VHE has developed a new Thimble removing machine

VHE has designed and fabricated a thimble removal press with several novel features. The machine was installed in a smelter in Iceland in mid-2013.

Thimble is associated with the process of aluminium smelting where it forms the metal brushings attached to the anode stems. They are usually made up of cast iron and needs to be removed frequently so that the anode stem can be reused after cleaning and the metal remains of the thimble can be sent to recycling.

The thimble press is designed for use with stubs arranged three in line but may be adapted for other configurations. Uniquely, the design permits the machine to automatically adjust to yokes with different stem offsets, a necessary feature at certain smelters.

When a rod enters the press the stem is clamped with a set of hydraulically operated rollers which permit the secured rod to move vertically during the thimble removal process. Three pairs of hydraulically operated clamps close around the stubs immediately above the thimbles. These clamps have adequate tolerance to accommodate bent stubs.

A single 500mm bore hydraulic cylinder provides the breaking force, moving an anvil head upwards to engage the bottoms of all three thimbles and forcing them against the three pairs of stub clamps, breaking the thimbles. The thimble pieces fall in chutes on either side of the machine from where they are delivered to a discharge conveyor for further processing.

A state-of-the-art hydraulic power pack ensures that adequate pressure and flow is maintained at all times, through the use of two 75 kW motors driving variable displacement pumps.