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Fibrous refractory materials give efficient high-temperature heat insulation in heat-using equipment. The USSR produces kaolin and high-alumina refractory fibers [1] and heat-insulation panels of kaolin and highalumina wool [2]. An extension of the range of fibrous refractory heat-insulation products will make it possible to exploit more fully the advantages offered by these materials.Tubes are manufactured from ceramic fibers by in-vacuo forming [3] and by the layerwise deposition of ceramic-fiber paper with a bonding substance* The Ukrainian Scientific-Research Institute of Refractories jointly with the Bogdanovich Refractories Plant and the Sukholozhsk Combine of Asbestos-Cement Products have produced experimental batches of heat-insulation tubes from high-alumina wool with an inorganic binder.The tubes were produced on standard equipment at the Sukholozhsk Combine of Asbestos-Cement Products. The production line included a hydraulic mixer, a hollander, a service tank, and an ATM-3 type asbestos-tube forming machine with a conveyer and drying chamber.The tubes were manufactured from high-alumina wool (TU-14-8-107-74) produced by the Bogdanovich Refractories Plant. The inorganic binder was prepared in the hydraulic mixer after which the high-alumina wool was added. The components were mixed for 10-15 min after which the composition was pumped to the hollander and then conveyed through a service mixer to the tube-forming machine.The process of forming tubes from the composition based onhigh-ainmina wool did not differ significantly from that of producing asbestos-cement tubes. The film was not damaged during the transfer to the web and was easily detached from the lattice cylinder, and the newly formed tubes contained no faults and were removed from the ram without difficulties.The moisture content of the mix on the web was 55% before and 42% after the vacuum treatment. The thickness of the film was 0.2 mm and the moisture content of the fresh-formed tube 24%. The tubes were dried for 18 h in a drying chamber at 65-75~The tube dimensions are: length, 3000 ram; inside diameter, 110 and 145 mm; and wall thickness, 10-25 mm. The chemical composition of the finished product is as follows: 38.12%SIO 2, 33.7670 AI203, 0.44% Fe203, 11.74% CaO, 1.64% MgO, 0.95% K20, 0.51% Na20, and 1.08% SOs; calcination loss 11.76%. The apparent density of the products is 450 kg/m 3.Petrographic analyses# showed that the product consists of a fibrous glasslike material with refractive indices 1.545&0.003, which is that of high alumina refractory fiber, and a dispersed anisotropic substance on a calcium silicate base.

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