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The design principles and the technical and working characteristics are presented for a series of ovens of capacity 250 -500 kVA, which are intended for producing basalt wool and ferrous alloys.The constantly increasing prices for energy have caused a rise in the demand for efficient refractory and thermal-insulation materials, in particular ones based on basalt wool. They are much better than insulating materials made of mineral wool and glass fiber, which do not meet current specifications for ecology, hygroscopicity, and working life.The VOSTIO Company has developed a single-stage high-throughput method of making staple basalt fiber by the use of arc furnaces. Lines have been designed and built for producing basalt fiber materials.The apparatus for making these fibers is a continuousacting flow line and includes an arc furnace, together with built-in facilities for producing the liquid as a water-cooled substance, a fiber-forming space consisting of a diffuser, horizontal chamber for fiber deposition with grid conveyor, and units for cutting and reeling the material.The Eloterm Company has used the VOSTIO Company technical specifications in a series of ovens of capacity 250 -500 kVA intended for the production of ultrathin basalt fiber.An advantage of a small electric furnace for melting basalt raw material by comparison with large ones is due to the following factors: 1) the scope for electrical supply from a line at 380 V or from a gas generator, which does not require high-power furnace substations, or the use of expensive furnace transformers with oil cooling and corresponding high-voltage equipment;2) much less consumption of cooling water;3) scope for placing the equipment in small areas in buildings with relatively small clearance from overhead cranes; 4) lack of need for expensive high-power fans and dust-trapping equipment, which are characteristic of organizations that operate high-power furnaces of this type; 5) short shutdowns associated with stopping the work of the furnace for current or emergency repair; and 6) smaller numbers of service staff. This means that small electric furnaces are particularly effective in regions with relatively poor energy supplies, and at organizations that use heat-insulating and refractory materials for their own purposes, and also at small organizations providing for the needs of local users. Table 1 gives the basic technical characteristics of this furnace series.The melting vessel in each of the furnaces is an internally lined steel framework made of welded rectangular panels. In an RPO-0.25 single-phase two-electrode furnace, the melting vessel is rectangular in cross section, while in the three-phase furnaces RPO-0.25I3 and RPO-0.5, it is hexagonal. At the outer surfaces of the side panels there are water-cooling channels formed by standard channeling welded to the panels.There is a difference from the RPO-0.25 and RPO-0.25I2 batch furnaces in that the melting vessel in the RPZ-0.5 has a water-cooled lid with sand cover, three electrode holes and a loading tube ...