Rotary-Ring Furnace

an industrial furnace in which articles are heated on a rotating annular hearth. Rotary-ring furnaces are mainly used for heating billets in the rolling of pipes, wheels, and the tread bands of railroad rolling stock, for heat treatment of metal items, and for heating nonferrous metal billets prior to rolling and upsetting. The first rotary-ring furnace was developed in 1925 by the Soviet inventor N. D. Bulin.

Rotary-ring furnaces consist of a rotating hearth and a fixed annular channel covered by a vault. The ring-shaped slits between the rotating hearth and the fixed part of the furnace are packed with water seals. The articles are charged and unloaded through doors using special floor-mounted or overhead loading and unloading machines. The working space of the furnace between the doors is divided by a heat-resistant barrier. In small rotary-ring furnaces, items are charged and unloaded through the same door. The hearth is rotated on supporting rollers by an electric drive.

The outside diameter of rotary-ring furnaces is 10–30m, the hearth width is 1.5–6.0 m, and their output is up to 75 tons per hr. The heating zones and temperature regimes of large rotary-ring furnaces are the same as for holding furnaces. Small rotary-ring furnaces operate at a constant temperature throughout the entire furnace volume. Rotary-ring furnaces are heated by gas or liquid fuel. For furnace diameters of 10–12 m, the burners are placed only on the outer wall; for larger diameters, they are mounted on both the outer and inner walls.