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 width of the crack. However, it should not be inserted into the visible particle detachment area; Any crack that cannot be inserted by a 0.25mm steel wire, its width is expressed as less than 0.25mm; Any crack that can be inserted with 0.25mm steel wire but cannot be inserted with 0.5mm steel wire, its width is expressed as 0.25-0.5mm, and so on;
3) When the crack is not in a straight line, it can be measured in segments, and the total length of each segment is the total length of the crack; A crack with a gap in the middle and a gap distance of less than 5 millimeters (including unrestricted cracks) is considered a crack, and its length is calculated together, except for intersecting and parallel cracks;
4) Cross edge cracks, except in special cases, are all calculated as continuous cracks. If a crack spans both working and non working surfaces, it is all calculated as working surfaces; Cracks that span two edges at the corner shall not be calculated as spanning two edges if they do not exceed the specified value range of the missing angle; Cracks that are subject to the limitations specified in the standard are not subject to cross edge limitations and are not subject to inspection;
5) For surfaces with grooves and protrusions, they shall be calculated as one surface, except for high alumina bricks used for casting; For surfaces with through holes, calculate as two surfaces;
6) High alumina bricks form thin and long straight cracks due to improper cooling, which are cold cracks and should be treated as unqualified products;
7) A closed curve formed by several cracks is called a network crack; When calculating the length of network cracks, the total length of the periphery shall prevail; Where more than one crack intersects, it is called a intersecting crack; When calculating the number of intersecting cracks, use straight cracks as the standard;
8) Edges with a 120 degree angle are not counted as edges, and faces with dimensions less than 20 millimeters are not counted as faces, except for high alumina bricks used for casting.
We know that high alumina bricks are a common refractory material with high fire resistance, mainly used for lining blast furnaces, hot blast furnaces, electric furnace tops, blast furnaces, reverberators, and rotary kilns.
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