1, Crack inspection uses a steel ruler with a scale up to 0.5 millimeters and a steel wire with a diameter equal to the measured crack width (e.g. 0.1, 0.25, 0.5, 1.0 millimeters);
2, When checking for cracks in high alumina bricks, insert the steel wire naturally into the wide area of the crack But it shall not be inserted into the visible particle detachment site; Any crack that cannot be inserted into a 0.25mm steel wire is represented by a width less than 0.25mm; For cracks where 0.25mm steel wire can be inserted but 0.5mm steel wire cannot be inserted, the width is represented by 0.25-0.5mm, and so on;
3, When the crack does not form a straight line, it can be measured in segments, and the total length of each segment is the total length of the crack; Cracks with interruptions in the middle and a distance of less than 5 millimeters between them (including unrestricted cracks) are considered as one crack, and their lengths are calculated together, except for intersecting and parallel cracks;
4, Cross edge cracks, except for special circumstances, shall be calculated as continuous cracks. If a crack crosses both the working face and non working face at the same time, it shall be calculated as a working face; Cracks that span two edges at the corner and do not exceed the range specified for missing corners shall not be calculated as spanning two edges; Any cracks that are restricted by the standards are not subject to cross edge restrictions and will not be inspected;
5, The surface with grooves and convex edges shall be calculated as one surface, except for high alumina bricks used for casting; For surfaces with through holes, calculate based on two surfaces;
6, High alumina bricks that form thin and long straight cracks due to improper cooling are considered cold cracks and should be treated as non-conforming products;
7, A closed curve formed by several cracks is called a network crack; When calculating the length of a mesh crack, the total length of the surrounding area shall prevail; If more than one crack intersects, it is called a cross crack; When calculating the number of intersecting cracks, the straight cracks shall prevail;
8, Edges with a 120 degree angle are not counted as edges, and surfaces with dimensions less than 20 millimeters are not counted as surfaces, except for high alumina bricks used for casting.
High alumina brick is a common refractory material with high refractoriness, mainly used for lining blast furnaces, hot blast stoves, electric furnace tops, blast furnaces, reverberatory furnaces, and rotary kilns.
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