Lining of Tapping Spouts. Until recently, the refractory for the inside surfaces of the spouts of the open-hearth furnaces at the Nizhnedneprovsk Pipe Plant (NPP) was applied manually --with trowels. The solution for the dry refractory powder was prepared in a mechanical mixer. Here a periclase-chromite mixture was bound with an aqueous solution of iron sulfate. The life of the resulting spout lining was low, and sections of the lining would often be washed away during tapping, allowing burn-through of the body of the spout. Also, the working conditions for the refractory installers putting in the linings were difficult.To solve these problems, the central automation and mechanization lab at the NPP, following the experience of the Zaporozhstal' combine, developed and introduced a unit for guniting the inside surfaces of the spouts with a refractory composition. The lab performed tests to determine the most effective refractory and binding solution. It was found that the most durable lining is obtained with the use of refractories of the SKhP or "Slute" type when slaked by an aqueous solution of iron sulfate or sodium tripolyphosphate.The unit for guniting the spout lining consists of two refractory storage tanks, an SB-67 machine for casing-less guniting, a tank to prepare the aqueous solution of iron sulfate~ a tank for the finished solution, a pumping unit, a mixing chamber, a line to deliver the finished refractory with an inside diameter of 40 mm, a cantilever suspension for the line, and pneumatic and electrical control systems.The unit works as follows. A vibrating feeder moves the dry refractory composition from the storage bins to the SB-67 guniting machine through a guide chute with a screen; an aqueous solution of iron sulfate with a density of 1.24-1.26 g/cm 3 is prepared in the f'trst tank and sent to the intermediate tank. The cavity of the SB-67 guniting machine is closed off by a special bell-shaped valve, and compressed air under a pressure of 0.4 MPa is sent into the pneumatic system of the machine. The batcher of the machine and the pumping unit are turned on simultaneously. Then the dry refractory is sent through the mixing chamber into the line. When a steady-state flow of refractory is established, the aqueous solution of iron sulfate is transferred to the mixing chamber at a pressure exceeding the pressure of the refractory. A refractory composition of the required density is formed in this chamber. The refractory proceeds from the chamber into the spout under high pressure, so that its application in circular motions on the spout f'dls all of the discontinuities in the brick and produces a stronger lining. After guniting is completed, the feed of aqueous iron sulfite solution to the mixing chamber is cut off. Then the supply of dry refractory is also stopped. The line is blown out with compressed air and the unit is ready for a new cycle of operation. The productivity of the machine in terms of dry refractory is 4 m3/h, and it takes 4-6 min to gunite one spout.Introduction of the new techn...
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