A method to cover the exposures of a bath of molten steel by means of casting powder in an ingot mold of a plant for continuous casting of steel into which, by means of a snorkel disposed in a substantially central position in the mold and connected to a tundish, the molten steel is introduced, comprising:
- detecting zones of exposures of the molten bath of the ingot mold where there is a lack of casting powder by acquiring images and/or video sequences of the surface of the bath of molten steel of the mold to identify said exposures on the basis of their high light intensity with respect to the casting powder;
- subdividing the ingot mold into a plurality of zones (I, II, III, IV, V, VI, VII, VIII, IX, X, XI), with each of which a determinate type of covering movement is associated, performed to distribute the powder on the detected exposures, said zones (I, II, III, IV, V, VI, VII, VIII, IX, X, XI) being determined and identified in a manner coordinated with a position of the snorkel and of an edge of the ingot mold, determining at least zones (I, VIII) distanced from the snorkel and near the edge of the mold, zones (II, III, IV, VI, VII, IX) near the snorkel with respect to the edge of the mold and/or in a position opposite the snorkel with respect to a desired common point (C) of the mold, and at least a zone (V) which is opposite and behind the snorkel with respect to the common point (C);
- automated execution of one or more covering movements by means of which the casting powder is distributed in a selected one of said zones (I, II, III, IV, V, VI, VII, VIII, IX, X, XI), which movements, repeated in sequence according to a desired program, are selected from a group of pouring movements and throwing movements, at least on the basis of a reciprocal position of each of said zones (I, II, III, IV, V, VI, VII, VIII, IX, X, XI) and the snorkel, said covering movements being performed starting from said common point (C) of the mold, displacing the powder from said common point (C) toward an approach point selected to have at least a first spatial coordinate which disposes it on the edge of the mold and a second spatial coordinate in common with the region of the mold in which the zone (I, II, III, IV, V, VI, VII, VIII, IX, X, XI) to be serviced is found, and a final covering movement is performed from said approach point;
- wherein the method provides both a step of displacement into a re-loading position (R) where a step of re-loading the powder is carried out, and also, once the re-loading step is finished, a step of displacement to said desired common point (C) of the ingot mold, from which said covering movements are again carried out;
- said method also providing to discern detected exposures with respect to flames, sparks or other visual disturbances present on the bath of molten steel, effecting:
- applying a technique for temporal non-linear filtering of pixels of the acquired images, based on M-SD (Mean-Standard Deviation) filtering, which provides to calculate development of the mean and standard deviation of the intensity of every pixel, on a temporal window of desired amplitude and a thresholding, wherein the points relating to all the pixels whose mean intensity is higher than a determinate threshold value and whose standard deviation is less than a further determinate threshold value are considered exposed.