This dual-stage rotary hearth furnace was built for annealing small aluminium components. The components were dropped into the top buckets in batches, via a small chute. From here they do a lap of the heating section of the furnace before being dropped from that bucket into a lower one, where they do a lap of the cooling level. Then they drop out of that bucket into a container placed below the furnace.

The buckets are driven round by a spider that rotates on a central shaft. The buckets can pivot around their leg of the spider, and do so to discharge their load into the lower level.