GB700633A - Electrical control systems - Google Patents

Abstract

700,633. Automatic flow control systems. BABCOCK & WILCOX CO. March 12, 1951 [March 28, 1950], No. 5901/51. Class 38 (4) In an electrical system for controlling the continuous casting of molten metal in which an effect dependent on rate of pour is measured cyclically and rate of pour is corrected in accordance with each cyclic measurement, each measurement is stored and utilized to effect additional correction after correction in accordance with the next cyclic measurement. In a continuous casting process, steel from a heated vessel 10, Fig. 1, is poured into a tun dish 11 delivering a slag-free stream to a selected position in the open upper end of a liquid cooled mould 12. Beneath mould 12 the casting is engaged by a set of pinch rolls driven by an electric motor 26, water being sprayed on to the casting from jets in a manifold 30. Motor 26, which is operated intermittently to withdraw the casting, and another electric motor, which operates a hoist 18 continuously to maintain flow from vessel 10, are under the control of apparatus 37 which is described with reference to Fig. 2 (not shown) and produces the following system of operation. Motor 26 is started, or increased from a low speed each time the level of molten metal rises sufficiently to influence the effect of radiation from an X-ray tub 33 on an ionization chamber 35, and is stopped, or increased to normal speed, after a run of fixed duration by contacts operated by an electric synchronous motor timer. Each time motor 26 stops a second timer is started which, at the end of a fixed time period, operates a relay. A second relay is operated whenever motor 26 starts, on the level rising again to influence ionization chamber 35. The order of operation of the two relays and the time interval between them is thus a measurement of the sense and magnitude of deviation of the rate of pour from a value determined by the second timer. During the time interval between the operation of the relays, two electric synchronous motor-driven timing rheostats move in opposite directions dependent on the sense of the deviation. One timer rheostat is automatically returned to its datum position after the interval, to time the movement of a motor-driven rheostat correctively adjusting the speed of the hoist motor which thus moves for a time dependent on the deviation. The position of other timer rheostat remains fixed to store the deviation measurement until measurement occurs again during the next cycle. During the next cyclic measurement the timing rheostates are moved in directions opposite from those in which they were moved in the preceding cycle, to an extent dependent on the new measurement of deviation the rheostat which was returned to its datum position after the preceding measurement serving to store the new deviation measurement. The rheostat which stored the preceding deviation measurement is automatically returned to its datum position after its further movement during new measurement to time another movement of the speed adjusting rheostat which is thus also influenced by the deviation measurement of the preceding cycle. The sense of the latter influence is such that if the deviation decreases during successive cycles the amount of adjustment of the speed regulating rheostat is reduced. A clutch may be operated manually to introduce a further speed adjusting rheostat in series with the first which is adjusted in accordance with each cyclic deviation measurement, the adjustment either remaining until the next measurement or being immediately automatically reduced to zero, according to the setting of manually operated switches. A switch may be manually operated to return the control apparatus to a datum condition after a temporary obstruction of flow. Use of temperature or light-sensitive level detectors is referred to.