the top edge of the ladle --is usually within the range 500-600 mm. The measurement system operates on the principle of radar. It entails the continuous emission of a frequency-modulated radio signal, reception of its reflection from an object, and calculation of the mean frequency of the difference signal --which is proportional to the distance to the object.The German company "MESSO, ~ as the main supplier of the equipment of the system, devised a method to link all of the elements of the system to the object (the vacuum degassing unit) by means of the initial data.The radar part of the system consists of an SHF block which continuously emits a frequency-modulated signal with a carrier frequency of 37 GHz (wavelength 8 mm) and a block that analyzes the signals reflected from the surface of the melt. The analysis block f'tlters out noise and analyzes the information, changing it into an analog signal for subsequent representation on the display of the control computer and recording by the recording equipment. A protective aiming device was developed to allow the SHF block to function properly in an environment of high gas and dust concentrations and thermal noise and permit adjustment of the emitter, i.e., checking of the direction of the radio waves in relation to the surface being monitored. The device includes a water-cooled thermostat that houses the SHF block and a scavenging chamber. A protective plate that is transparent to radio waves is positioned in front of the emitter to protect the antenna, part of the system. The protective aiming device, with the SHF block enclosed, is mounted directly on the cover of the vacuum-degassing unit, while the signal analysis block is located in the control room.The level-measurement system was calibrated on a still steel surface before it was placed in operation. The aiming" device was used to adjust the vertical position of the SHF block for the maximum intensity of reflected signal. The calibration was done for five distances to the object (target) within the range 2-4 m. For each distance, we recorded the current of the output signal and the distance from the surface of the receiving-transmitting antenna of the SHF block to the surface of the bath. Two measurements were obtained for each level: distance to the target was decreased for each level in the first series of measurements and increased in the second series. The dependence of the output current on distance is distin...
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