Dec 2 2006
Stimir of Iceland has recently completed the design of a Stub Milling Machine for New Zealand Aluminium Smelters.
At pot operating temperatures the weight of the carbon anode causes the steel anode stubs to slowly stretch. Recently repaired stubs have less elongation. During the rodding process, the longest stub will be only one correctly seated in the anode stub hole; an air gap will occur under all other stubs. This air gap will be filled with cast iron, resulting in a thick thimble base, or “pancake”.
This variable thickness of cast iron modifies the electrical properties of each stub, affecting the current distribution throughout the anode. With some types of casting station, the rod may tilt during the rodding operation; the resultant “cocked” anode may not fit correctly in the reduction cell. When the spent anode is processed, thimble stripping can be considerably more difficult with uneven thimble thicknesses.
The contract awared to Stimir by NZAS required Stimir to fully design a Stub Milling Machine able to automatically mill off excess stub length whilst the anode rod is hanging in the overhead conveyor. Stimir successfully completed the engineering and delivered the design to NZAS, together with a cost estimate for the manufacture of the machine.
The use of an automatic stub milling machine to ensure that all stubs are of equal length would result in improved electrical conductivity, better rodded anode geometry, and easier removal of cast iron thimbles. Together, these improved parameters increase electrical efficiency, and maximise both rod availability and rod service life, whilst minimising rod repair costs.
Stimir hf. is a solution provider to the primary aluminium industry, with particular focus on the Rodding Plant. All aspects of design and fabrication are undertaken at Stimir’s own facilities, ensuring total quality control and on-time delivery.