Sliding closure for metallurgical vessels

The invention concerns a sliding closure for metallurgical vessels according to the preamble of claim 1.

A sliding closure of this type is disclosed in WO 03/080274. Closing parts for sliding closures of this type are obviously exposed to heavy wear and therefore have to be replaced frequently. For economic reasons, however, every effort is made to use these closing plates for as long as possible. In order nevertheless to guarantee a high level of operational safety and detect any nascent operational faults at an early stage, it is known from WO 03/080274 to equip the sliding closure with at least one measuring apparatus with which the position of the closing plates, which are displaceable with respect to each other on sliding areas, can be measured and evaluated in terms of their change transverse to the sliding areas. By measuring the distance between the housing parts which accommodate the respective closing plate, any changes in the position of the closing plates, such as e.g. those which arise when steel melt penetrates between the closing plates and there forms a thin sheet, are diagnosed at an early stage. This can prevent steel melt from flowing out uncontrolled between the closing plates.

The problem with measuring the position of the closing plates lies in the large temperature range in which the distance and/or change in distance has to be measured. The temperature differential between the start temperature (e.g. 24° C.) and the end temperature (e.g. 345° C.) is considerable (here it is 321° C.). This means that the distance in cold and in hot condition may vary by several millimetres.

The present invention is based on the problem of creating a sliding closure of the type mentioned above which has a high level of operational safety, and in which, at little expense, unacceptable deviations in the position of the closing plates can be determined with sufficient accuracy while taking account of distance changes due to temperature.

This problem is solved according to the invention by a sliding closure with the features of claim 1.

Further preferred embodiments of the sliding closures according to the invention form the subject matter of the dependent claims.

The sliding closure according to the invention is fitted with a measuring apparatus which comprises two exploring coils attached side by side on a coil body built into the two housing parts, and a core placed in a central opening of the coil body, longitudinally displaceable in the axial direction of the coil body, which together form a differential throttle. When the distance between the two housing parts changes transverse to the sliding areas of the closing plates, the core is displaced from a central position with respect to the exploring coils whereby a voltage can be generated which can be transmitted to an evaluation unit. A good reproducibility of the measurements of distance changes at various temperatures was achieved with the measurement device. Temperature drift is small due to the compensation of the two exploring coils with respect to their change in resistance, which enables a formula-based temperature compensation to be realised. This allows distance changes in a measurement range of 8 mm to be determined to an accuracy of less than 0.1 mm. The sliding closure according to the invention thus has a high level of operational safety. Faults and in particular breakouts, in which often the entire sliding closure mechanism and possibly also parts of the continuous casting plant can be destroyed, can be largely prevented. Assembly faults on the sliding closure can also be detected and resultant breakouts can also be prevented.

FIG. 1 shows part of a sliding closure, comprising as closing parts at least two refractory closing parts that can be braced against each other in a way known per se, each disposed in a housing part and displaceable on sliding areas with respect to each other. For example this may be a sliding closure corresponding to that in WO 03/080274, FIG. 2, and which has a fixed, upper housing part attached to a vessel with the one closing plate and a lower housing part movable with respect thereto and provided with the other closing plate, where the movable housing part and with it the other closing plate is displaceable by means of a drive body into a closed or open position, as the case may be. The closing plates themselves are not shown in FIG. 1, and only the one housing part 1 of the housing parts is shown, the embodiment shown being the fixed upper housing part.

A guidance unit 2 is built into the fixed housing part 1—similarly to the sliding closure according to WO 03/080274, FIG. 2—which has a guide pin 4 accommodated in a housing 3, on the lower end 4a of which at least one guide element, e.g. a guide roller, preferably two parallel guide rollers, not however shown in FIG. 1, is or are attached. A spring element 5 is arranged at the perimeter of the guide pin 4, which is supported on one side on a lower shoulder area 3a of the housing 3 and on the other side on the guide pin 4 and presses the guide pin 4 upwards and with it the guide roller from below onto a guideway of the movable housing part. There is also a bearing ring 17 held in the upper part of the housing 3, which serves as a stop for the coil body 11 and for the guide pin 4.

There are of course several such guide units 2 with spring elements 5 built into the fixed housing part 1, via which the lower housing part is pushed upwards and the closing plates are tensioned against each other.

In accordance with FIG. 1, a measuring apparatus 10 for measuring the position of the closing plates with respect to its change transverse to the sliding areas is assigned to one of these guide units 2. The basic parts of this measuring apparatus 10 are also shown in FIG. 2, and FIG. 3 shows a corresponding circuit diagram. The measuring apparatus 10 comprises two exploring coils 12, 13 attached to a coil body 11 (FIG. 2) and a magnetic core 15 located in a central opening 11a of the coil body 11, longitudinally movable via a non-magnetic connecting rod 16 in the axial direction of the coil body, which jointly form a differential throttle. The voltage changes caused by the movements of the magnetic core 15 from a central position as shown in FIG. 2 (in the middle, between the two exploring coils 12, 13) can be measured in a bridge circuit. The differential throttle can be operated with an ordinary commercial carrier frequency amplifier 19 with integrated phase demodulator 19 (FIG. 3).

According to the invention, the core 15 is assigned to the guide unit 2 or its spring-loaded guide pin 4 respectively, and is in fact built into the guide pin 4, with the tension rod 16 on its front face, at its upper end. The coil body 11 with the exploring coils 12, 13 (FIG. 2) is built into the fixed housing part 1 above the guide unit 2, in such a way that the tension rod 16 with the core 15 protrudes into the central opening IIa.

Changes in the distance of the two sliding closure-housing parts and the two closing plates respectively transverse to their sliding surface can be measured using the measuring apparatus 10. If, for example, steel melt penetrates between the closing plates, a thin sheet may form there which forces the closing plates apart. As the result of this, the lower housing part is forced downwards, against the force of the spring elements 5, and also the guide pin 4 supporting the guide rollers is forced downwards via its guideways. Also, the guide pin 4 fitted with the tension rod 16 and the core 15 is moved downwards in the housing 2 against the force of the spring element 5 and the core 15 is shifted out of its central position, at which the measuring voltage is zero, thus creating a voltage which is transmitted via the phase demodulator 19 to the evaluation unit 20. This voltage is compared with the voltage of a reference coil 21 measured at room temperature (FIG. 3), which is also transmitted to the evaluation unit 20.